Merge pull request #319 from duysqubix/master

Update README.md

CHANGELOG.md

@@ -5,7 +5,35 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
-- Upgrade to GLFW 3.3
+- Add AnchorPos struct and functions #252
+- Add Clipboard Support
+- Fix SIGSEGV on text.NewAtlas if glyph absent 
+- Use slice for range in Drawer.Dirty(), to improve performance
+- GLTriangle's fragment shader is used when rendered by the Canvas.
+- Add MSAA support
+
+## [v0.10.0] 2020-08-22
+- Add AnchorPos struct and functions
+- Gamepad API added
+- Support setting an initial window position
+- Support hiding the window initially
+- Support creating maximized windows
+- Support waiting for events to reduce CPU load
+- Adding clipping rectangle support in GLTriangles
+
+## [v0.10.0-beta] 2020-05-10
+- Add `WindowConfig.TransparentFramebuffer` option to support window transparency onto the background
+- Fixed Line intersects failing on lines passing through (0, 0)
+
+## [v0.10.0-alpha] 2020-05-08
+- Upgrade to GLFW 3.3! :tada:
+  - Closes https://github.com/faiface/pixel/issues/137
+- Add support for glfw's DisableCursor
+  - Closes https://github.com/faiface/pixel/issues/213
+
+## [v0.9.0] - 2020-05-02
+- Added feature from https://github.com/faiface/pixel/pull/219
+  - Exposing Window.SwapBuffers so buffers can be swapped without polling input
 - Add more examples
 - Add position as out variable from vertex shader
 - Add experimental joystick support
@@ -22,9 +50,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add support for Go Modules
 - Add `NoIconify` and `AlwaysOnTop` window hints
 
+
 ## [v0.8.0] - 2018-10-10
 Changelog for this and older versions can be found on the corresponding [GitHub
 releases](https://github.com/faiface/pixel/releases).
 
-[Unreleased]: https://github.com/faiface/pixel/compare/v0.8.0...HEAD
+[Unreleased]: https://github.com/faiface/pixel/compare/v0.10.0...HEAD
+[v0.10.0]: https://github.com/faiface/pixel/compare/v0.10.0-beta...v0.10.0
+[v0.10.0-beta]: https://github.com/faiface/pixel/compare/v0.10.0-alpha...v0.10.0-beta
+[v0.10.0-alpha]: https://github.com/faiface/pixel/compare/v0.9.0...v0.10.0-alpha
+[v0.9.0]: https://github.com/faiface/pixel/compare/v0.8.0...v0.9.0
 [v0.8.0]: https://github.com/faiface/pixel/releases/tag/v0.8.0

CONTRIBUTING.md

@@ -7,7 +7,7 @@
 1. **Make a community example** and place it inside the `community` folder of the [examples repository][examples].
 2. **Add tests**. There only few tests in Pixel at the moment. Take a look at them and make some similar.
 3. **Add a small feature or an improvement**. Feel like some small feature is missing? Just make a PR. Be ready that I might reject it, though, if I don't find it particularly appealing.
-4. **Join the big development** by joining the discussion at the [Gitter](https://gitter.im/pixellib/Lobby), where we can discuss bigger changes and implement them after that.
+4. **Join the big development** by joining the discussion on our [Discord Server](https://discord.gg/q2DK4MP), where we can discuss bigger changes and implement them after that.
 
 ## How to make a pull request
 

README.md

@@ -1,3 +1,9 @@
+# \*\*\*\*\*NOTICE\*\*\*\*\* 
+
+This repo is not under active development anymore and has been archived. Continued development has been migrated to [Pixel2](https://github.com/gopxl/pixel). A big thank you to [faiface](https://github.com/faiface) for creating this awesome library and for all the hard work put into it. We encourage old and new users to check out the new repo and contribute to it.
+
+
+
 <p align="center"><img src="logo/LOGOTYPE-HORIZONTAL-BLUE.png"></p>
 
 # Pixel [![Build Status](https://travis-ci.org/faiface/pixel.svg?branch=master)](https://travis-ci.org/faiface/pixel) [![GoDoc](https://godoc.org/github.com/faiface/pixel?status.svg)](https://godoc.org/github.com/faiface/pixel) [![Go Report Card](https://goreportcard.com/badge/github.com/faiface/pixel)](https://goreportcard.com/report/github.com/faiface/pixel) [![Join the chat at https://gitter.im/pixellib/Lobby](https://badges.gitter.im/pixellib/Lobby.svg)](https://gitter.im/pixellib/Lobby?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![Discord Chat](https://img.shields.io/discord/699679031603494954)](https://discord.gg/q2DK4MP)  
@@ -108,8 +114,10 @@ Here's the list of the main features in Pixel. Although Pixel is still under hea
  ## Related repositories
 
  Here are some packages which use Pixel:
- - [TilePix](https://github.com/bcvery1/tilepix) Makes handling TMX files built with [Tiled](https://www.mapeditor.org/)
+ - [TilePix](https://github.com/bcvery1/tilepix) Makes handling TMX files built with [Tiled](https://www.mapeditor.org/) trivially easy to work with using Pixel.
- trivially easy to work with using Pixel.
+ - [spriteplus](https://github.com/cebarks/spriteplus) Basic `SpriteSheet` and `Animation` implementations
+ - [PixelUI](https://github.com/dusk125/pixelui) Imgui-based GUIs for Pixel
+ - [pixelutils](https://github.com/dusk125/pixelutils) Variety of game related utilities (sprite packer, id generator, ticker, sprite loader, voronoia diagrams)
 
 ## Missing features
 
@@ -144,7 +152,7 @@ The OpenGL version used is **OpenGL 3.3**.
   headers and libraries.
 - On Ubuntu/Debian-like Linux distributions, you need `libgl1-mesa-dev` and `xorg-dev` packages.
 - On CentOS/Fedora-like Linux distributions, you need `libX11-devel libXcursor-devel libXrandr-devel
-  libXinerama-devel mesa-libGL-devel libXi-devel` packages.
+  libXinerama-devel mesa-libGL-devel libXi-devel libXxf86vm-devel` packages.
 - See [here](http://www.glfw.org/docs/latest/compile.html#compile_deps) for full details.
 
 **The combination of Go 1.8, macOS and latest XCode seems to be problematic** as mentioned in issue
@@ -153,6 +161,8 @@ The OpenGL version used is **OpenGL 3.3**.
 
 ## Contributing
 
+Join us in the [Discord Chat!](https://discord.gg/q2DK4MP)
+
 Pixel is in, let's say, mid-stage of development. Many of the important features are here, some are
 missing. That's why **contributions are very important and welcome!** All alone, I will be able to
 finish the library, but it'll take a lot of time. With your help, it'll take much less. I encourage
@@ -170,10 +180,6 @@ better result.
 
 Take a look at [CONTRIBUTING.md](CONTRIBUTING.md) for further information.
 
-For any kind of discussion, feel free to use our
-[Gitter](https://gitter.im/pixellib/Lobby)
-community.
-
 ## License
 
 [MIT](LICENSE)

batch.go

@@ -26,7 +26,7 @@ var _ BasicTarget = (*Batch)(nil)
 //
 // Note, that if the container does not support TrianglesColor, color masking will not work.
 func NewBatch(container Triangles, pic Picture) *Batch {
-	b := &Batch{cont: Drawer{Triangles: container, Picture: pic}}
+	b := &Batch{cont: Drawer{Triangles: container, Picture: pic, Cached: true}}
 	b.SetMatrix(IM)
 	b.SetColorMask(Alpha(1))
 	return b

circle.go

@@ -0,0 +1,334 @@
+package pixel
+
+import (
+	"fmt"
+	"math"
+)
+
+// Circle is a 2D circle. It is defined by two properties:
+//  - Center vector
+//  - Radius float64
+type Circle struct {
+	Center Vec
+	Radius float64
+}
+
+// C returns a new Circle with the given radius and center coordinates.
+//
+// Note that a negative radius is valid.
+func C(center Vec, radius float64) Circle {
+	return Circle{
+		Center: center,
+		Radius: radius,
+	}
+}
+
+// String returns the string representation of the Circle.
+//
+//  c := pixel.C(10.1234, pixel.ZV)
+//  c.String()     // returns "Circle(10.12, Vec(0, 0))"
+//  fmt.Println(c) // Circle(10.12, Vec(0, 0))
+func (c Circle) String() string {
+	return fmt.Sprintf("Circle(%s, %.2f)", c.Center, c.Radius)
+}
+
+// Norm returns the Circle in normalized form - this sets the radius to its absolute value.
+//
+// c := pixel.C(-10, pixel.ZV)
+// c.Norm() // returns pixel.Circle{pixel.Vec{0, 0}, 10}
+func (c Circle) Norm() Circle {
+	return Circle{
+		Center: c.Center,
+		Radius: math.Abs(c.Radius),
+	}
+}
+
+// Area returns the area of the Circle.
+func (c Circle) Area() float64 {
+	return math.Pi * math.Pow(c.Radius, 2)
+}
+
+// Moved returns the Circle moved by the given vector delta.
+func (c Circle) Moved(delta Vec) Circle {
+	return Circle{
+		Center: c.Center.Add(delta),
+		Radius: c.Radius,
+	}
+}
+
+// Resized returns the Circle resized by the given delta.  The Circles center is use as the anchor.
+//
+// c := pixel.C(pixel.ZV, 10)
+// c.Resized(-5) // returns pixel.Circle{pixel.Vec{0, 0}, 5}
+// c.Resized(25) // returns pixel.Circle{pixel.Vec{0, 0}, 35}
+func (c Circle) Resized(radiusDelta float64) Circle {
+	return Circle{
+		Center: c.Center,
+		Radius: c.Radius + radiusDelta,
+	}
+}
+
+// Contains checks whether a vector `u` is contained within this Circle (including it's perimeter).
+func (c Circle) Contains(u Vec) bool {
+	toCenter := c.Center.To(u)
+	return c.Radius >= toCenter.Len()
+}
+
+// Formula returns the values of h and k, for the equation of the circle: (x-h)^2 + (y-k)^2 = r^2
+// where r is the radius of the circle.
+func (c Circle) Formula() (h, k float64) {
+	return c.Center.X, c.Center.Y
+}
+
+// maxCircle will return the larger circle based on the radius.
+func maxCircle(c, d Circle) Circle {
+	if c.Radius < d.Radius {
+		return d
+	}
+	return c
+}
+
+// minCircle will return the smaller circle based on the radius.
+func minCircle(c, d Circle) Circle {
+	if c.Radius < d.Radius {
+		return c
+	}
+	return d
+}
+
+// Union returns the minimal Circle which covers both `c` and `d`.
+func (c Circle) Union(d Circle) Circle {
+	biggerC := maxCircle(c.Norm(), d.Norm())
+	smallerC := minCircle(c.Norm(), d.Norm())
+
+	// Get distance between centers
+	dist := c.Center.To(d.Center).Len()
+
+	// If the bigger Circle encompasses the smaller one, we have the result
+	if dist+smallerC.Radius <= biggerC.Radius {
+		return biggerC
+	}
+
+	// Calculate radius for encompassing Circle
+	r := (dist + biggerC.Radius + smallerC.Radius) / 2
+
+	// Calculate center for encompassing Circle
+	theta := .5 + (biggerC.Radius-smallerC.Radius)/(2*dist)
+	center := Lerp(smallerC.Center, biggerC.Center, theta)
+
+	return Circle{
+		Center: center,
+		Radius: r,
+	}
+}
+
+// Intersect returns the maximal Circle which is covered by both `c` and `d`.
+//
+// If `c` and `d` don't overlap, this function returns a zero-sized circle at the centerpoint between the two Circle's
+// centers.
+func (c Circle) Intersect(d Circle) Circle {
+	// Check if one of the circles encompasses the other; if so, return that one
+	biggerC := maxCircle(c.Norm(), d.Norm())
+	smallerC := minCircle(c.Norm(), d.Norm())
+
+	if biggerC.Radius >= biggerC.Center.To(smallerC.Center).Len()+smallerC.Radius {
+		return biggerC
+	}
+
+	// Calculate the midpoint between the two radii
+	// Distance between centers
+	dist := c.Center.To(d.Center).Len()
+	// Difference between radii
+	diff := dist - (c.Radius + d.Radius)
+	// Distance from c.Center to the weighted midpoint
+	distToMidpoint := c.Radius + 0.5*diff
+	// Weighted midpoint
+	center := Lerp(c.Center, d.Center, distToMidpoint/dist)
+
+	// No need to calculate radius if the circles do not overlap
+	if c.Center.To(d.Center).Len() >= c.Radius+d.Radius {
+		return C(center, 0)
+	}
+
+	radius := c.Center.To(d.Center).Len() - (c.Radius + d.Radius)
+
+	return Circle{
+		Center: center,
+		Radius: math.Abs(radius),
+	}
+}
+
+// IntersectLine will return the shortest Vec such that if the Circle is moved by the Vec returned, the Line and Rect no
+// longer intersect.
+func (c Circle) IntersectLine(l Line) Vec {
+	return l.IntersectCircle(c).Scaled(-1)
+}
+
+// IntersectRect returns a minimal required Vector, such that moving the circle by that vector would stop the Circle
+// and the Rect intersecting.  This function returns a zero-vector if the Circle and Rect do not overlap, and if only
+// the perimeters touch.
+//
+// This function will return a non-zero vector if:
+//  - The Rect contains the Circle, partially or fully
+//  - The Circle contains the Rect, partially of fully
+func (c Circle) IntersectRect(r Rect) Vec {
+	// Checks if the c.Center is not in the diagonal quadrants of the rectangle
+	if (r.Min.X <= c.Center.X && c.Center.X <= r.Max.X) || (r.Min.Y <= c.Center.Y && c.Center.Y <= r.Max.Y) {
+		// 'grow' the Rect by c.Radius in each orthagonal
+		grown := Rect{Min: r.Min.Sub(V(c.Radius, c.Radius)), Max: r.Max.Add(V(c.Radius, c.Radius))}
+		if !grown.Contains(c.Center) {
+			// c.Center not close enough to overlap, return zero-vector
+			return ZV
+		}
+
+		// Get minimum distance to travel out of Rect
+		rToC := r.Center().To(c.Center)
+		h := c.Radius - math.Abs(rToC.X) + (r.W() / 2)
+		v := c.Radius - math.Abs(rToC.Y) + (r.H() / 2)
+
+		if rToC.X < 0 {
+			h = -h
+		}
+		if rToC.Y < 0 {
+			v = -v
+		}
+
+		// No intersect
+		if h == 0 && v == 0 {
+			return ZV
+		}
+
+		if math.Abs(h) > math.Abs(v) {
+			// Vertical distance shorter
+			return V(0, v)
+		}
+		return V(h, 0)
+	} else {
+		// The center is in the diagonal quadrants
+
+		// Helper points to make code below easy to read.
+		rectTopLeft := V(r.Min.X, r.Max.Y)
+		rectBottomRight := V(r.Max.X, r.Min.Y)
+
+		// Check for overlap.
+		if !(c.Contains(r.Min) || c.Contains(r.Max) || c.Contains(rectTopLeft) || c.Contains(rectBottomRight)) {
+			// No overlap.
+			return ZV
+		}
+
+		var centerToCorner Vec
+		if c.Center.To(r.Min).Len() <= c.Radius {
+			// Closest to bottom-left
+			centerToCorner = c.Center.To(r.Min)
+		}
+		if c.Center.To(r.Max).Len() <= c.Radius {
+			// Closest to top-right
+			centerToCorner = c.Center.To(r.Max)
+		}
+		if c.Center.To(rectTopLeft).Len() <= c.Radius {
+			// Closest to top-left
+			centerToCorner = c.Center.To(rectTopLeft)
+		}
+		if c.Center.To(rectBottomRight).Len() <= c.Radius {
+			// Closest to bottom-right
+			centerToCorner = c.Center.To(rectBottomRight)
+		}
+
+		cornerToCircumferenceLen := c.Radius - centerToCorner.Len()
+
+		return centerToCorner.Unit().Scaled(cornerToCircumferenceLen)
+	}
+}
+
+// IntersectionPoints returns all the points where the Circle intersects with the line provided.  This can be zero, one or
+// two points, depending on the location of the shapes.  The points of intersection will be returned in order of
+// closest-to-l.A to closest-to-l.B.
+func (c Circle) IntersectionPoints(l Line) []Vec {
+	cContainsA := c.Contains(l.A)
+	cContainsB := c.Contains(l.B)
+
+	// Special case for both endpoint being contained within the circle
+	if cContainsA && cContainsB {
+		return []Vec{}
+	}
+
+	// Get closest point on the line to this circles' center
+	closestToCenter := l.Closest(c.Center)
+
+	// If the distance to the closest point is greater than the radius, there are no points of intersection
+	if closestToCenter.To(c.Center).Len() > c.Radius {
+		return []Vec{}
+	}
+
+	// If the distance to the closest point is equal to the radius, the line is tangent and the closest point is the
+	// point at which it touches the circle.
+	if closestToCenter.To(c.Center).Len() == c.Radius {
+		return []Vec{closestToCenter}
+	}
+
+	// Special case for endpoint being on the circles' center
+	if c.Center == l.A || c.Center == l.B {
+		otherEnd := l.B
+		if c.Center == l.B {
+			otherEnd = l.A
+		}
+		intersect := c.Center.Add(c.Center.To(otherEnd).Unit().Scaled(c.Radius))
+		return []Vec{intersect}
+	}
+
+	// This means the distance to the closest point is less than the radius, so there is at least one intersection,
+	// possibly two.
+
+	// If one of the end points exists within the circle, there is only one intersection
+	if cContainsA || cContainsB {
+		containedPoint := l.A
+		otherEnd := l.B
+		if cContainsB {
+			containedPoint = l.B
+			otherEnd = l.A
+		}
+
+		// Use trigonometry to get the length of the line between the contained point and the intersection point.
+		// The following is used to describe the triangle formed:
+		//  - a is the side between contained point and circle center
+		//  - b is the side between the center and the intersection point (radius)
+		//  - c is the side between the contained point and the intersection point
+		// The captials of these letters are used as the angles opposite the respective sides.
+		// a and b are known
+		a := containedPoint.To(c.Center).Len()
+		b := c.Radius
+		// B can be calculated by subtracting the angle of b (to the x-axis) from the angle of c (to the x-axis)
+		B := containedPoint.To(c.Center).Angle() - containedPoint.To(otherEnd).Angle()
+		// Using the Sin rule we can get A
+		A := math.Asin((a * math.Sin(B)) / b)
+		// Using the rule that there are 180 degrees (or Pi radians) in a triangle, we can now get C
+		C := math.Pi - A + B
+		// If C is zero, the line segment is in-line with the center-intersect line.
+		var c float64
+		if C == 0 {
+			c = b - a
+		} else {
+			// Using the Sine rule again, we can now get c
+			c = (a * math.Sin(C)) / math.Sin(A)
+		}
+		// Travelling from the contained point to the other end by length of a will provide the intersection point.
+		return []Vec{
+			containedPoint.Add(containedPoint.To(otherEnd).Unit().Scaled(c)),
+		}
+	}
+
+	// Otherwise the endpoints exist outside of the circle, and the line segment intersects in two locations.
+	// The vector formed by going from the closest point to the center of the circle will be perpendicular to the line;
+	// this forms a right-angled triangle with the intersection points, with the radius as the hypotenuse.
+	// Calculate the other triangles' sides' length.
+	a := math.Sqrt(math.Pow(c.Radius, 2) - math.Pow(closestToCenter.To(c.Center).Len(), 2))
+
+	// Travelling in both directions from the closest point by length of a will provide the two intersection points.
+	first := closestToCenter.Add(closestToCenter.To(l.A).Unit().Scaled(a))
+	second := closestToCenter.Add(closestToCenter.To(l.B).Unit().Scaled(a))
+
+	if first.To(l.A).Len() < second.To(l.A).Len() {
+		return []Vec{first, second}
+	}
+	return []Vec{second, first}
+}

circle_test.go

@@ -0,0 +1,466 @@
+package pixel_test
+
+import (
+	"math"
+	"reflect"
+	"testing"
+
+	"github.com/faiface/pixel"
+)
+
+func TestC(t *testing.T) {
+	type args struct {
+		radius float64
+		center pixel.Vec
+	}
+	tests := []struct {
+		name string
+		args args
+		want pixel.Circle
+	}{
+		{
+			name: "C(): positive radius",
+			args: args{radius: 10, center: pixel.ZV},
+			want: pixel.Circle{Radius: 10, Center: pixel.ZV},
+		},
+		{
+			name: "C(): zero radius",
+			args: args{radius: 0, center: pixel.ZV},
+			want: pixel.Circle{Radius: 0, Center: pixel.ZV},
+		},
+		{
+			name: "C(): negative radius",
+			args: args{radius: -5, center: pixel.ZV},
+			want: pixel.Circle{Radius: -5, Center: pixel.ZV},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := pixel.C(tt.args.center, tt.args.radius); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("C() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_String(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   string
+	}{
+		{
+			name:   "Circle.String(): positive radius",
+			fields: fields{radius: 10, center: pixel.ZV},
+			want:   "Circle(Vec(0, 0), 10.00)",
+		},
+		{
+			name:   "Circle.String(): zero radius",
+			fields: fields{radius: 0, center: pixel.ZV},
+			want:   "Circle(Vec(0, 0), 0.00)",
+		},
+		{
+			name:   "Circle.String(): negative radius",
+			fields: fields{radius: -5, center: pixel.ZV},
+			want:   "Circle(Vec(0, 0), -5.00)",
+		},
+		{
+			name:   "Circle.String(): irrational radius",
+			fields: fields{radius: math.Pi, center: pixel.ZV},
+			want:   "Circle(Vec(0, 0), 3.14)",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.String(); got != tt.want {
+				t.Errorf("Circle.String() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Norm(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   pixel.Circle
+	}{
+		{
+			name:   "Circle.Norm(): positive radius",
+			fields: fields{radius: 10, center: pixel.ZV},
+			want:   pixel.C(pixel.ZV, 10),
+		},
+		{
+			name:   "Circle.Norm(): zero radius",
+			fields: fields{radius: 0, center: pixel.ZV},
+			want:   pixel.C(pixel.ZV, 0),
+		},
+		{
+			name:   "Circle.Norm(): negative radius",
+			fields: fields{radius: -5, center: pixel.ZV},
+			want:   pixel.C(pixel.ZV, 5),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.Norm(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Circle.Norm() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Area(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   float64
+	}{
+		{
+			name:   "Circle.Area(): positive radius",
+			fields: fields{radius: 10, center: pixel.ZV},
+			want:   100 * math.Pi,
+		},
+		{
+			name:   "Circle.Area(): zero radius",
+			fields: fields{radius: 0, center: pixel.ZV},
+			want:   0,
+		},
+		{
+			name:   "Circle.Area(): negative radius",
+			fields: fields{radius: -5, center: pixel.ZV},
+			want:   25 * math.Pi,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.Area(); got != tt.want {
+				t.Errorf("Circle.Area() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Moved(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	type args struct {
+		delta pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Circle
+	}{
+		{
+			name:   "Circle.Moved(): positive movement",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{delta: pixel.V(10, 20)},
+			want:   pixel.C(pixel.V(10, 20), 10),
+		},
+		{
+			name:   "Circle.Moved(): zero movement",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{delta: pixel.ZV},
+			want:   pixel.C(pixel.V(0, 0), 10),
+		},
+		{
+			name:   "Circle.Moved(): negative movement",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{delta: pixel.V(-5, -10)},
+			want:   pixel.C(pixel.V(-5, -10), 10),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.Moved(tt.args.delta); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Circle.Moved() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Resized(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	type args struct {
+		radiusDelta float64
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Circle
+	}{
+		{
+			name:   "Circle.Resized(): positive delta",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{radiusDelta: 5},
+			want:   pixel.C(pixel.V(0, 0), 15),
+		},
+		{
+			name:   "Circle.Resized(): zero delta",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{radiusDelta: 0},
+			want:   pixel.C(pixel.V(0, 0), 10),
+		},
+		{
+			name:   "Circle.Resized(): negative delta",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{radiusDelta: -5},
+			want:   pixel.C(pixel.V(0, 0), 5),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.Resized(tt.args.radiusDelta); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Circle.Resized() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Contains(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	type args struct {
+		u pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   bool
+	}{
+		{
+			name:   "Circle.Contains(): point on cicles' center",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{u: pixel.ZV},
+			want:   true,
+		},
+		{
+			name:   "Circle.Contains(): point offcenter",
+			fields: fields{radius: 10, center: pixel.V(5, 0)},
+			args:   args{u: pixel.ZV},
+			want:   true,
+		},
+		{
+			name:   "Circle.Contains(): point on circumference",
+			fields: fields{radius: 10, center: pixel.V(10, 0)},
+			args:   args{u: pixel.ZV},
+			want:   true,
+		},
+		{
+			name:   "Circle.Contains(): point outside circle",
+			fields: fields{radius: 10, center: pixel.V(15, 0)},
+			args:   args{u: pixel.ZV},
+			want:   false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.Contains(tt.args.u); got != tt.want {
+				t.Errorf("Circle.Contains() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Union(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	type args struct {
+		d pixel.Circle
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Circle
+	}{
+		{
+			name:   "Circle.Union(): overlapping circles",
+			fields: fields{radius: 5, center: pixel.ZV},
+			args:   args{d: pixel.C(pixel.ZV, 5)},
+			want:   pixel.C(pixel.ZV, 5),
+		},
+		{
+			name:   "Circle.Union(): separate circles",
+			fields: fields{radius: 1, center: pixel.ZV},
+			args:   args{d: pixel.C(pixel.V(0, 2), 1)},
+			want:   pixel.C(pixel.V(0, 1), 2),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(tt.fields.center, tt.fields.radius)
+			if got := c.Union(tt.args.d); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Circle.Union() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_Intersect(t *testing.T) {
+	type fields struct {
+		radius float64
+		center pixel.Vec
+	}
+	type args struct {
+		d pixel.Circle
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Circle
+	}{
+		{
+			name:   "Circle.Intersect(): intersecting circles",
+			fields: fields{radius: 1, center: pixel.ZV},
+			args:   args{d: pixel.C(pixel.V(1, 0), 1)},
+			want:   pixel.C(pixel.V(0.5, 0), 1),
+		},
+		{
+			name:   "Circle.Intersect(): non-intersecting circles",
+			fields: fields{radius: 1, center: pixel.ZV},
+			args:   args{d: pixel.C(pixel.V(3, 3), 1)},
+			want:   pixel.C(pixel.V(1.5, 1.5), 0),
+		},
+		{
+			name:   "Circle.Intersect(): first circle encompassing second",
+			fields: fields{radius: 10, center: pixel.ZV},
+			args:   args{d: pixel.C(pixel.V(3, 3), 1)},
+			want:   pixel.C(pixel.ZV, 10),
+		},
+		{
+			name:   "Circle.Intersect(): second circle encompassing first",
+			fields: fields{radius: 1, center: pixel.V(-1, -4)},
+			args:   args{d: pixel.C(pixel.ZV, 10)},
+			want:   pixel.C(pixel.ZV, 10),
+		},
+		{
+			name:   "Circle.Intersect(): matching circles",
+			fields: fields{radius: 1, center: pixel.ZV},
+			args:   args{d: pixel.C(pixel.ZV, 1)},
+			want:   pixel.C(pixel.ZV, 1),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.C(
+				tt.fields.center,
+				tt.fields.radius,
+			)
+			if got := c.Intersect(tt.args.d); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Circle.Intersect() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestCircle_IntersectPoints(t *testing.T) {
+	type fields struct {
+		Center pixel.Vec
+		Radius float64
+	}
+	type args struct {
+		l pixel.Line
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   []pixel.Vec
+	}{
+		{
+			name:   "Line intersects circle at two points",
+			fields: fields{Center: pixel.V(2, 2), Radius: 1},
+			args:   args{pixel.L(pixel.V(0, 0), pixel.V(10, 10))},
+			want:   []pixel.Vec{pixel.V(1.292, 1.292), pixel.V(2.707, 2.707)},
+		},
+		{
+			name:   "Line intersects circle at one point",
+			fields: fields{Center: pixel.V(-0.5, -0.5), Radius: 1},
+			args:   args{pixel.L(pixel.V(0, 0), pixel.V(10, 10))},
+			want:   []pixel.Vec{pixel.V(0.207, 0.207)},
+		},
+		{
+			name:   "Line endpoint is circle center",
+			fields: fields{Center: pixel.V(0, 0), Radius: 1},
+			args:   args{pixel.L(pixel.V(0, 0), pixel.V(10, 10))},
+			want:   []pixel.Vec{pixel.V(0.707, 0.707)},
+		},
+		{
+			name:   "Both line endpoints within circle",
+			fields: fields{Center: pixel.V(0, 0), Radius: 1},
+			args:   args{pixel.L(pixel.V(0.2, 0.2), pixel.V(0.5, 0.5))},
+			want:   []pixel.Vec{},
+		},
+		{
+			name:   "Line does not intersect circle",
+			fields: fields{Center: pixel.V(10, 0), Radius: 1},
+			args:   args{pixel.L(pixel.V(0, 0), pixel.V(10, 10))},
+			want:   []pixel.Vec{},
+		},
+		{
+			name:   "Horizontal line intersects circle at two points",
+			fields: fields{Center: pixel.V(5, 5), Radius: 1},
+			args:   args{pixel.L(pixel.V(0, 5), pixel.V(10, 5))},
+			want:   []pixel.Vec{pixel.V(4, 5), pixel.V(6, 5)},
+		},
+		{
+			name:   "Vertical line intersects circle at two points",
+			fields: fields{Center: pixel.V(5, 5), Radius: 1},
+			args:   args{pixel.L(pixel.V(5, 0), pixel.V(5, 10))},
+			want:   []pixel.Vec{pixel.V(5, 4), pixel.V(5, 6)},
+		},
+		{
+			name:   "Left and down line intersects circle at two points",
+			fields: fields{Center: pixel.V(5, 5), Radius: 1},
+			args:   args{pixel.L(pixel.V(10, 10), pixel.V(0, 0))},
+			want:   []pixel.Vec{pixel.V(5.707, 5.707), pixel.V(4.292, 4.292)},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			c := pixel.Circle{
+				Center: tt.fields.Center,
+				Radius: tt.fields.Radius,
+			}
+			got := c.IntersectionPoints(tt.args.l)
+			for i, v := range got {
+				if !closeEnough(v.X, tt.want[i].X, 2) || !closeEnough(v.Y, tt.want[i].Y, 2) {
+					t.Errorf("Circle.IntersectPoints() = %v, want %v", v, tt.want[i])
+				}
+			}
+		})
+	}
+}

data.go

@@ -8,15 +8,15 @@ import (
 	"math"
 )
 
-var (
+// zeroValueTriangleData is the default value of a TriangleData element
-	// zeroValueTriangleData is the default value of a TriangleData element
+var zeroValueTriangleData = struct {
-	zeroValueTriangleData = struct {
+	Position  Vec
-		Position  Vec
+	Color     RGBA
-		Color     RGBA
+	Picture   Vec
-		Picture   Vec
+	Intensity float64
-		Intensity float64
+	ClipRect  Rect
-	}{Color: RGBA{1, 1, 1, 1}}
+	IsClipped bool
-)
+}{Color: RGBA{1, 1, 1, 1}}
 
 // TrianglesData specifies a list of Triangles vertices with three common properties:
 // TrianglesPosition, TrianglesColor and TrianglesPicture.
@@ -25,6 +25,8 @@ type TrianglesData []struct {
 	Color     RGBA
 	Picture   Vec
 	Intensity float64
+	ClipRect  Rect
+	IsClipped bool
 }
 
 // MakeTrianglesData creates TrianglesData of length len initialized with default property values.
@@ -89,6 +91,11 @@ func (td *TrianglesData) updateData(t Triangles) {
 			(*td)[i].Picture, (*td)[i].Intensity = t.Picture(i)
 		}
 	}
+	if t, ok := t.(TrianglesClipped); ok {
+		for i := range *td {
+			(*td)[i].ClipRect, (*td)[i].IsClipped = t.ClipRect(i)
+		}
+	}
 }
 
 // Update copies vertex properties from the supplied Triangles into this TrianglesData.
@@ -123,6 +130,11 @@ func (td *TrianglesData) Picture(i int) (pic Vec, intensity float64) {
 	return (*td)[i].Picture, (*td)[i].Intensity
 }
 
+// ClipRect returns the clipping rectangle property of the i-th vertex.
+func (td *TrianglesData) ClipRect(i int) (rect Rect, has bool) {
+	return (*td)[i].ClipRect, (*td)[i].IsClipped
+}
+
 // PictureData specifies an in-memory rectangular area of pixels and implements Picture and
 // PictureColor.
 //

data_test.go

@@ -266,3 +266,35 @@ func BenchmarkTrianglesData_Picture(b *testing.B) {
 		})
 	}
 }
+
+func BenchmarkTrianglesData_ClipRect(b *testing.B) {
+	tests := []struct {
+		name     string
+		tData    *pixel.TrianglesData
+		position int
+	}{
+		{
+			name:     "Getting beginning position",
+			tData:    pixel.MakeTrianglesData(1000),
+			position: 2,
+		},
+		{
+			name:     "Getting middle position",
+			tData:    pixel.MakeTrianglesData(1000),
+			position: 500,
+		},
+		{
+			name:     "Getting end position",
+			tData:    pixel.MakeTrianglesData(1000),
+			position: 999,
+		},
+	}
+
+	for _, tt := range tests {
+		b.Run(tt.name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				_, _ = tt.tData.ClipRect(tt.position)
+			}
+		})
+	}
+}

drawer.go

@@ -23,9 +23,11 @@ package pixel
 type Drawer struct {
 	Triangles Triangles
 	Picture   Picture
+	Cached    bool
 
-	targets map[Target]*drawerTarget
+	targets    map[Target]*drawerTarget
-	inited  bool
+	allTargets []*drawerTarget
+	inited     bool
 }
 
 type drawerTarget struct {
@@ -46,7 +48,7 @@ func (d *Drawer) lazyInit() {
 func (d *Drawer) Dirty() {
 	d.lazyInit()
 
-	for _, t := range d.targets {
+	for _, t := range d.allTargets {
 		t.clean = false
 	}
 }
@@ -68,6 +70,7 @@ func (d *Drawer) Draw(t Target) {
 			pics: make(map[Picture]TargetPicture),
 		}
 		d.targets[t] = dt
+		d.allTargets = append(d.allTargets, dt)
 	}
 
 	if dt.tris == nil {
@@ -89,7 +92,10 @@ func (d *Drawer) Draw(t Target) {
 	pic := dt.pics[d.Picture]
 	if pic == nil {
 		pic = t.MakePicture(d.Picture)
-		dt.pics[d.Picture] = pic
+
+		if d.Cached {
+			dt.pics[d.Picture] = pic
+		}
 	}
 
 	pic.Draw(dt.tris)

go.mod

@@ -3,13 +3,13 @@ module github.com/faiface/pixel
 go 1.12
 
 require (
-	github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380
+	github.com/faiface/glhf v0.0.0-20211013000516-57b20770c369
 	github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3
-	github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7 // indirect
+	github.com/go-gl/gl v0.0.0-20210905235341-f7a045908259
-	github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1
+	github.com/go-gl/glfw/v3.3/glfw v0.0.0-20210727001814-0db043d8d5be
-	github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7
+	github.com/go-gl/mathgl v1.0.0
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
-	github.com/pkg/errors v0.8.1
+	github.com/pkg/errors v0.9.1
-	github.com/stretchr/testify v1.3.0
+	github.com/stretchr/testify v1.7.0
-	golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff
+	golang.org/x/image v0.5.0
 )

go.sum

@@ -1,25 +1,54 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380 h1:FvZ0mIGh6b3kOITxUnxS3tLZMh7yEoHo75v3/AgUqg0=
+github.com/faiface/glhf v0.0.0-20211013000516-57b20770c369 h1:gv4BgP50atccdK/1tZHDyP6rMwiiutR2HPreR/OyLzI=
-github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380/go.mod h1:zqnPFFIuYFFxl7uH2gYByJwIVKG7fRqlqQCbzAnHs9g=
+github.com/faiface/glhf v0.0.0-20211013000516-57b20770c369/go.mod h1:dDdUO+G9ZnJ9sc8nIUvhLkE45k8PEKW6+A3TdWsfpV0=
 github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3 h1:baVdMKlASEHrj19iqjARrPbaRisD7EuZEVJj6ZMLl1Q=
 github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3/go.mod h1:VEPNJUlxl5KdWjDvz6Q1l+rJlxF2i6xqDeGuGAxa87M=
-github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7 h1:SCYMcCJ89LjRGwEa0tRluNRiMjZHalQZrVrvTbPh+qw=
+github.com/go-gl/gl v0.0.0-20210905235341-f7a045908259 h1:8q7+xl2D2qHPLTII1t4vSMNP2VKwDcn+Avf2WXvdB1A=
-github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7/go.mod h1:482civXOzJJCPzJ4ZOX/pwvXBWSnzD4OKMdH4ClKGbk=
+github.com/go-gl/gl v0.0.0-20210905235341-f7a045908259/go.mod h1:wjpnOv6ONl2SuJSxqCPVaPZibGFdSci9HFocT9qtVYM=
-github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1 h1:QbL/5oDUmRBzO9/Z7Seo6zf912W/a6Sr4Eu0G/3Jho0=
+github.com/go-gl/glfw v0.0.0-20210727001814-0db043d8d5be h1:UVW91pfMB1GRQfVwC7//RGVbqX6Ea8jURmJhlANak1M=
-github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
+github.com/go-gl/glfw v0.0.0-20210727001814-0db043d8d5be/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
-github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7 h1:THttjeRn1iiz69E875U6gAik8KTWk/JYAHoSVpUxBBI=
+github.com/go-gl/glfw/v3.3/glfw v0.0.0-20210727001814-0db043d8d5be h1:vEIVIuBApEBQTEJt19GfhoU+zFSV+sNTa9E9FdnRYfk=
-github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7/go.mod h1:yhpkQzEiH9yPyxDUGzkmgScbaBVlhC06qodikEM0ZwQ=
+github.com/go-gl/glfw/v3.3/glfw v0.0.0-20210727001814-0db043d8d5be/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
+github.com/go-gl/mathgl v1.0.0 h1:t9DznWJlXxxjeeKLIdovCOVJQk/GzDEL7h/h+Ro2B68=
+github.com/go-gl/mathgl v1.0.0/go.mod h1:yhpkQzEiH9yPyxDUGzkmgScbaBVlhC06qodikEM0ZwQ=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
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 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
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 golang.org/x/image v0.0.0-20190321063152-3fc05d484e9f/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
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 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
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+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

imdraw/imdraw.go

@@ -128,7 +128,9 @@ func (imd *IMDraw) Draw(t pixel.Target) {
 // Push adds some points to the IM queue. All Pushed points will have the same properties except for
 // the position.
 func (imd *IMDraw) Push(pts ...pixel.Vec) {
+	// Assert that Color is of type pixel.RGBA,
 	if _, ok := imd.Color.(pixel.RGBA); !ok {
+		// otherwise cast it
 		imd.Color = pixel.ToRGBA(imd.Color)
 	}
 	opts := point{

interface.go

@@ -92,7 +92,7 @@ type TrianglesColor interface {
 	Color(i int) RGBA
 }
 
-// TrianglesPicture specifies Triangles with Picture propery.
+// TrianglesPicture specifies Triangles with Picture property.
 //
 // The first value returned from Picture method is Picture coordinates. The second one specifies the
 // weight of the Picture. Value of 0 means, that Picture should be completely ignored, 1 means that
@@ -102,10 +102,19 @@ type TrianglesPicture interface {
 	Picture(i int) (pic Vec, intensity float64)
 }
 
+// TrianglesClipped specifies Triangles with Clipping Rectangle property.
+//
+// The first value returned from ClipRect method is the clipping rectangle. The second one specifies
+// if the triangle is clipped.
+type TrianglesClipped interface {
+	Triangles
+	ClipRect(i int) (rect Rect, is bool)
+}
+
 // Picture represents a rectangular area of raster data, such as a color. It has Bounds which
 // specify the rectangle where data is located.
 type Picture interface {
-	// Bounds returns the rectangle of the Picture. All data is located witih this rectangle.
+	// Bounds returns the rectangle of the Picture. All data is located within this rectangle.
 	// Querying properties outside the rectangle should return default value of that property.
 	Bounds() Rect
 }

line_test.go

@@ -0,0 +1,699 @@
+package pixel_test
+
+import (
+	"math"
+	"reflect"
+	"testing"
+
+	"github.com/faiface/pixel"
+)
+
+func TestLine_Bounds(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   pixel.Rect
+	}{
+		{
+			name:   "Positive slope",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			want:   pixel.R(0, 0, 10, 10),
+		},
+		{
+			name:   "Negative slope",
+			fields: fields{A: pixel.V(10, 10), B: pixel.V(0, 0)},
+			want:   pixel.R(0, 0, 10, 10),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.Bounds(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.Bounds() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Center(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   pixel.Vec
+	}{
+		{
+			name:   "Positive slope",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			want:   pixel.V(5, 5),
+		},
+		{
+			name:   "Negative slope",
+			fields: fields{A: pixel.V(10, 10), B: pixel.V(0, 0)},
+			want:   pixel.V(5, 5),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.Center(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.Center() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Closest(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		v pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Vec
+	}{
+		{
+			name:   "Point on line",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{v: pixel.V(5, 5)},
+			want:   pixel.V(5, 5),
+		},
+		{
+			name:   "Point on next to line",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{v: pixel.V(0, 10)},
+			want:   pixel.V(5, 5),
+		},
+		{
+			name:   "Point on next to vertical line",
+			fields: fields{A: pixel.V(5, 0), B: pixel.V(5, 10)},
+			args:   args{v: pixel.V(6, 5)},
+			want:   pixel.V(5, 5),
+		},
+		{
+			name:   "Point on next to horizontal line",
+			fields: fields{A: pixel.V(0, 5), B: pixel.V(10, 5)},
+			args:   args{v: pixel.V(5, 6)},
+			want:   pixel.V(5, 5),
+		},
+		{
+			name:   "Point far from line",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{v: pixel.V(80, -70)},
+			want:   pixel.V(5, 5),
+		},
+		{
+			name:   "Point on inline with line",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{v: pixel.V(20, 20)},
+			want:   pixel.V(10, 10),
+		},
+		{
+			name:   "Vertical line",
+			fields: fields{A: pixel.V(0, -10), B: pixel.V(0, 10)},
+			args:   args{v: pixel.V(-1, 0)},
+			want:   pixel.V(0, 0),
+		},
+		{
+			name:   "Horizontal line",
+			fields: fields{A: pixel.V(-10, 0), B: pixel.V(10, 0)},
+			args:   args{v: pixel.V(0, -1)},
+			want:   pixel.V(0, 0),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.Closest(tt.args.v); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.Closest() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Contains(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		v pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   bool
+	}{
+		{
+			name:   "Point on line",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{v: pixel.V(5, 5)},
+			want:   true,
+		},
+		{
+			name:   "Point on negative sloped line",
+			fields: fields{A: pixel.V(0, 10), B: pixel.V(10, 0)},
+			args:   args{v: pixel.V(5, 5)},
+			want:   true,
+		},
+		{
+			name:   "Point not on line",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{v: pixel.V(0, 10)},
+			want:   false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.Contains(tt.args.v); got != tt.want {
+				t.Errorf("Line.Contains() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Formula(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		wantM  float64
+		wantB  float64
+	}{
+		{
+			name:   "Getting formula - 45 degs",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			wantM:  1,
+			wantB:  0,
+		},
+		{
+			name:   "Getting formula - 90 degs",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(0, 10)},
+			wantM:  math.Inf(1),
+			wantB:  math.NaN(),
+		},
+		{
+			name:   "Getting formula - 0 degs",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 0)},
+			wantM:  0,
+			wantB:  0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			gotM, gotB := l.Formula()
+			if gotM != tt.wantM {
+				t.Errorf("Line.Formula() gotM = %v, want %v", gotM, tt.wantM)
+			}
+			if gotB != tt.wantB {
+				if math.IsNaN(tt.wantB) && !math.IsNaN(gotB) {
+					t.Errorf("Line.Formula() gotB = %v, want %v", gotB, tt.wantB)
+				}
+			}
+		})
+	}
+}
+
+func TestLine_Intersect(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		k pixel.Line
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Vec
+		want1  bool
+	}{
+		{
+			name:   "Lines intersect",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{k: pixel.L(pixel.V(0, 10), pixel.V(10, 0))},
+			want:   pixel.V(5, 5),
+			want1:  true,
+		},
+		{
+			name:   "Lines intersect 2",
+			fields: fields{A: pixel.V(5, 1), B: pixel.V(1, 1)},
+			args:   args{k: pixel.L(pixel.V(2, 0), pixel.V(2, 3))},
+			want:   pixel.V(2, 1),
+			want1:  true,
+		},
+		{
+			name:   "Line intersect with vertical",
+			fields: fields{A: pixel.V(5, 0), B: pixel.V(5, 10)},
+			args:   args{k: pixel.L(pixel.V(0, 0), pixel.V(10, 10))},
+			want:   pixel.V(5, 5),
+			want1:  true,
+		},
+		{
+			name:   "Line intersect with horizontal",
+			fields: fields{A: pixel.V(0, 5), B: pixel.V(10, 5)},
+			args:   args{k: pixel.L(pixel.V(0, 0), pixel.V(10, 10))},
+			want:   pixel.V(5, 5),
+			want1:  true,
+		},
+		{
+			name:   "Lines don't intersect",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{k: pixel.L(pixel.V(0, 10), pixel.V(1, 20))},
+			want:   pixel.ZV,
+			want1:  false,
+		},
+		{
+			name:   "Lines don't intersect 2",
+			fields: fields{A: pixel.V(1, 1), B: pixel.V(1, 5)},
+			args:   args{k: pixel.L(pixel.V(-5, 0), pixel.V(-2, 2))},
+			want:   pixel.ZV,
+			want1:  false,
+		},
+		{
+			name:   "Lines don't intersect 3",
+			fields: fields{A: pixel.V(2, 0), B: pixel.V(2, 3)},
+			args:   args{k: pixel.L(pixel.V(1, 5), pixel.V(5, 5))},
+			want:   pixel.ZV,
+			want1:  false,
+		},
+		{
+			name:   "Lines parallel",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{k: pixel.L(pixel.V(0, 1), pixel.V(10, 11))},
+			want:   pixel.ZV,
+			want1:  false,
+		}, {
+			name:   "Lines intersect",
+			fields: fields{A: pixel.V(600, 600), B: pixel.V(925, 150)},
+			args:   args{k: pixel.L(pixel.V(740, 255), pixel.V(925, 255))},
+			want:   pixel.V(849.1666666666666, 255),
+			want1:  true,
+		},
+		{
+			name:   "Lines intersect",
+			fields: fields{A: pixel.V(600, 600), B: pixel.V(925, 150)},
+			args:   args{k: pixel.L(pixel.V(740, 255), pixel.V(925, 255.0001))},
+			want:   pixel.V(849.1666240490657, 255.000059008986),
+			want1:  true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			got, got1 := l.Intersect(tt.args.k)
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.Intersect() got = %v, want %v", got, tt.want)
+			}
+			if got1 != tt.want1 {
+				t.Errorf("Line.Intersect() got1 = %v, want %v", got1, tt.want1)
+			}
+		})
+	}
+}
+
+func TestLine_IntersectCircle(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		c pixel.Circle
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Vec
+	}{
+		{
+			name:   "Cirle intersects",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(6, 4), 2)},
+			want:   pixel.V(0.5857864376269049, -0.5857864376269049),
+		},
+		{
+			name:   "Cirle doesn't intersects",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(0, 5), 1)},
+			want:   pixel.ZV,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.IntersectCircle(tt.args.c); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.IntersectCircle() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_IntersectRect(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		r pixel.Rect
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Vec
+	}{
+		{
+			name:   "Line through rect vertically",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(0, 10)},
+			args:   args{r: pixel.R(-1, 1, 5, 5)},
+			want:   pixel.V(-1, 0),
+		},
+		{
+			name:   "Line through rect horizontally",
+			fields: fields{A: pixel.V(0, 1), B: pixel.V(10, 1)},
+			args:   args{r: pixel.R(1, 0, 5, 5)},
+			want:   pixel.V(0, -1),
+		},
+		{
+			name:   "Line through rect diagonally bottom and left edges",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{r: pixel.R(0, 2, 3, 3)},
+			want:   pixel.V(-1, 1),
+		},
+		{
+			name:   "Line through rect diagonally top and right edges",
+			fields: fields{A: pixel.V(10, 0), B: pixel.V(0, 10)},
+			args:   args{r: pixel.R(5, 0, 8, 3)},
+			want:   pixel.V(-2.5, -2.5),
+		},
+		{
+			name:   "Line with not rect intersect",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{r: pixel.R(20, 20, 21, 21)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Line intersects at 0,0",
+			fields: fields{A: pixel.V(0, -10), B: pixel.V(0, 10)},
+			args:   args{r: pixel.R(-1, 0, 2, 2)},
+			want:   pixel.V(-1, 0),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.IntersectRect(tt.args.r); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.IntersectRect() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Len(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   float64
+	}{
+		{
+			name:   "End right-up of start",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(3, 4)},
+			want:   5,
+		},
+		{
+			name:   "End left-up of start",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(-3, 4)},
+			want:   5,
+		},
+		{
+			name:   "End right-down of start",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(3, -4)},
+			want:   5,
+		},
+		{
+			name:   "End left-down of start",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(-3, -4)},
+			want:   5,
+		},
+		{
+			name:   "End same as start",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(0, 0)},
+			want:   0,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.Len(); got != tt.want {
+				t.Errorf("Line.Len() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Rotated(t *testing.T) {
+	// round returns the nearest integer, rounding ties away from zero.
+	// This is required because `math.Round` wasn't introduced until Go1.10
+	round := func(x float64) float64 {
+		t := math.Trunc(x)
+		if math.Abs(x-t) >= 0.5 {
+			return t + math.Copysign(1, x)
+		}
+		return t
+	}
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		around pixel.Vec
+		angle  float64
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Line
+	}{
+		{
+			name:   "Rotating around line center",
+			fields: fields{A: pixel.V(1, 1), B: pixel.V(3, 3)},
+			args:   args{around: pixel.V(2, 2), angle: math.Pi},
+			want:   pixel.L(pixel.V(3, 3), pixel.V(1, 1)),
+		},
+		{
+			name:   "Rotating around x-y origin",
+			fields: fields{A: pixel.V(1, 1), B: pixel.V(3, 3)},
+			args:   args{around: pixel.V(0, 0), angle: math.Pi},
+			want:   pixel.L(pixel.V(-1, -1), pixel.V(-3, -3)),
+		},
+		{
+			name:   "Rotating around line end",
+			fields: fields{A: pixel.V(1, 1), B: pixel.V(3, 3)},
+			args:   args{around: pixel.V(1, 1), angle: math.Pi},
+			want:   pixel.L(pixel.V(1, 1), pixel.V(-1, -1)),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			// Have to round the results, due to floating-point in accuracies.  Results are correct to approximately
+			// 10 decimal places.
+			got := l.Rotated(tt.args.around, tt.args.angle)
+			if round(got.A.X) != tt.want.A.X ||
+				round(got.B.X) != tt.want.B.X ||
+				round(got.A.Y) != tt.want.A.Y ||
+				round(got.B.Y) != tt.want.B.Y {
+				t.Errorf("Line.Rotated() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_Scaled(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		scale float64
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Line
+	}{
+		{
+			name:   "Scaling by 1",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{scale: 1},
+			want:   pixel.L(pixel.V(0, 0), pixel.V(10, 10)),
+		},
+		{
+			name:   "Scaling by >1",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{scale: 2},
+			want:   pixel.L(pixel.V(-5, -5), pixel.V(15, 15)),
+		},
+		{
+			name:   "Scaling by <1",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{scale: 0.5},
+			want:   pixel.L(pixel.V(2.5, 2.5), pixel.V(7.5, 7.5)),
+		},
+		{
+			name:   "Scaling by -1",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{scale: -1},
+			want:   pixel.L(pixel.V(10, 10), pixel.V(0, 0)),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.Scaled(tt.args.scale); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.Scaled() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_ScaledXY(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	type args struct {
+		around pixel.Vec
+		scale  float64
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Line
+	}{
+		{
+			name:   "Scaling by 1 around origin",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{around: pixel.ZV, scale: 1},
+			want:   pixel.L(pixel.V(0, 0), pixel.V(10, 10)),
+		},
+		{
+			name:   "Scaling by >1 around origin",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{around: pixel.ZV, scale: 2},
+			want:   pixel.L(pixel.V(0, 0), pixel.V(20, 20)),
+		},
+		{
+			name:   "Scaling by <1 around origin",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{around: pixel.ZV, scale: 0.5},
+			want:   pixel.L(pixel.V(0, 0), pixel.V(5, 5)),
+		},
+		{
+			name:   "Scaling by -1 around origin",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(10, 10)},
+			args:   args{around: pixel.ZV, scale: -1},
+			want:   pixel.L(pixel.V(0, 0), pixel.V(-10, -10)),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.ScaledXY(tt.args.around, tt.args.scale); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Line.ScaledXY() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestLine_String(t *testing.T) {
+	type fields struct {
+		A pixel.Vec
+		B pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   string
+	}{
+		{
+			name:   "Getting string",
+			fields: fields{A: pixel.V(0, 0), B: pixel.V(1, 1)},
+			want:   "Line(Vec(0, 0), Vec(1, 1))",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			l := pixel.Line{
+				A: tt.fields.A,
+				B: tt.fields.B,
+			}
+			if got := l.String(); got != tt.want {
+				t.Errorf("Line.String() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

math.go

@@ -0,0 +1,15 @@
+package pixel
+
+// Clamp returns x clamped to the interval [min, max].
+//
+// If x is less than min, min is returned. If x is more than max, max is returned. Otherwise, x is
+// returned.
+func Clamp(x, min, max float64) float64 {
+	if x < min {
+		return min
+	}
+	if x > max {
+		return max
+	}
+	return x
+}

math_test.go

@@ -0,0 +1,46 @@
+package pixel_test
+
+import (
+	"fmt"
+	"math"
+	"testing"
+
+	"github.com/faiface/pixel"
+)
+
+// closeEnough will shift the decimal point by the accuracy required, truncates the results and compares them.
+// Effectively this compares two floats to a given decimal point.
+//  Example:
+//  closeEnough(100.125342432, 100.125, 2) == true
+//  closeEnough(math.Pi, 3.14, 2) == true
+//  closeEnough(0.1234, 0.1245, 3) == false
+func closeEnough(got, expected float64, decimalAccuracy int) bool {
+	gotShifted := got * math.Pow10(decimalAccuracy)
+	expectedShifted := expected * math.Pow10(decimalAccuracy)
+
+	return math.Trunc(gotShifted) == math.Trunc(expectedShifted)
+}
+
+type clampTest struct {
+	number   float64
+	min      float64
+	max      float64
+	expected float64
+}
+
+func TestClamp(t *testing.T) {
+	tests := []clampTest{
+		{number: 1, min: 0, max: 5, expected: 1},
+		{number: 2, min: 0, max: 5, expected: 2},
+		{number: 8, min: 0, max: 5, expected: 5},
+		{number: -5, min: 0, max: 5, expected: 0},
+		{number: -5, min: -4, max: 5, expected: -4},
+	}
+
+	for _, tc := range tests {
+		result := pixel.Clamp(tc.number, tc.min, tc.max)
+		if result != tc.expected {
+			t.Error(fmt.Sprintf("Clamping %v with min %v and max %v should have given %v, but gave %v", tc.number, tc.min, tc.max, tc.expected, result))
+		}
+	}
+}

matrix.go

@@ -0,0 +1,98 @@
+package pixel
+
+import (
+	"fmt"
+	"math"
+)
+
+// Matrix is a 2x3 affine matrix that can be used for all kinds of spatial transforms, such
+// as movement, scaling and rotations.
+//
+// Matrix has a handful of useful methods, each of which adds a transformation to the matrix. For
+// example:
+//
+//   pixel.IM.Moved(pixel.V(100, 200)).Rotated(pixel.ZV, math.Pi/2)
+//
+// This code creates a Matrix that first moves everything by 100 units horizontally and 200 units
+// vertically and then rotates everything by 90 degrees around the origin.
+//
+// Layout is:
+// [0] [2] [4]
+// [1] [3] [5]
+//  0   0   1  (implicit row)
+type Matrix [6]float64
+
+// IM stands for identity matrix. Does nothing, no transformation.
+var IM = Matrix{1, 0, 0, 1, 0, 0}
+
+// String returns a string representation of the Matrix.
+//
+//   m := pixel.IM
+//   fmt.Println(m) // Matrix(1 0 0 | 0 1 0)
+func (m Matrix) String() string {
+	return fmt.Sprintf(
+		"Matrix(%v %v %v | %v %v %v)",
+		m[0], m[2], m[4],
+		m[1], m[3], m[5],
+	)
+}
+
+// Moved moves everything by the delta vector.
+func (m Matrix) Moved(delta Vec) Matrix {
+	m[4], m[5] = m[4]+delta.X, m[5]+delta.Y
+	return m
+}
+
+// ScaledXY scales everything around a given point by the scale factor in each axis respectively.
+func (m Matrix) ScaledXY(around Vec, scale Vec) Matrix {
+	m[4], m[5] = m[4]-around.X, m[5]-around.Y
+	m[0], m[2], m[4] = m[0]*scale.X, m[2]*scale.X, m[4]*scale.X
+	m[1], m[3], m[5] = m[1]*scale.Y, m[3]*scale.Y, m[5]*scale.Y
+	m[4], m[5] = m[4]+around.X, m[5]+around.Y
+	return m
+}
+
+// Scaled scales everything around a given point by the scale factor.
+func (m Matrix) Scaled(around Vec, scale float64) Matrix {
+	return m.ScaledXY(around, V(scale, scale))
+}
+
+// Rotated rotates everything around a given point by the given angle in radians.
+func (m Matrix) Rotated(around Vec, angle float64) Matrix {
+	sint, cost := math.Sincos(angle)
+	m[4], m[5] = m[4]-around.X, m[5]-around.Y
+	m = m.Chained(Matrix{cost, sint, -sint, cost, 0, 0})
+	m[4], m[5] = m[4]+around.X, m[5]+around.Y
+	return m
+}
+
+// Chained adds another Matrix to this one. All tranformations by the next Matrix will be applied
+// after the transformations of this Matrix.
+func (m Matrix) Chained(next Matrix) Matrix {
+	return Matrix{
+		next[0]*m[0] + next[2]*m[1],
+		next[1]*m[0] + next[3]*m[1],
+		next[0]*m[2] + next[2]*m[3],
+		next[1]*m[2] + next[3]*m[3],
+		next[0]*m[4] + next[2]*m[5] + next[4],
+		next[1]*m[4] + next[3]*m[5] + next[5],
+	}
+}
+
+// Project applies all transformations added to the Matrix to a vector u and returns the result.
+//
+// Time complexity is O(1).
+func (m Matrix) Project(u Vec) Vec {
+	return Vec{m[0]*u.X + m[2]*u.Y + m[4], m[1]*u.X + m[3]*u.Y + m[5]}
+}
+
+// Unproject does the inverse operation to Project.
+//
+// Time complexity is O(1).
+func (m Matrix) Unproject(u Vec) Vec {
+	det := m[0]*m[3] - m[2]*m[1]
+	return Vec{
+		(m[3]*(u.X-m[4]) - m[2]*(u.Y-m[5])) / det,
+		(-m[1]*(u.X-m[4]) + m[0]*(u.Y-m[5])) / det,
+	}
+}

matrix_test.go

@@ -1,10 +1,13 @@
 package pixel_test
 
 import (
+	"fmt"
+	"math"
 	"math/rand"
 	"testing"
 
 	"github.com/faiface/pixel"
+	"github.com/stretchr/testify/assert"
 )
 
 func BenchmarkMatrix(b *testing.B) {
@@ -61,3 +64,86 @@ func BenchmarkMatrix(b *testing.B) {
 		}
 	})
 }
+
+func TestMatrix_Unproject(t *testing.T) {
+	const delta = 1e-15
+	t.Run("for rotated matrix", func(t *testing.T) {
+		matrix := pixel.IM.
+			Rotated(pixel.ZV, math.Pi/2)
+		unprojected := matrix.Unproject(pixel.V(0, 1))
+		assert.InDelta(t, unprojected.X, 1, delta)
+		assert.InDelta(t, unprojected.Y, 0, delta)
+	})
+	t.Run("for moved matrix", func(t *testing.T) {
+		matrix := pixel.IM.
+			Moved(pixel.V(1, 2))
+		unprojected := matrix.Unproject(pixel.V(2, 5))
+		assert.InDelta(t, unprojected.X, 1, delta)
+		assert.InDelta(t, unprojected.Y, 3, delta)
+	})
+	t.Run("for scaled matrix", func(t *testing.T) {
+		matrix := pixel.IM.
+			Scaled(pixel.ZV, 2)
+		unprojected := matrix.Unproject(pixel.V(2, 4))
+		assert.InDelta(t, unprojected.X, 1, delta)
+		assert.InDelta(t, unprojected.Y, 2, delta)
+	})
+	t.Run("for scaled, rotated and moved matrix", func(t *testing.T) {
+		matrix := pixel.IM.
+			Scaled(pixel.ZV, 2).
+			Rotated(pixel.ZV, math.Pi/2).
+			Moved(pixel.V(2, 2))
+		unprojected := matrix.Unproject(pixel.V(-2, 6))
+		assert.InDelta(t, unprojected.X, 2, delta)
+		assert.InDelta(t, unprojected.Y, 2, delta)
+	})
+	t.Run("for rotated and moved matrix", func(t *testing.T) {
+		matrix := pixel.IM.
+			Rotated(pixel.ZV, math.Pi/2).
+			Moved(pixel.V(1, 1))
+		unprojected := matrix.Unproject(pixel.V(1, 2))
+		assert.InDelta(t, unprojected.X, 1, delta)
+		assert.InDelta(t, unprojected.Y, 0, delta)
+	})
+	t.Run("for projected vertices using all kinds of matrices", func(t *testing.T) {
+		namedMatrices := map[string]pixel.Matrix{
+			"IM":                        pixel.IM,
+			"Scaled":                    pixel.IM.Scaled(pixel.ZV, 0.5),
+			"Scaled x 2":                pixel.IM.Scaled(pixel.ZV, 2),
+			"Rotated":                   pixel.IM.Rotated(pixel.ZV, math.Pi/4),
+			"Moved":                     pixel.IM.Moved(pixel.V(0.5, 1)),
+			"Moved 2":                   pixel.IM.Moved(pixel.V(-1, -0.5)),
+			"Scaled and Rotated":        pixel.IM.Scaled(pixel.ZV, 0.5).Rotated(pixel.ZV, math.Pi/4),
+			"Scaled, Rotated and Moved": pixel.IM.Scaled(pixel.ZV, 0.5).Rotated(pixel.ZV, math.Pi/4).Moved(pixel.V(1, 2)),
+			"Rotated and Moved":         pixel.IM.Rotated(pixel.ZV, math.Pi/4).Moved(pixel.V(1, 2)),
+		}
+		vertices := [...]pixel.Vec{
+			pixel.V(0, 0),
+			pixel.V(5, 0),
+			pixel.V(5, 10),
+			pixel.V(0, 10),
+			pixel.V(-5, 10),
+			pixel.V(-5, 0),
+			pixel.V(-5, -10),
+			pixel.V(0, -10),
+			pixel.V(5, -10),
+		}
+		for matrixName, matrix := range namedMatrices {
+			for _, vertex := range vertices {
+				testCase := fmt.Sprintf("for matrix %s and vertex %v", matrixName, vertex)
+				t.Run(testCase, func(t *testing.T) {
+					projected := matrix.Project(vertex)
+					unprojected := matrix.Unproject(projected)
+					assert.InDelta(t, vertex.X, unprojected.X, delta)
+					assert.InDelta(t, vertex.Y, unprojected.Y, delta)
+				})
+			}
+		}
+	})
+	t.Run("for singular matrix", func(t *testing.T) {
+		matrix := pixel.Matrix{0, 0, 0, 0, 0, 0}
+		unprojected := matrix.Unproject(pixel.ZV)
+		assert.True(t, math.IsNaN(unprojected.X))
+		assert.True(t, math.IsNaN(unprojected.Y))
+	})
+}

pixel_test.go

@@ -12,31 +12,31 @@ import (
 	"github.com/faiface/pixel/pixelgl"
 )
 
-var (
+// onePixelImage is the byte representation of a 1x1 solid white png file
-	// onePixelImage is the byte representation of a 1x1 solid white png file
+var onePixelImage = []byte{
-	onePixelImage = []byte{137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 1, 0, 0, 0, 1, 8, 2,
+	137, 80, 78, 71, 13, 10, 26, 10, 0, 0, 0, 13, 73, 72, 68, 82, 0, 0, 0, 1, 0, 0, 0, 1, 8, 2,
-		0, 0, 0, 144, 119, 83, 222, 0, 0, 1, 130, 105, 67, 67, 80, 73, 67, 67, 32, 112, 114, 111, 102, 105, 108, 101, 0,
+	0, 0, 0, 144, 119, 83, 222, 0, 0, 1, 130, 105, 67, 67, 80, 73, 67, 67, 32, 112, 114, 111, 102, 105, 108, 101, 0,
-		0, 40, 145, 125, 145, 59, 72, 3, 65, 20, 69, 143, 73, 68, 17, 37, 133, 41, 68, 44, 182, 80, 43, 5, 81, 17, 75,
+	0, 40, 145, 125, 145, 59, 72, 3, 65, 20, 69, 143, 73, 68, 17, 37, 133, 41, 68, 44, 182, 80, 43, 5, 81, 17, 75,
-		141, 66, 16, 34, 132, 168, 96, 212, 194, 221, 141, 137, 66, 118, 13, 187, 9, 54, 150, 130, 109, 192, 194, 79,
+	141, 66, 16, 34, 132, 168, 96, 212, 194, 221, 141, 137, 66, 118, 13, 187, 9, 54, 150, 130, 109, 192, 194, 79,
-		227, 175, 176, 177, 214, 214, 194, 86, 16, 4, 63, 32, 54, 182, 86, 138, 54, 18, 214, 55, 73, 32, 65, 140, 3,
+	227, 175, 176, 177, 214, 214, 194, 86, 16, 4, 63, 32, 54, 182, 86, 138, 54, 18, 214, 55, 73, 32, 65, 140, 3,
-		195, 28, 238, 188, 123, 121, 243, 6, 124, 71, 25, 211, 114, 3, 3, 96, 217, 57, 39, 30, 9, 107, 243, 137, 5, 173,
+	195, 28, 238, 188, 123, 121, 243, 6, 124, 71, 25, 211, 114, 3, 3, 96, 217, 57, 39, 30, 9, 107, 243, 137, 5, 173,
-		233, 149, 0, 65, 90, 104, 0, 221, 116, 179, 227, 177, 88, 148, 186, 235, 235, 94, 213, 193, 93, 191, 202, 170,
+	233, 149, 0, 65, 90, 104, 0, 221, 116, 179, 227, 177, 88, 148, 186, 235, 235, 94, 213, 193, 93, 191, 202, 170,
-		95, 247, 231, 106, 75, 174, 184, 38, 52, 104, 194, 99, 102, 214, 201, 9, 47, 11, 143, 108, 228, 178, 138, 247,
+	95, 247, 231, 106, 75, 174, 184, 38, 52, 104, 194, 99, 102, 214, 201, 9, 47, 11, 143, 108, 228, 178, 138, 247,
-		132, 67, 230, 170, 158, 20, 62, 23, 238, 115, 164, 65, 225, 71, 165, 27, 101, 126, 83, 156, 46, 177, 79, 101,
+	132, 67, 230, 170, 158, 20, 62, 23, 238, 115, 164, 65, 225, 71, 165, 27, 101, 126, 83, 156, 46, 177, 79, 101,
-		134, 156, 217, 248, 132, 112, 72, 88, 75, 215, 176, 81, 195, 230, 170, 99, 9, 15, 11, 119, 39, 45, 91, 242, 125,
+	134, 156, 217, 248, 132, 112, 72, 88, 75, 215, 176, 81, 195, 230, 170, 99, 9, 15, 11, 119, 39, 45, 91, 242, 125,
-		243, 101, 78, 42, 222, 84, 108, 101, 242, 102, 165, 79, 245, 194, 214, 21, 123, 110, 70, 233, 178, 187, 136, 48,
+	243, 101, 78, 42, 222, 84, 108, 101, 242, 102, 165, 79, 245, 194, 214, 21, 123, 110, 70, 233, 178, 187, 136, 48,
-		197, 52, 49, 52, 12, 242, 172, 145, 33, 71, 191, 156, 182, 40, 46, 113, 185, 15, 215, 241, 119, 150, 252, 49,
+	197, 52, 49, 52, 12, 242, 172, 145, 33, 71, 191, 156, 182, 40, 46, 113, 185, 15, 215, 241, 119, 150, 252, 49,
-		113, 25, 226, 90, 195, 20, 199, 36, 235, 88, 232, 37, 63, 234, 15, 126, 207, 214, 77, 13, 13, 150, 147, 90, 195,
+	113, 25, 226, 90, 195, 20, 199, 36, 235, 88, 232, 37, 63, 234, 15, 126, 207, 214, 77, 13, 13, 150, 147, 90, 195,
-		208, 248, 226, 121, 31, 61, 208, 180, 3, 197, 130, 231, 125, 31, 123, 94, 241, 4, 252, 207, 112, 101, 87, 253,
+	208, 248, 226, 121, 31, 61, 208, 180, 3, 197, 130, 231, 125, 31, 123, 94, 241, 4, 252, 207, 112, 101, 87, 253,
-		235, 71, 48, 250, 41, 122, 161, 170, 117, 31, 66, 112, 11, 46, 174, 171, 154, 177, 11, 151, 219, 208, 241, 148,
+	235, 71, 48, 250, 41, 122, 161, 170, 117, 31, 66, 112, 11, 46, 174, 171, 154, 177, 11, 151, 219, 208, 241, 148,
-		213, 29, 189, 36, 249, 101, 251, 82, 41, 120, 63, 147, 111, 74, 64, 251, 45, 180, 44, 150, 231, 86, 185, 231,
+	213, 29, 189, 36, 249, 101, 251, 82, 41, 120, 63, 147, 111, 74, 64, 251, 45, 180, 44, 150, 231, 86, 185, 231,
-		244, 1, 102, 101, 86, 209, 27, 216, 63, 128, 222, 180, 100, 47, 213, 121, 119, 115, 237, 220, 254, 173, 169,
+	244, 1, 102, 101, 86, 209, 27, 216, 63, 128, 222, 180, 100, 47, 213, 121, 119, 115, 237, 220, 254, 173, 169,
-		204, 239, 7, 178, 211, 114, 90, 10, 150, 157, 65, 0, 0, 0, 9, 112, 72, 89, 115, 0, 0, 46, 35, 0, 0, 46, 35, 1,
+	204, 239, 7, 178, 211, 114, 90, 10, 150, 157, 65, 0, 0, 0, 9, 112, 72, 89, 115, 0, 0, 46, 35, 0, 0, 46, 35, 1,
-		120, 165, 63, 118, 0, 0, 0, 7, 116, 73, 77, 69, 7, 227, 4, 15, 10, 5, 36, 189, 4, 224, 88, 0, 0, 0, 25, 116, 69,
+	120, 165, 63, 118, 0, 0, 0, 7, 116, 73, 77, 69, 7, 227, 4, 15, 10, 5, 36, 189, 4, 224, 88, 0, 0, 0, 25, 116, 69,
-		88, 116, 67, 111, 109, 109, 101, 110, 116, 0, 67, 114, 101, 97, 116, 101, 100, 32, 119, 105, 116, 104, 32, 71,
+	88, 116, 67, 111, 109, 109, 101, 110, 116, 0, 67, 114, 101, 97, 116, 101, 100, 32, 119, 105, 116, 104, 32, 71,
-		73, 77, 80, 87, 129, 14, 23, 0, 0, 0, 12, 73, 68, 65, 84, 8, 215, 99, 120, 241, 226, 61, 0, 5, 123, 2, 192, 194,
+	73, 77, 80, 87, 129, 14, 23, 0, 0, 0, 12, 73, 68, 65, 84, 8, 215, 99, 120, 241, 226, 61, 0, 5, 123, 2, 192, 194,
-		77, 211, 95, 0, 0, 0, 0, 73, 69, 78, 68, 174, 66, 96, 130}
+	77, 211, 95, 0, 0, 0, 0, 73, 69, 78, 68, 174, 66, 96, 130,
-)
+}
 
 func TestMain(m *testing.M) {
 	pixelgl.Run(func() {
@@ -54,8 +54,9 @@ func TestSprite_Draw(t *testing.T) {
 	sprite := pixel.NewSprite(pic, pic.Bounds())
 
 	cfg := pixelgl.WindowConfig{
-		Title:  "testing",
+		Title:     "testing",
-		Bounds: pixel.R(0, 0, 150, 150),
+		Bounds:    pixel.R(0, 0, 150, 150),
+		Invisible: true,
 	}
 
 	win, err := pixelgl.NewWindow(cfg)

pixelgl/canvas.go

@@ -17,7 +17,7 @@ import (
 // It supports TrianglesPosition, TrianglesColor, TrianglesPicture and PictureColor.
 type Canvas struct {
 	gf     *GLFrame
-	shader *glShader
+	shader *GLShader
 
 	cmp    pixel.ComposeMethod
 	mat    mgl32.Mat3
@@ -37,9 +37,8 @@ func NewCanvas(bounds pixel.Rect) *Canvas {
 		col: mgl32.Vec4{1, 1, 1, 1},
 	}
 
-	baseShader(c)
+	c.shader = NewGLShader(baseCanvasFragmentShader)
 	c.SetBounds(bounds)
-	c.shader.update()
 	return c
 }
 
@@ -47,22 +46,28 @@ func NewCanvas(bounds pixel.Rect) *Canvas {
 // attribute variable. If the uniform already exists, including defaults, they will be reassigned
 // to the new value. The value can be a pointer.
 func (c *Canvas) SetUniform(name string, value interface{}) {
-	c.shader.setUniform(name, value)
+	c.shader.SetUniform(name, value)
 }
 
 // SetFragmentShader allows you to set a new fragment shader on the underlying
 // framebuffer. Argument "src" is the GLSL source, not a filename.
 func (c *Canvas) SetFragmentShader(src string) {
 	c.shader.fs = src
-	c.shader.update()
+	c.shader.Update()
 }
 
 // MakeTriangles creates a specialized copy of the supplied Triangles that draws onto this Canvas.
 //
 // TrianglesPosition, TrianglesColor and TrianglesPicture are supported.
 func (c *Canvas) MakeTriangles(t pixel.Triangles) pixel.TargetTriangles {
+	if gt, ok := t.(*GLTriangles); ok {
+		return &canvasTriangles{
+			GLTriangles: gt,
+			dst:         c,
+		}
+	}
 	return &canvasTriangles{
-		GLTriangles: NewGLTriangles(c.shader.s, t),
+		GLTriangles: NewGLTriangles(c.shader, t),
 		dst:         c,
 	}
 }
@@ -128,7 +133,7 @@ func (c *Canvas) SetBounds(bounds pixel.Rect) {
 		c.sprite = pixel.NewSprite(nil, pixel.Rect{})
 	}
 	c.sprite.Set(c, c.Bounds())
-	//c.sprite.SetMatrix(pixel.IM.Moved(c.Bounds().Center()))
+	// c.sprite.SetMatrix(pixel.IM.Moved(c.Bounds().Center()))
 }
 
 // Bounds returns the rectangular bounds of the Canvas.
@@ -288,15 +293,15 @@ func (ct *canvasTriangles) draw(tex *glhf.Texture, bounds pixel.Rect) {
 		setBlendFunc(cmp)
 
 		frame := ct.dst.gf.Frame()
-		shader := ct.dst.shader.s
+		shader := ct.shader.s
 
 		frame.Begin()
 		shader.Begin()
 
-		ct.dst.shader.uniformDefaults.transform = mat
+		ct.shader.uniformDefaults.transform = mat
-		ct.dst.shader.uniformDefaults.colormask = col
+		ct.shader.uniformDefaults.colormask = col
 		dstBounds := ct.dst.Bounds()
-		ct.dst.shader.uniformDefaults.bounds = mgl32.Vec4{
+		ct.shader.uniformDefaults.bounds = mgl32.Vec4{
 			float32(dstBounds.Min.X),
 			float32(dstBounds.Min.Y),
 			float32(dstBounds.W()),
@@ -304,15 +309,15 @@ func (ct *canvasTriangles) draw(tex *glhf.Texture, bounds pixel.Rect) {
 		}
 
 		bx, by, bw, bh := intBounds(bounds)
-		ct.dst.shader.uniformDefaults.texbounds = mgl32.Vec4{
+		ct.shader.uniformDefaults.texbounds = mgl32.Vec4{
 			float32(bx),
 			float32(by),
 			float32(bw),
 			float32(bh),
 		}
 
-		for loc, u := range ct.dst.shader.uniforms {
+		for loc, u := range ct.shader.uniforms {
-			ct.dst.shader.s.SetUniformAttr(loc, u.Value())
+			ct.shader.s.SetUniformAttr(loc, u.Value())
 		}
 
 		if tex == nil {
@@ -354,17 +359,3 @@ func (cp *canvasPicture) Draw(t pixel.TargetTriangles) {
 	}
 	ct.draw(cp.GLPicture.Texture(), cp.GLPicture.Bounds())
 }
-
-const (
-	canvasPosition int = iota
-	canvasColor
-	canvasTexCoords
-	canvasIntensity
-)
-
-var defaultCanvasVertexFormat = glhf.AttrFormat{
-	canvasPosition:  {Name: "aPosition", Type: glhf.Vec2},
-	canvasColor:     {Name: "aColor", Type: glhf.Vec4},
-	canvasTexCoords: {Name: "aTexCoords", Type: glhf.Vec2},
-	canvasIntensity: {Name: "aIntensity", Type: glhf.Float},
-}

pixelgl/glshader.go

@@ -7,10 +7,10 @@ import (
 	"github.com/pkg/errors"
 )
 
-// glShader is a type to assist with managing a canvas's underlying
+// GLShader is a type to assist with managing a canvas's underlying
 // shader configuration. This allows for customization of shaders on
 // a per canvas basis.
-type glShader struct {
+type GLShader struct {
 	s      *glhf.Shader
 	vf, uf glhf.AttrFormat
 	vs, fs string
@@ -22,6 +22,7 @@ type glShader struct {
 		colormask mgl32.Vec4
 		bounds    mgl32.Vec4
 		texbounds mgl32.Vec4
+		cliprect  mgl32.Vec4
 	}
 }
 
@@ -32,15 +33,52 @@ type gsUniformAttr struct {
 	ispointer bool
 }
 
-// reinitialize GLShader data and recompile the underlying gl shader object
+const (
-func (gs *glShader) update() {
+	canvasPosition int = iota
-	gs.uf = nil
+	canvasColor
-	for _, u := range gs.uniforms {
+	canvasTexCoords
-		gs.uf = append(gs.uf, glhf.Attr{
+	canvasIntensity
-			Name: u.Name,
+	canvasClip
-			Type: u.Type,
+)
-		})
+
+var defaultCanvasVertexFormat = glhf.AttrFormat{
+	canvasPosition:  glhf.Attr{Name: "aPosition", Type: glhf.Vec2},
+	canvasColor:     glhf.Attr{Name: "aColor", Type: glhf.Vec4},
+	canvasTexCoords: glhf.Attr{Name: "aTexCoords", Type: glhf.Vec2},
+	canvasIntensity: glhf.Attr{Name: "aIntensity", Type: glhf.Float},
+  canvasClip:      glhf.Attr{Name: "aClipRect", Type: glhf.Vec4},
+}
+
+// Sets up a base shader with everything needed for a Pixel
+// canvas to render correctly. The defaults can be overridden
+// by simply using the SetUniform function.
+func NewGLShader(fragmentShader string) *GLShader {
+	gs := &GLShader{
+		vf: defaultCanvasVertexFormat,
+		vs: baseCanvasVertexShader,
+		fs: fragmentShader,
 	}
+
+	gs.SetUniform("uTransform", &gs.uniformDefaults.transform)
+	gs.SetUniform("uColorMask", &gs.uniformDefaults.colormask)
+	gs.SetUniform("uBounds", &gs.uniformDefaults.bounds)
+	gs.SetUniform("uTexBounds", &gs.uniformDefaults.texbounds)
+
+	gs.Update()
+
+	return gs
+}
+
+// Update reinitialize GLShader data and recompile the underlying gl shader object
+func (gs *GLShader) Update() {
+	gs.uf = make([]glhf.Attr, len(gs.uniforms))
+	for idx := range gs.uniforms {
+		gs.uf[idx] = glhf.Attr{
+			Name: gs.uniforms[idx].Name,
+			Type: gs.uniforms[idx].Type,
+		}
+	}
+
 	var shader *glhf.Shader
 	mainthread.Call(func() {
 		var err error
@@ -59,7 +97,7 @@ func (gs *glShader) update() {
 }
 
 // gets the uniform index from GLShader
-func (gs *glShader) getUniform(Name string) int {
+func (gs *GLShader) getUniform(Name string) int {
 	for i, u := range gs.uniforms {
 		if u.Name == Name {
 			return i
@@ -75,7 +113,7 @@ func (gs *glShader) getUniform(Name string) int {
 //
 //   utime := float32(time.Since(starttime)).Seconds())
 //   mycanvas.shader.AddUniform("u_time", &utime)
-func (gs *glShader) setUniform(name string, value interface{}) {
+func (gs *GLShader) SetUniform(name string, value interface{}) {
 	t, p := getAttrType(value)
 	if loc := gs.getUniform(name); loc > -1 {
 		gs.uniforms[loc].Name = name
@@ -92,24 +130,6 @@ func (gs *glShader) setUniform(name string, value interface{}) {
 	})
 }
 
-// Sets up a base shader with everything needed for a Pixel
-// canvas to render correctly. The defaults can be overridden
-// by simply using the SetUniform function.
-func baseShader(c *Canvas) {
-	gs := &glShader{
-		vf: defaultCanvasVertexFormat,
-		vs: baseCanvasVertexShader,
-		fs: baseCanvasFragmentShader,
-	}
-
-	gs.setUniform("uTransform", &gs.uniformDefaults.transform)
-	gs.setUniform("uColorMask", &gs.uniformDefaults.colormask)
-	gs.setUniform("uBounds", &gs.uniformDefaults.bounds)
-	gs.setUniform("uTexBounds", &gs.uniformDefaults.texbounds)
-
-	c.shader = gs
-}
-
 // Value returns the attribute's concrete value. If the stored value
 // is a pointer, we return the dereferenced value.
 func (gu *gsUniformAttr) Value() interface{} {
@@ -222,11 +242,14 @@ in vec2  aPosition;
 in vec4  aColor;
 in vec2  aTexCoords;
 in float aIntensity;
+in vec4  aClipRect;
+in float aIsClipped;
 
 out vec4  vColor;
 out vec2  vTexCoords;
 out float vIntensity;
 out vec2  vPosition;
+out vec4  vClipRect;
 
 uniform mat3 uTransform;
 uniform vec4 uBounds;
@@ -235,10 +258,12 @@ void main() {
 	vec2 transPos = (uTransform * vec3(aPosition, 1.0)).xy;
 	vec2 normPos = (transPos - uBounds.xy) / uBounds.zw * 2 - vec2(1, 1);
 	gl_Position = vec4(normPos, 0.0, 1.0);
+
 	vColor = aColor;
 	vPosition = aPosition;
 	vTexCoords = aTexCoords;
 	vIntensity = aIntensity;
+	vClipRect = aClipRect;
 }
 `
 
@@ -248,6 +273,7 @@ var baseCanvasFragmentShader = `
 in vec4  vColor;
 in vec2  vTexCoords;
 in float vIntensity;
+in vec4  vClipRect;
 
 out vec4 fragColor;
 
@@ -256,6 +282,9 @@ uniform vec4 uTexBounds;
 uniform sampler2D uTexture;
 
 void main() {
+	if ((vClipRect != vec4(0,0,0,0)) && (gl_FragCoord.x < vClipRect.x || gl_FragCoord.y < vClipRect.y || gl_FragCoord.x > vClipRect.z || gl_FragCoord.y > vClipRect.w))
+		discard;
+
 	if (vIntensity == 0) {
 		fragColor = uColorMask * vColor;
 	} else {

pixelgl/gltriangles.go

@@ -15,23 +15,43 @@ import (
 type GLTriangles struct {
 	vs     *glhf.VertexSlice
 	data   []float32
-	shader *glhf.Shader
+	shader *GLShader
 }
 
 var (
 	_ pixel.TrianglesPosition = (*GLTriangles)(nil)
 	_ pixel.TrianglesColor    = (*GLTriangles)(nil)
 	_ pixel.TrianglesPicture  = (*GLTriangles)(nil)
+	_ pixel.TrianglesClipped  = (*GLTriangles)(nil)
+)
+
+// The following is a helper so that the indices of
+// 	each of these items is easier to see/debug.
+const (
+	triPosX = iota
+	triPosY
+	triColorR
+	triColorG
+	triColorB
+	triColorA
+	triPicX
+	triPicY
+	triIntensity
+	triClipMinX
+	triClipMinY
+	triClipMaxX
+	triClipMaxY
+	trisAttrLen
 )
 
 // NewGLTriangles returns GLTriangles initialized with the data from the supplied Triangles.
 //
 // Only draw the Triangles using the provided Shader.
-func NewGLTriangles(shader *glhf.Shader, t pixel.Triangles) *GLTriangles {
+func NewGLTriangles(shader *GLShader, t pixel.Triangles) *GLTriangles {
 	var gt *GLTriangles
 	mainthread.Call(func() {
 		gt = &GLTriangles{
-			vs:     glhf.MakeVertexSlice(shader, 0, t.Len()),
+			vs:     glhf.MakeVertexSlice(shader.s, 0, t.Len()),
 			shader: shader,
 		}
 	})
@@ -48,7 +68,7 @@ func (gt *GLTriangles) VertexSlice() *glhf.VertexSlice {
 }
 
 // Shader returns the GLTriangles's associated shader.
-func (gt *GLTriangles) Shader() *glhf.Shader {
+func (gt *GLTriangles) Shader() *GLShader {
 	return gt.shader
 }
 
@@ -70,6 +90,7 @@ func (gt *GLTriangles) SetLen(length int) {
 				1, 1, 1, 1,
 				0, 0,
 				0,
+				0, 0, 0, 0,
 			)
 		}
 	case length < gt.Len():
@@ -110,17 +131,22 @@ func (gt *GLTriangles) updateData(t pixel.Triangles) {
 				col    = (*t)[i].Color
 				tx, ty = (*t)[i].Picture.XY()
 				in     = (*t)[i].Intensity
+				rec    = (*t)[i].ClipRect
 			)
-			d := gt.data[i*stride : i*stride+9]
+			d := gt.data[i*stride : i*stride+trisAttrLen]
-			d[0] = float32(px)
+			d[triPosX] = float32(px)
-			d[1] = float32(py)
+			d[triPosY] = float32(py)
-			d[2] = float32(col.R)
+			d[triColorR] = float32(col.R)
-			d[3] = float32(col.G)
+			d[triColorG] = float32(col.G)
-			d[4] = float32(col.B)
+			d[triColorB] = float32(col.B)
-			d[5] = float32(col.A)
+			d[triColorA] = float32(col.A)
-			d[6] = float32(tx)
+			d[triPicX] = float32(tx)
-			d[7] = float32(ty)
+			d[triPicY] = float32(ty)
-			d[8] = float32(in)
+			d[triIntensity] = float32(in)
+			d[triClipMinX] = float32(rec.Min.X)
+			d[triClipMinY] = float32(rec.Min.Y)
+			d[triClipMaxX] = float32(rec.Max.X)
+			d[triClipMaxY] = float32(rec.Max.Y)
 		}
 		return
 	}
@@ -128,25 +154,34 @@ func (gt *GLTriangles) updateData(t pixel.Triangles) {
 	if t, ok := t.(pixel.TrianglesPosition); ok {
 		for i := 0; i < length; i++ {
 			px, py := t.Position(i).XY()
-			gt.data[i*stride+0] = float32(px)
+			gt.data[i*stride+triPosX] = float32(px)
-			gt.data[i*stride+1] = float32(py)
+			gt.data[i*stride+triPosY] = float32(py)
 		}
 	}
 	if t, ok := t.(pixel.TrianglesColor); ok {
 		for i := 0; i < length; i++ {
 			col := t.Color(i)
-			gt.data[i*stride+2] = float32(col.R)
+			gt.data[i*stride+triColorR] = float32(col.R)
-			gt.data[i*stride+3] = float32(col.G)
+			gt.data[i*stride+triColorG] = float32(col.G)
-			gt.data[i*stride+4] = float32(col.B)
+			gt.data[i*stride+triColorB] = float32(col.B)
-			gt.data[i*stride+5] = float32(col.A)
+			gt.data[i*stride+triColorA] = float32(col.A)
 		}
 	}
 	if t, ok := t.(pixel.TrianglesPicture); ok {
 		for i := 0; i < length; i++ {
 			pic, intensity := t.Picture(i)
-			gt.data[i*stride+6] = float32(pic.X)
+			gt.data[i*stride+triPicX] = float32(pic.X)
-			gt.data[i*stride+7] = float32(pic.Y)
+			gt.data[i*stride+triPicY] = float32(pic.Y)
-			gt.data[i*stride+8] = float32(intensity)
+			gt.data[i*stride+triIntensity] = float32(intensity)
+		}
+	}
+	if t, ok := t.(pixel.TrianglesClipped); ok {
+		for i := 0; i < length; i++ {
+			rect, _ := t.ClipRect(i)
+			gt.data[i*stride+triClipMinX] = float32(rect.Min.X)
+			gt.data[i*stride+triClipMinY] = float32(rect.Min.Y)
+			gt.data[i*stride+triClipMaxX] = float32(rect.Max.X)
+			gt.data[i*stride+triClipMaxY] = float32(rect.Max.Y)
 		}
 	}
 }
@@ -160,6 +195,12 @@ func (gt *GLTriangles) Update(t pixel.Triangles) {
 	}
 	gt.updateData(t)
 
+	// Copy the verteces down to the glhf.VertexData
+	gt.CopyVertices()
+}
+
+// CopyVertices copies the GLTriangle data down to the vertex data.
+func (gt *GLTriangles) CopyVertices() {
 	// this code is supposed to copy the vertex data and CallNonBlock the update if
 	// the data is small enough, otherwise it'll block and not copy the data
 	if len(gt.data) < 256 { // arbitrary heurestic constant
@@ -185,19 +226,31 @@ func (gt *GLTriangles) Copy() pixel.Triangles {
 	return NewGLTriangles(gt.shader, gt)
 }
 
+// index is a helper function that returns the index in the data
+//	slice given the i-th vertex and the item index.
+func (gt *GLTriangles) index(i, idx int) int {
+	return i*gt.vs.Stride() + idx
+}
+
 // Position returns the Position property of the i-th vertex.
 func (gt *GLTriangles) Position(i int) pixel.Vec {
-	px := gt.data[i*gt.vs.Stride()+0]
+	px := gt.data[gt.index(i, triPosX)]
-	py := gt.data[i*gt.vs.Stride()+1]
+	py := gt.data[gt.index(i, triPosY)]
 	return pixel.V(float64(px), float64(py))
 }
 
+// SetPosition sets the position property of the i-th vertex.
+func (gt *GLTriangles) SetPosition(i int, p pixel.Vec) {
+	gt.data[gt.index(i, triPosX)] = float32(p.X)
+	gt.data[gt.index(i, triPosY)] = float32(p.Y)
+}
+
 // Color returns the Color property of the i-th vertex.
 func (gt *GLTriangles) Color(i int) pixel.RGBA {
-	r := gt.data[i*gt.vs.Stride()+2]
+	r := gt.data[gt.index(i, triColorR)]
-	g := gt.data[i*gt.vs.Stride()+3]
+	g := gt.data[gt.index(i, triColorG)]
-	b := gt.data[i*gt.vs.Stride()+4]
+	b := gt.data[gt.index(i, triColorB)]
-	a := gt.data[i*gt.vs.Stride()+5]
+	a := gt.data[gt.index(i, triColorA)]
 	return pixel.RGBA{
 		R: float64(r),
 		G: float64(g),
@@ -206,10 +259,44 @@ func (gt *GLTriangles) Color(i int) pixel.RGBA {
 	}
 }
 
+// SetColor sets the color property of the i-th vertex.
+func (gt *GLTriangles) SetColor(i int, c pixel.RGBA) {
+	gt.data[gt.index(i, triColorR)] = float32(c.R)
+	gt.data[gt.index(i, triColorG)] = float32(c.G)
+	gt.data[gt.index(i, triColorB)] = float32(c.B)
+	gt.data[gt.index(i, triColorA)] = float32(c.A)
+}
+
 // Picture returns the Picture property of the i-th vertex.
 func (gt *GLTriangles) Picture(i int) (pic pixel.Vec, intensity float64) {
-	tx := gt.data[i*gt.vs.Stride()+6]
+	tx := gt.data[gt.index(i, triPicX)]
-	ty := gt.data[i*gt.vs.Stride()+7]
+	ty := gt.data[gt.index(i, triPicY)]
-	intensity = float64(gt.data[i*gt.vs.Stride()+8])
+	intensity = float64(gt.data[gt.index(i, triIntensity)])
 	return pixel.V(float64(tx), float64(ty)), intensity
 }
+
+// SetPicture sets the picture property of the i-th vertex.
+func (gt *GLTriangles) SetPicture(i int, pic pixel.Vec, intensity float64) {
+	gt.data[gt.index(i, triPicX)] = float32(pic.X)
+	gt.data[gt.index(i, triPicY)] = float32(pic.Y)
+	gt.data[gt.index(i, triIntensity)] = float32(intensity)
+}
+
+// ClipRect returns the Clipping rectangle property of the i-th vertex.
+func (gt *GLTriangles) ClipRect(i int) (rect pixel.Rect, is bool) {
+	mx := gt.data[gt.index(i, triClipMinX)]
+	my := gt.data[gt.index(i, triClipMinY)]
+	ax := gt.data[gt.index(i, triClipMaxX)]
+	ay := gt.data[gt.index(i, triClipMaxY)]
+	rect = pixel.R(float64(mx), float64(my), float64(ax), float64(ay))
+	is = rect.Area() != 0.0
+	return
+}
+
+// SetClipRect sets the Clipping rectangle property of the i-th vertex.
+func (gt *GLTriangles) SetClipRect(i int, rect pixel.Rect) {
+	gt.data[gt.index(i, triClipMinX)] = float32(rect.Min.X)
+	gt.data[gt.index(i, triClipMinY)] = float32(rect.Min.Y)
+	gt.data[gt.index(i, triClipMaxX)] = float32(rect.Max.X)
+	gt.data[gt.index(i, triClipMaxY)] = float32(rect.Max.Y)
+}

pixelgl/input.go

@@ -1,9 +1,11 @@
 package pixelgl
 
 import (
+	"time"
+
 	"github.com/faiface/mainthread"
 	"github.com/faiface/pixel"
-	"github.com/go-gl/glfw/v3.2/glfw"
+	"github.com/go-gl/glfw/v3.3/glfw"
 )
 
 // Pressed returns whether the Button is currently pressed down.
@@ -11,14 +13,14 @@ func (w *Window) Pressed(button Button) bool {
 	return w.currInp.buttons[button]
 }
 
-// JustPressed returns whether the Button has just been pressed down.
+// JustPressed returns whether the Button has been pressed in the last frame.
 func (w *Window) JustPressed(button Button) bool {
-	return w.currInp.buttons[button] && !w.prevInp.buttons[button]
+	return w.pressEvents[button]
 }
 
-// JustReleased returns whether the Button has just been released up.
+// JustReleased returns whether the Button has been released in the last frame.
 func (w *Window) JustReleased(button Button) bool {
-	return !w.currInp.buttons[button] && w.prevInp.buttons[button]
+	return w.releaseEvents[button]
 }
 
 // Repeated returns whether a repeat event has been triggered on button.
@@ -360,8 +362,10 @@ func (w *Window) initInput() {
 		w.window.SetMouseButtonCallback(func(_ *glfw.Window, button glfw.MouseButton, action glfw.Action, mod glfw.ModifierKey) {
 			switch action {
 			case glfw.Press:
+				w.tempPressEvents[Button(button)] = true
 				w.tempInp.buttons[Button(button)] = true
 			case glfw.Release:
+				w.tempReleaseEvents[Button(button)] = true
 				w.tempInp.buttons[Button(button)] = false
 			}
 		})
@@ -372,8 +376,10 @@ func (w *Window) initInput() {
 			}
 			switch action {
 			case glfw.Press:
+				w.tempPressEvents[Button(key)] = true
 				w.tempInp.buttons[Button(key)] = true
 			case glfw.Release:
+				w.tempReleaseEvents[Button(key)] = true
 				w.tempInp.buttons[Button(key)] = false
 			case glfw.Repeat:
 				w.tempInp.repeat[Button(key)] = true
@@ -408,10 +414,33 @@ func (w *Window) UpdateInput() {
 	mainthread.Call(func() {
 		glfw.PollEvents()
 	})
+	w.doUpdateInput()
+}
 
+// UpdateInputWait blocks until an event is received or a timeout. If timeout is 0
+// then it will wait indefinitely
+func (w *Window) UpdateInputWait(timeout time.Duration) {
+	mainthread.Call(func() {
+		if timeout <= 0 {
+			glfw.WaitEvents()
+		} else {
+			glfw.WaitEventsTimeout(timeout.Seconds())
+		}
+	})
+	w.doUpdateInput()
+}
+
+// internal input bookkeeping
+func (w *Window) doUpdateInput() {
 	w.prevInp = w.currInp
 	w.currInp = w.tempInp
 
+	w.pressEvents = w.tempPressEvents
+	w.releaseEvents = w.tempReleaseEvents
+
+	// Clear last frame's temporary status
+	w.tempPressEvents = [KeyLast + 1]bool{}
+	w.tempReleaseEvents = [KeyLast + 1]bool{}
 	w.tempInp.repeat = [KeyLast + 1]bool{}
 	w.tempInp.scroll = pixel.ZV
 	w.tempInp.typed = ""

pixelgl/joystick.go

@@ -1,10 +1,10 @@
 package pixelgl
 
 import (
-	"github.com/go-gl/glfw/v3.2/glfw"
+	"github.com/go-gl/glfw/v3.3/glfw"
 )
 
-// Joystick is a joystick or controller.
+// Joystick is a joystick or controller (gamepad).
 type Joystick int
 
 // List all of the joysticks.
@@ -29,6 +29,47 @@ const (
 	JoystickLast = Joystick(glfw.JoystickLast)
 )
 
+// GamepadAxis corresponds to a gamepad axis.
+type GamepadAxis int
+
+// Gamepad axis IDs.
+const (
+	AxisLeftX        = GamepadAxis(glfw.AxisLeftX)
+	AxisLeftY        = GamepadAxis(glfw.AxisLeftY)
+	AxisRightX       = GamepadAxis(glfw.AxisRightX)
+	AxisRightY       = GamepadAxis(glfw.AxisRightY)
+	AxisLeftTrigger  = GamepadAxis(glfw.AxisLeftTrigger)
+	AxisRightTrigger = GamepadAxis(glfw.AxisRightTrigger)
+	AxisLast         = GamepadAxis(glfw.AxisLast)
+)
+
+// GamepadButton corresponds to a gamepad button.
+type GamepadButton int
+
+// Gamepad button IDs.
+const (
+	ButtonA           = GamepadButton(glfw.ButtonA)
+	ButtonB           = GamepadButton(glfw.ButtonB)
+	ButtonX           = GamepadButton(glfw.ButtonX)
+	ButtonY           = GamepadButton(glfw.ButtonY)
+	ButtonLeftBumper  = GamepadButton(glfw.ButtonLeftBumper)
+	ButtonRightBumper = GamepadButton(glfw.ButtonRightBumper)
+	ButtonBack        = GamepadButton(glfw.ButtonBack)
+	ButtonStart       = GamepadButton(glfw.ButtonStart)
+	ButtonGuide       = GamepadButton(glfw.ButtonGuide)
+	ButtonLeftThumb   = GamepadButton(glfw.ButtonLeftThumb)
+	ButtonRightThumb  = GamepadButton(glfw.ButtonRightThumb)
+	ButtonDpadUp      = GamepadButton(glfw.ButtonDpadUp)
+	ButtonDpadRight   = GamepadButton(glfw.ButtonDpadRight)
+	ButtonDpadDown    = GamepadButton(glfw.ButtonDpadDown)
+	ButtonDpadLeft    = GamepadButton(glfw.ButtonDpadLeft)
+	ButtonLast        = GamepadButton(glfw.ButtonLast)
+	ButtonCross       = GamepadButton(glfw.ButtonCross)
+	ButtonCircle      = GamepadButton(glfw.ButtonCircle)
+	ButtonSquare      = GamepadButton(glfw.ButtonSquare)
+	ButtonTriangle    = GamepadButton(glfw.ButtonTriangle)
+)
+
 // JoystickPresent returns if the joystick is currently connected.
 //
 // This API is experimental.
@@ -62,54 +103,61 @@ func (w *Window) JoystickAxisCount(js Joystick) int {
 // If the button index is out of range, this will return false.
 //
 // This API is experimental.
-func (w *Window) JoystickPressed(js Joystick, button int) bool {
+func (w *Window) JoystickPressed(js Joystick, button GamepadButton) bool {
-	return w.currJoy.getButton(js, button)
+	return w.currJoy.getButton(js, int(button))
 }
 
 // JoystickJustPressed returns whether the joystick Button has just been pressed down.
 // If the button index is out of range, this will return false.
 //
 // This API is experimental.
-func (w *Window) JoystickJustPressed(js Joystick, button int) bool {
+func (w *Window) JoystickJustPressed(js Joystick, button GamepadButton) bool {
-	return w.currJoy.getButton(js, button) && !w.prevJoy.getButton(js, button)
+	return w.currJoy.getButton(js, int(button)) && !w.prevJoy.getButton(js, int(button))
 }
 
 // JoystickJustReleased returns whether the joystick Button has just been released up.
 // If the button index is out of range, this will return false.
 //
 // This API is experimental.
-func (w *Window) JoystickJustReleased(js Joystick, button int) bool {
+func (w *Window) JoystickJustReleased(js Joystick, button GamepadButton) bool {
-	return !w.currJoy.getButton(js, button) && w.prevJoy.getButton(js, button)
+	return !w.currJoy.getButton(js, int(button)) && w.prevJoy.getButton(js, int(button))
 }
 
 // JoystickAxis returns the value of a joystick axis at the last call to Window.Update.
 // If the axis index is out of range, this will return 0.
 //
 // This API is experimental.
-func (w *Window) JoystickAxis(js Joystick, axis int) float64 {
+func (w *Window) JoystickAxis(js Joystick, axis GamepadAxis) float64 {
-	return w.currJoy.getAxis(js, axis)
+	return w.currJoy.getAxis(js, int(axis))
 }
 
 // Used internally during Window.UpdateInput to update the state of the joysticks.
 func (w *Window) updateJoystickInput() {
 	for js := Joystick1; js <= JoystickLast; js++ {
 		// Determine and store if the joystick was connected
-		joystickPresent := glfw.JoystickPresent(glfw.Joystick(js))
+		joystickPresent := glfw.Joystick(js).Present()
 		w.tempJoy.connected[js] = joystickPresent
 
 		if joystickPresent {
-			w.tempJoy.buttons[js] = glfw.GetJoystickButtons(glfw.Joystick(js))
+			if glfw.Joystick(js).IsGamepad() {
-			w.tempJoy.axis[js] = glfw.GetJoystickAxes(glfw.Joystick(js))
+				gamepadInputs := glfw.Joystick(js).GetGamepadState()
+
+				w.tempJoy.buttons[js] = gamepadInputs.Buttons[:]
+				w.tempJoy.axis[js] = gamepadInputs.Axes[:]
+			} else {
+				w.tempJoy.buttons[js] = glfw.Joystick(js).GetButtons()
+				w.tempJoy.axis[js] = glfw.Joystick(js).GetAxes()
+			}
 
 			if !w.currJoy.connected[js] {
 				// The joystick was recently connected, we get the name
-				w.tempJoy.name[js] = glfw.GetJoystickName(glfw.Joystick(js))
+				w.tempJoy.name[js] = glfw.Joystick(js).GetName()
 			} else {
 				// Use the name from the previous one
 				w.tempJoy.name[js] = w.currJoy.name[js]
 			}
 		} else {
-			w.tempJoy.buttons[js] = []byte{}
+			w.tempJoy.buttons[js] = []glfw.Action{}
 			w.tempJoy.axis[js] = []float32{}
 			w.tempJoy.name[js] = ""
 		}
@@ -122,7 +170,7 @@ func (w *Window) updateJoystickInput() {
 type joystickState struct {
 	connected [JoystickLast + 1]bool
 	name      [JoystickLast + 1]string
-	buttons   [JoystickLast + 1][]byte
+	buttons   [JoystickLast + 1][]glfw.Action
 	axis      [JoystickLast + 1][]float32
 }
 
@@ -132,7 +180,7 @@ func (js *joystickState) getButton(joystick Joystick, button int) bool {
 	if js.buttons[joystick] == nil || button >= len(js.buttons[joystick]) || button < 0 {
 		return false
 	}
-	return js.buttons[joystick][byte(button)] == 1
+	return js.buttons[joystick][byte(button)] == glfw.Press
 }
 
 // Returns the value of a joystick axis, returning 0 if the button or joystick is invalid.

pixelgl/monitor.go

@@ -2,7 +2,7 @@ package pixelgl
 
 import (
 	"github.com/faiface/mainthread"
-	"github.com/go-gl/glfw/v3.2/glfw"
+	"github.com/go-gl/glfw/v3.3/glfw"
 )
 
 // Monitor represents a physical display attached to your computer.

pixelgl/run.go

@@ -2,7 +2,7 @@ package pixelgl
 
 import (
 	"github.com/faiface/mainthread"
-	"github.com/go-gl/glfw/v3.2/glfw"
+	"github.com/go-gl/glfw/v3.3/glfw"
 	"github.com/pkg/errors"
 )
 

pixelgl/window.go

@@ -1,6 +1,7 @@
 package pixelgl
 
 import (
+	"fmt"
 	"image"
 	"image/color"
 	"runtime"
@@ -8,7 +9,8 @@ import (
 	"github.com/faiface/glhf"
 	"github.com/faiface/mainthread"
 	"github.com/faiface/pixel"
-	"github.com/go-gl/glfw/v3.2/glfw"
+	"github.com/go-gl/gl/v3.3-core/gl"
+	"github.com/go-gl/glfw/v3.3/glfw"
 	"github.com/pkg/errors"
 )
 
@@ -36,14 +38,17 @@ type WindowConfig struct {
 	// Bounds specify the bounds of the Window in pixels.
 	Bounds pixel.Rect
 
+	// Initial window position
+	Position pixel.Vec
+
 	// If set to nil, the Window will be windowed. Otherwise it will be fullscreen on the
 	// specified Monitor.
 	Monitor *Monitor
 
-	// Whether the Window is resizable.
+	// Resizable specifies whether the window will be resizable by the user.
 	Resizable bool
 
-	// Undecorated Window ommits the borders and decorations (close button, etc.).
+	// Undecorated Window omits the borders and decorations (close button, etc.).
 	Undecorated bool
 
 	// NoIconify specifies whether fullscreen windows should not automatically
@@ -56,9 +61,25 @@ type WindowConfig struct {
 	// implement proper full screen windows.
 	AlwaysOnTop bool
 
+	// TransparentFramebuffer specifies whether the window framebuffer will be
+	// transparent. If enabled and supported by the system, the window
+	// framebuffer alpha channel will be used to combine the framebuffer with
+	// the background. This does not affect window decorations.
+	TransparentFramebuffer bool
+
 	// VSync (vertical synchronization) synchronizes Window's framerate with the framerate of
 	// the monitor.
 	VSync bool
+
+	// Maximized specifies whether the window is maximized.
+	Maximized bool
+
+	// Invisible specifies whether the window will be initially hidden.
+	// You can make the window visible later using Window.Show().
+	Invisible bool
+
+	//SamplesMSAA specifies the level of MSAA to be used. Must be one of 0, 2, 4, 8, 16. 0 to disable.
+	SamplesMSAA int
 }
 
 // Window is a window handler. Use this type to manipulate a window (input, drawing, etc.).
@@ -84,6 +105,9 @@ type Window struct {
 		typed   string
 	}
 
+	pressEvents, tempPressEvents     [KeyLast + 1]bool
+	releaseEvents, tempReleaseEvents [KeyLast + 1]bool
+
 	prevJoy, currJoy, tempJoy joystickState
 }
 
@@ -100,6 +124,17 @@ func NewWindow(cfg WindowConfig) (*Window, error) {
 
 	w := &Window{bounds: cfg.Bounds, cursorVisible: true}
 
+	flag := false
+	for _, v := range []int{0, 2, 4, 8, 16} {
+		if cfg.SamplesMSAA == v {
+			flag = true
+			break
+		}
+	}
+	if !flag {
+		return nil, fmt.Errorf("invalid value '%v' for msaaSamples", cfg.SamplesMSAA)
+	}
+
 	err := mainthread.CallErr(func() error {
 		var err error
 
@@ -112,6 +147,14 @@ func NewWindow(cfg WindowConfig) (*Window, error) {
 		glfw.WindowHint(glfw.Decorated, bool2int[!cfg.Undecorated])
 		glfw.WindowHint(glfw.Floating, bool2int[cfg.AlwaysOnTop])
 		glfw.WindowHint(glfw.AutoIconify, bool2int[!cfg.NoIconify])
+		glfw.WindowHint(glfw.TransparentFramebuffer, bool2int[cfg.TransparentFramebuffer])
+		glfw.WindowHint(glfw.Maximized, bool2int[cfg.Maximized])
+		glfw.WindowHint(glfw.Visible, bool2int[!cfg.Invisible])
+		glfw.WindowHint(glfw.Samples, cfg.SamplesMSAA)
+
+		if cfg.Position.X != 0 || cfg.Position.Y != 0 {
+			glfw.WindowHint(glfw.Visible, glfw.False)
+		}
 
 		var share *glfw.Window
 		if currWin != nil {
@@ -129,9 +172,15 @@ func NewWindow(cfg WindowConfig) (*Window, error) {
 			return err
 		}
 
+		if cfg.Position.X != 0 || cfg.Position.Y != 0 {
+			w.window.SetPos(int(cfg.Position.X), int(cfg.Position.Y))
+			w.window.Show()
+		}
+
 		// enter the OpenGL context
 		w.begin()
 		glhf.Init()
+		gl.Enable(gl.MULTISAMPLE)
 		w.end()
 
 		return nil
@@ -177,6 +226,17 @@ func (w *Window) Update() {
 	w.UpdateInput()
 }
 
+// ClipboardText returns the current value of the systems clipboard.
+func (w *Window) ClipboardText() string {
+	return w.window.GetClipboardString()
+}
+
+// SetClipboardText passes the given string to the underlying glfw window to set the
+//	systems clipboard.
+func (w *Window) SetClipboardText(text string) {
+	w.window.SetClipboardString(text)
+}
+
 // SwapBuffers swaps buffers. Call this to swap buffers without polling window events.
 // Note that Update invokes SwapBuffers.
 func (w *Window) SwapBuffers() {
@@ -374,6 +434,15 @@ func (w *Window) SetCursorVisible(visible bool) {
 	})
 }
 
+// SetCursorDisabled hides the cursor and provides unlimited virtual cursor movement
+// make cursor visible using SetCursorVisible
+func (w *Window) SetCursorDisabled() {
+	w.cursorVisible = false
+	mainthread.Call(func() {
+		w.window.SetInputMode(glfw.CursorMode, glfw.CursorDisabled)
+	})
+}
+
 // CursorVisible returns the visibility status of the mouse cursor.
 func (w *Window) CursorVisible() bool {
 	return w.cursorVisible
@@ -449,3 +518,27 @@ func (w *Window) Color(at pixel.Vec) pixel.RGBA {
 func (w *Window) Canvas() *Canvas {
 	return w.canvas
 }
+
+// Show makes the window visible, if it was previously hidden. If the window is
+// already visible or is in full screen mode, this function does nothing.
+func (w *Window) Show() {
+	mainthread.Call(func() {
+		w.window.Show()
+	})
+}
+
+// Clipboard returns the contents of the system clipboard.
+func (w *Window) Clipboard() string {
+	var clipboard string
+	mainthread.Call(func() {
+		clipboard = w.window.GetClipboardString()
+	})
+	return clipboard
+}
+
+// SetClipboardString sets the system clipboard to the specified UTF-8 encoded string.
+func (w *Window) SetClipboard(str string) {
+	mainthread.Call(func() {
+		w.window.SetClipboardString(str)
+	})
+}

rectangle.go

@@ -0,0 +1,284 @@
+package pixel
+
+import (
+	"fmt"
+	"math"
+)
+
+// Rect is a 2D rectangle aligned with the axes of the coordinate system. It is defined by two
+// points, Min and Max.
+//
+// The invariant should hold, that Max's components are greater or equal than Min's components
+// respectively.
+type Rect struct {
+	Min, Max Vec
+}
+
+// ZR is a zero rectangle.
+var ZR = Rect{Min: ZV, Max: ZV}
+
+// R returns a new Rect with given the Min and Max coordinates.
+//
+// Note that the returned rectangle is not automatically normalized.
+func R(minX, minY, maxX, maxY float64) Rect {
+	return Rect{
+		Min: Vec{minX, minY},
+		Max: Vec{maxX, maxY},
+	}
+}
+
+// String returns the string representation of the Rect.
+//
+//   r := pixel.R(100, 50, 200, 300)
+//   r.String()     // returns "Rect(100, 50, 200, 300)"
+//   fmt.Println(r) // Rect(100, 50, 200, 300)
+func (r Rect) String() string {
+	return fmt.Sprintf("Rect(%v, %v, %v, %v)", r.Min.X, r.Min.Y, r.Max.X, r.Max.Y)
+}
+
+// Norm returns the Rect in normal form, such that Max is component-wise greater or equal than Min.
+func (r Rect) Norm() Rect {
+	return Rect{
+		Min: Vec{
+			math.Min(r.Min.X, r.Max.X),
+			math.Min(r.Min.Y, r.Max.Y),
+		},
+		Max: Vec{
+			math.Max(r.Min.X, r.Max.X),
+			math.Max(r.Min.Y, r.Max.Y),
+		},
+	}
+}
+
+// W returns the width of the Rect.
+func (r Rect) W() float64 {
+	return r.Max.X - r.Min.X
+}
+
+// H returns the height of the Rect.
+func (r Rect) H() float64 {
+	return r.Max.Y - r.Min.Y
+}
+
+// Size returns the vector of width and height of the Rect.
+func (r Rect) Size() Vec {
+	return V(r.W(), r.H())
+}
+
+// Area returns the area of r. If r is not normalized, area may be negative.
+func (r Rect) Area() float64 {
+	return r.W() * r.H()
+}
+
+// Edges will return the four lines which make up the edges of the rectangle.
+func (r Rect) Edges() [4]Line {
+	corners := r.Vertices()
+
+	return [4]Line{
+		{A: corners[0], B: corners[1]},
+		{A: corners[1], B: corners[2]},
+		{A: corners[2], B: corners[3]},
+		{A: corners[3], B: corners[0]},
+	}
+}
+
+// Anchor is a vector used to define anchors, such as `Center`, `Top`, `TopRight`, etc.
+type Anchor Vec
+
+var (
+	Center      = Anchor{0.5, 0.5}
+	Top         = Anchor{0.5, 0}
+	TopRight    = Anchor{0, 0}
+	Right       = Anchor{0, 0.5}
+	BottomRight = Anchor{0, 1}
+	Bottom      = Anchor{0.5, 1}
+	BottomLeft  = Anchor{1, 1}
+	Left        = Anchor{1, 0.5}
+	TopLeft     = Anchor{1, 0}
+)
+
+var anchorStrings map[Anchor]string = map[Anchor]string{
+	Center:      "center",
+	Top:         "top",
+	TopRight:    "top-right",
+	Right:       "right",
+	BottomRight: "bottom-right",
+	Bottom:      "bottom",
+	BottomLeft:  "bottom-left",
+	Left:        "left",
+	TopLeft:     "top-left",
+}
+
+// String returns the string representation of an anchor.
+func (anchor Anchor) String() string {
+	return anchorStrings[anchor]
+}
+
+var oppositeAnchors map[Anchor]Anchor = map[Anchor]Anchor{
+	Center:      Center,
+	Top:         Bottom,
+	Bottom:      Top,
+	Right:       Left,
+	Left:        Right,
+	TopRight:    BottomLeft,
+	BottomLeft:  TopRight,
+	BottomRight: TopLeft,
+	TopLeft:     BottomRight,
+}
+
+// Opposite returns the opposite position of the anchor (ie. Top -> Bottom; BottomLeft -> TopRight, etc.).
+func (anchor Anchor) Opposite() Anchor {
+	return oppositeAnchors[anchor]
+}
+
+// AnchorPos returns the relative position of the given anchor.
+func (r Rect) AnchorPos(anchor Anchor) Vec {
+	return r.Size().ScaledXY(V(0, 0).Sub(Vec(anchor)))
+}
+
+// AlignedTo returns the rect moved by the given anchor.
+func (rect Rect) AlignedTo(anchor Anchor) Rect {
+	return rect.Moved(rect.AnchorPos(anchor))
+}
+
+// Center returns the position of the center of the Rect.
+// `rect.Center()` is equivalent to `rect.Anchor(pixel.Anchor.Center)`
+func (r Rect) Center() Vec {
+	return Lerp(r.Min, r.Max, 0.5)
+}
+
+// Moved returns the Rect moved (both Min and Max) by the given vector delta.
+func (r Rect) Moved(delta Vec) Rect {
+	return Rect{
+		Min: r.Min.Add(delta),
+		Max: r.Max.Add(delta),
+	}
+}
+
+// Resized returns the Rect resized to the given size while keeping the position of the given
+// anchor.
+//
+//   r.Resized(r.Min, size)      // resizes while keeping the position of the lower-left corner
+//   r.Resized(r.Max, size)      // same with the top-right corner
+//   r.Resized(r.Center(), size) // resizes around the center
+//
+// This function does not make sense for resizing a rectangle of zero area and will panic. Use
+// ResizedMin in the case of zero area.
+func (r Rect) Resized(anchor, size Vec) Rect {
+	if r.W()*r.H() == 0 {
+		panic(fmt.Errorf("(%T).Resize: zero area", r))
+	}
+	fraction := Vec{size.X / r.W(), size.Y / r.H()}
+	return Rect{
+		Min: anchor.Add(r.Min.Sub(anchor).ScaledXY(fraction)),
+		Max: anchor.Add(r.Max.Sub(anchor).ScaledXY(fraction)),
+	}
+}
+
+// ResizedMin returns the Rect resized to the given size while keeping the position of the Rect's
+// Min.
+//
+// Sizes of zero area are safe here.
+func (r Rect) ResizedMin(size Vec) Rect {
+	return Rect{
+		Min: r.Min,
+		Max: r.Min.Add(size),
+	}
+}
+
+// Contains checks whether a vector u is contained within this Rect (including it's borders).
+func (r Rect) Contains(u Vec) bool {
+	return r.Min.X <= u.X && u.X <= r.Max.X && r.Min.Y <= u.Y && u.Y <= r.Max.Y
+}
+
+// Union returns the minimal Rect which covers both r and s. Rects r and s must be normalized.
+func (r Rect) Union(s Rect) Rect {
+	return R(
+		math.Min(r.Min.X, s.Min.X),
+		math.Min(r.Min.Y, s.Min.Y),
+		math.Max(r.Max.X, s.Max.X),
+		math.Max(r.Max.Y, s.Max.Y),
+	)
+}
+
+// Intersect returns the maximal Rect which is covered by both r and s. Rects r and s must be normalized.
+//
+// If r and s don't overlap, this function returns a zero-rectangle.
+func (r Rect) Intersect(s Rect) Rect {
+	t := R(
+		math.Max(r.Min.X, s.Min.X),
+		math.Max(r.Min.Y, s.Min.Y),
+		math.Min(r.Max.X, s.Max.X),
+		math.Min(r.Max.Y, s.Max.Y),
+	)
+	if t.Min.X >= t.Max.X || t.Min.Y >= t.Max.Y {
+		return ZR
+	}
+	return t
+}
+
+// Intersects returns whether or not the given Rect intersects at any point with this Rect.
+//
+// This function is overall about 5x faster than Intersect, so it is better
+// to use if you have no need for the returned Rect from Intersect.
+func (r Rect) Intersects(s Rect) bool {
+	return !(s.Max.X <= r.Min.X ||
+		s.Min.X >= r.Max.X ||
+		s.Max.Y <= r.Min.Y ||
+		s.Min.Y >= r.Max.Y)
+}
+
+// IntersectCircle returns a minimal required Vector, such that moving the rect by that vector would stop the Circle
+// and the Rect intersecting.  This function returns a zero-vector if the Circle and Rect do not overlap, and if only
+// the perimeters touch.
+//
+// This function will return a non-zero vector if:
+//  - The Rect contains the Circle, partially or fully
+//  - The Circle contains the Rect, partially of fully
+func (r Rect) IntersectCircle(c Circle) Vec {
+	return c.IntersectRect(r).Scaled(-1)
+}
+
+// IntersectLine will return the shortest Vec such that if the Rect is moved by the Vec returned, the Line and Rect no
+// longer intersect.
+func (r Rect) IntersectLine(l Line) Vec {
+	return l.IntersectRect(r).Scaled(-1)
+}
+
+// IntersectionPoints returns all the points where the Rect intersects with the line provided.  This can be zero, one or
+// two points, depending on the location of the shapes.  The points of intersection will be returned in order of
+// closest-to-l.A to closest-to-l.B.
+func (r Rect) IntersectionPoints(l Line) []Vec {
+	// Use map keys to ensure unique points
+	pointMap := make(map[Vec]struct{})
+
+	for _, edge := range r.Edges() {
+		if intersect, ok := l.Intersect(edge); ok {
+			pointMap[intersect] = struct{}{}
+		}
+	}
+
+	points := make([]Vec, 0, len(pointMap))
+	for point := range pointMap {
+		points = append(points, point)
+	}
+
+	// Order the points
+	if len(points) == 2 {
+		if points[1].To(l.A).Len() < points[0].To(l.A).Len() {
+			return []Vec{points[1], points[0]}
+		}
+	}
+
+	return points
+}
+
+// Vertices returns a slice of the four corners which make up the rectangle.
+func (r Rect) Vertices() [4]Vec {
+	return [4]Vec{
+		r.Min,
+		V(r.Min.X, r.Max.Y),
+		r.Max,
+		V(r.Max.X, r.Min.Y),
+	}
+}

rectangle_test.go

@@ -0,0 +1,384 @@
+package pixel_test
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"github.com/faiface/pixel"
+)
+
+func TestRect_Resize(t *testing.T) {
+	type rectTestTransform struct {
+		name string
+		f    func(pixel.Rect) pixel.Rect
+	}
+
+	// rectangles
+	squareAroundOrigin := pixel.R(-10, -10, 10, 10)
+	squareAround2020 := pixel.R(10, 10, 30, 30)
+	rectangleAroundOrigin := pixel.R(-20, -10, 20, 10)
+	rectangleAround2020 := pixel.R(0, 10, 40, 30)
+
+	// resize transformations
+	resizeByHalfAroundCenter := rectTestTransform{"by half around center", func(rect pixel.Rect) pixel.Rect {
+		return rect.Resized(rect.Center(), rect.Size().Scaled(0.5))
+	}}
+	resizeByHalfAroundMin := rectTestTransform{"by half around Min", func(rect pixel.Rect) pixel.Rect {
+		return rect.Resized(rect.Min, rect.Size().Scaled(0.5))
+	}}
+	resizeByHalfAroundMax := rectTestTransform{"by half around Max", func(rect pixel.Rect) pixel.Rect {
+		return rect.Resized(rect.Max, rect.Size().Scaled(0.5))
+	}}
+	resizeByHalfAroundMiddleOfLeftSide := rectTestTransform{"by half around middle of left side", func(rect pixel.Rect) pixel.Rect {
+		return rect.Resized(pixel.V(rect.Min.X, rect.Center().Y), rect.Size().Scaled(0.5))
+	}}
+	resizeByHalfAroundOrigin := rectTestTransform{"by half around the origin", func(rect pixel.Rect) pixel.Rect {
+		return rect.Resized(pixel.ZV, rect.Size().Scaled(0.5))
+	}}
+
+	testCases := []struct {
+		input     pixel.Rect
+		transform rectTestTransform
+		answer    pixel.Rect
+	}{
+		{squareAroundOrigin, resizeByHalfAroundCenter, pixel.R(-5, -5, 5, 5)},
+		{squareAround2020, resizeByHalfAroundCenter, pixel.R(15, 15, 25, 25)},
+		{rectangleAroundOrigin, resizeByHalfAroundCenter, pixel.R(-10, -5, 10, 5)},
+		{rectangleAround2020, resizeByHalfAroundCenter, pixel.R(10, 15, 30, 25)},
+
+		{squareAroundOrigin, resizeByHalfAroundMin, pixel.R(-10, -10, 0, 0)},
+		{squareAround2020, resizeByHalfAroundMin, pixel.R(10, 10, 20, 20)},
+		{rectangleAroundOrigin, resizeByHalfAroundMin, pixel.R(-20, -10, 0, 0)},
+		{rectangleAround2020, resizeByHalfAroundMin, pixel.R(0, 10, 20, 20)},
+
+		{squareAroundOrigin, resizeByHalfAroundMax, pixel.R(0, 0, 10, 10)},
+		{squareAround2020, resizeByHalfAroundMax, pixel.R(20, 20, 30, 30)},
+		{rectangleAroundOrigin, resizeByHalfAroundMax, pixel.R(0, 0, 20, 10)},
+		{rectangleAround2020, resizeByHalfAroundMax, pixel.R(20, 20, 40, 30)},
+
+		{squareAroundOrigin, resizeByHalfAroundMiddleOfLeftSide, pixel.R(-10, -5, 0, 5)},
+		{squareAround2020, resizeByHalfAroundMiddleOfLeftSide, pixel.R(10, 15, 20, 25)},
+		{rectangleAroundOrigin, resizeByHalfAroundMiddleOfLeftSide, pixel.R(-20, -5, 0, 5)},
+		{rectangleAround2020, resizeByHalfAroundMiddleOfLeftSide, pixel.R(0, 15, 20, 25)},
+
+		{squareAroundOrigin, resizeByHalfAroundOrigin, pixel.R(-5, -5, 5, 5)},
+		{squareAround2020, resizeByHalfAroundOrigin, pixel.R(5, 5, 15, 15)},
+		{rectangleAroundOrigin, resizeByHalfAroundOrigin, pixel.R(-10, -5, 10, 5)},
+		{rectangleAround2020, resizeByHalfAroundOrigin, pixel.R(0, 5, 20, 15)},
+	}
+
+	for _, testCase := range testCases {
+		t.Run(fmt.Sprintf("Resize %v %s", testCase.input, testCase.transform.name), func(t *testing.T) {
+			testResult := testCase.transform.f(testCase.input)
+			if testResult != testCase.answer {
+				t.Errorf("Got: %v, wanted: %v\n", testResult, testCase.answer)
+			}
+		})
+	}
+}
+
+func TestRect_Edges(t *testing.T) {
+	type fields struct {
+		Min pixel.Vec
+		Max pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   [4]pixel.Line
+	}{
+		{
+			name:   "Get edges",
+			fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+			want: [4]pixel.Line{
+				pixel.L(pixel.V(0, 0), pixel.V(0, 10)),
+				pixel.L(pixel.V(0, 10), pixel.V(10, 10)),
+				pixel.L(pixel.V(10, 10), pixel.V(10, 0)),
+				pixel.L(pixel.V(10, 0), pixel.V(0, 0)),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := pixel.Rect{
+				Min: tt.fields.Min,
+				Max: tt.fields.Max,
+			}
+			if got := r.Edges(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Rect.Edges() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRect_Vertices(t *testing.T) {
+	type fields struct {
+		Min pixel.Vec
+		Max pixel.Vec
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		want   [4]pixel.Vec
+	}{
+		{
+			name:   "Get corners",
+			fields: fields{Min: pixel.V(0, 0), Max: pixel.V(10, 10)},
+			want: [4]pixel.Vec{
+				pixel.V(0, 0),
+				pixel.V(0, 10),
+				pixel.V(10, 10),
+				pixel.V(10, 0),
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := pixel.Rect{
+				Min: tt.fields.Min,
+				Max: tt.fields.Max,
+			}
+			if got := r.Vertices(); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Rect.Vertices() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRect_IntersectCircle(t *testing.T) {
+	type fields struct {
+		Min pixel.Vec
+		Max pixel.Vec
+	}
+	type args struct {
+		c pixel.Circle
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   pixel.Vec
+	}{
+		{
+			name:   "Rect.IntersectCircle(): no overlap",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(50, 50), 1)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle contains rect",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, 5), 10)},
+			want:   pixel.V(-15, 0),
+		},
+		{
+			name:   "Rect.IntersectCircle(): rect contains circle",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, 5), 1)},
+			want:   pixel.V(-6, 0),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps bottom-left corner",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(-0.5, -0.5), 1)},
+			want:   pixel.V(-0.2, -0.2),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps top-left corner",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(-0.5, 10.5), 1)},
+			want:   pixel.V(-0.2, 0.2),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps bottom-right corner",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(10.5, -0.5), 1)},
+			want:   pixel.V(0.2, -0.2),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps top-right corner",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(10.5, 10.5), 1)},
+			want:   pixel.V(0.2, 0.2),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps two corners",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(0, 5), 6)},
+			want:   pixel.V(6, 0),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps left edge",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(0, 5), 1)},
+			want:   pixel.V(1, 0),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps bottom edge",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, 0), 1)},
+			want:   pixel.V(0, 1),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps right edge",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(10, 5), 1)},
+			want:   pixel.V(-1, 0),
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle overlaps top edge",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, 10), 1)},
+			want:   pixel.V(0, -1),
+		},
+		{
+			name:   "Rect.IntersectCircle(): edge is tangent of left side",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(-1, 5), 1)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Rect.IntersectCircle(): edge is tangent of top side",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, -1), 1)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle above rectangle",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, 12), 1)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle below rectangle",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(5, -2), 1)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle left of rectangle",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(-1, 5), 1)},
+			want:   pixel.ZV,
+		},
+		{
+			name:   "Rect.IntersectCircle(): circle right of rectangle",
+			fields: fields{Min: pixel.ZV, Max: pixel.V(10, 10)},
+			args:   args{c: pixel.C(pixel.V(11, 5), 1)},
+			want:   pixel.ZV,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := pixel.Rect{
+				Min: tt.fields.Min,
+				Max: tt.fields.Max,
+			}
+			got := r.IntersectCircle(tt.args.c)
+			if !closeEnough(got.X, tt.want.X, 2) || !closeEnough(got.Y, tt.want.Y, 2) {
+				t.Errorf("Rect.IntersectCircle() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRect_IntersectionPoints(t *testing.T) {
+	type fields struct {
+		Min pixel.Vec
+		Max pixel.Vec
+	}
+	type args struct {
+		l pixel.Line
+	}
+	tests := []struct {
+		name   string
+		fields fields
+		args   args
+		want   []pixel.Vec
+	}{
+		{
+			name:   "No intersection points",
+			fields: fields{Min: pixel.V(1, 1), Max: pixel.V(5, 5)},
+			args:   args{l: pixel.L(pixel.V(-5, 0), pixel.V(-2, 2))},
+			want:   []pixel.Vec{},
+		},
+		{
+			name:   "One intersection point",
+			fields: fields{Min: pixel.V(1, 1), Max: pixel.V(5, 5)},
+			args:   args{l: pixel.L(pixel.V(2, 0), pixel.V(2, 3))},
+			want:   []pixel.Vec{pixel.V(2, 1)},
+		},
+		{
+			name:   "Two intersection points",
+			fields: fields{Min: pixel.V(1, 1), Max: pixel.V(5, 5)},
+			args:   args{l: pixel.L(pixel.V(0, 2), pixel.V(6, 2))},
+			want:   []pixel.Vec{pixel.V(1, 2), pixel.V(5, 2)},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			r := pixel.Rect{
+				Min: tt.fields.Min,
+				Max: tt.fields.Max,
+			}
+			if got := r.IntersectionPoints(tt.args.l); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Rect.IntersectPoints() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+var rectIntTests = []struct {
+	name      string
+	r1, r2    pixel.Rect
+	want      pixel.Rect
+	intersect bool
+}{
+	{
+		name: "Nothing touching",
+		r1:   pixel.R(0, 0, 10, 10),
+		r2:   pixel.R(21, 21, 40, 40),
+		want: pixel.ZR,
+	},
+	{
+		name: "Edge touching",
+		r1:   pixel.R(0, 0, 10, 10),
+		r2:   pixel.R(10, 10, 20, 20),
+		want: pixel.ZR,
+	},
+	{
+		name:      "Bit of overlap",
+		r1:        pixel.R(0, 0, 10, 10),
+		r2:        pixel.R(0, 9, 20, 20),
+		want:      pixel.R(0, 9, 10, 10),
+		intersect: true,
+	},
+	{
+		name:      "Fully overlapped",
+		r1:        pixel.R(0, 0, 10, 10),
+		r2:        pixel.R(0, 0, 10, 10),
+		want:      pixel.R(0, 0, 10, 10),
+		intersect: true,
+	},
+}
+
+func TestRect_Intersect(t *testing.T) {
+	for _, tt := range rectIntTests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.r1.Intersect(tt.r2); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("Rect.Intersect() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestRect_Intersects(t *testing.T) {
+	for _, tt := range rectIntTests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := tt.r1.Intersects(tt.r2); got != tt.intersect {
+				t.Errorf("Rect.Intersects() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

sprite.go

@@ -27,7 +27,7 @@ func NewSprite(pic Picture, frame Rect) *Sprite {
 	tri := MakeTrianglesData(6)
 	s := &Sprite{
 		tri: tri,
-		d:   Drawer{Triangles: tri},
+		d:   Drawer{Triangles: tri, Cached: true},
 	}
 	s.matrix = IM
 	s.mask = Alpha(1)
@@ -44,6 +44,13 @@ func (s *Sprite) Set(pic Picture, frame Rect) {
 	}
 }
 
+// SetCached makes the sprite cache all the
+// incoming pictures if the argument is true, and
+// doesn't make it do that if the argument is false.
+func (s *Sprite) SetCached(cached bool) {
+	s.d.Cached = cached
+}
+
 // Picture returns the current Sprite's Picture.
 func (s *Sprite) Picture() Picture {
 	return s.d.Picture

text/atlas.go

@@ -1,7 +1,6 @@
 package text
 
 import (
-	"fmt"
 	"image"
 	"image/draw"
 	"sort"
@@ -60,8 +59,9 @@ func NewAtlas(face font.Face, runeSets ...[]rune) *Atlas {
 	))
 
 	for r, fg := range fixedMapping {
-		dr, mask, maskp, _, _ := face.Glyph(fg.dot, r)
+		if dr, mask, maskp, _, ok := face.Glyph(fg.dot, r); ok {
-		draw.Draw(atlasImg, dr, mask, maskp, draw.Src)
+			draw.Draw(atlasImg, dr, mask, maskp, draw.Src)
+		}
 	}
 
 	bounds := pixel.R(
@@ -203,7 +203,6 @@ func makeMapping(face font.Face, runes []rune, padding, width fixed.Int26_6) (ma
 	for _, r := range runes {
 		b, advance, ok := face.GlyphBounds(r)
 		if !ok {
-			fmt.Println(r)
 			continue
 		}
 

text/atlas_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/faiface/pixel/text"
+	"golang.org/x/image/font/inconsolata"
 )
 
 func TestAtlas7x13(t *testing.T) {
@@ -22,3 +23,7 @@ func TestAtlas7x13(t *testing.T) {
 		}
 	}
 }
+
+func TestAtlasInconsolata(t *testing.T) {
+	text.NewAtlas(inconsolata.Regular8x16, text.ASCII)
+}

text/text.go

@@ -101,6 +101,7 @@ type Text struct {
 	trans  pixel.TrianglesData
 	transD pixel.Drawer
 	dirty  bool
+	anchor pixel.Anchor
 }
 
 // New creates a new Text capable of drawing runes contained in the provided Atlas. Orig and Dot
@@ -135,6 +136,7 @@ func New(orig pixel.Vec, atlas *Atlas) *Text {
 
 	txt.transD.Picture = txt.atlas.pic
 	txt.transD.Triangles = &txt.trans
+	txt.transD.Cached = true
 
 	txt.Clear()
 
@@ -182,6 +184,12 @@ func (txt *Text) BoundsOf(s string) pixel.Rect {
 	return bounds
 }
 
+// AlignedTo returns the text moved by the given anchor.
+func (txt *Text) AlignedTo(anchor pixel.Anchor) *Text {
+	txt.anchor = anchor
+	return txt
+}
+
 // Clear removes all written text from the Text. The Dot field is reset to Orig.
 func (txt *Text) Clear() {
 	txt.prevR = -1
@@ -244,6 +252,10 @@ func (txt *Text) DrawColorMask(t pixel.Target, matrix pixel.Matrix, mask color.C
 		txt.mat = matrix
 		txt.dirty = true
 	}
+
+	offset := txt.Orig.Sub(txt.Bounds().Max.Add(txt.Bounds().AnchorPos(txt.anchor.Opposite())))
+	txt.mat = pixel.IM.Moved(offset).Chained(txt.mat)
+
 	if mask == nil {
 		mask = pixel.Alpha(1)
 	}

text/text_test.go

@@ -76,7 +76,7 @@ func BenchmarkTextWrite(b *testing.B) {
 		b.Run(fmt.Sprintf("%d", len(chunk)), func(b *testing.B) {
 			txt := text.New(pixel.ZV, atlas)
 			for i := 0; i < b.N; i++ {
-				txt.Write(chunk)
+				_, _ = txt.Write(chunk)
 			}
 		})
 	}

vector.go

@@ -0,0 +1,462 @@
+package pixel
+
+import (
+	"fmt"
+	"math"
+)
+
+// Vec is a 2D vector type with X and Y coordinates.
+//
+// Create vectors with the V constructor:
+//
+//   u := pixel.V(1, 2)
+//   v := pixel.V(8, -3)
+//
+// Use various methods to manipulate them:
+//
+//   w := u.Add(v)
+//   fmt.Println(w)        // Vec(9, -1)
+//   fmt.Println(u.Sub(v)) // Vec(-7, 5)
+//   u = pixel.V(2, 3)
+//   v = pixel.V(8, 1)
+//   if u.X < 0 {
+//	     fmt.Println("this won't happen")
+//   }
+//   x := u.Unit().Dot(v.Unit())
+type Vec struct {
+	X, Y float64
+}
+
+// ZV is a zero vector.
+var ZV = Vec{0, 0}
+
+// V returns a new 2D vector with the given coordinates.
+func V(x, y float64) Vec {
+	return Vec{x, y}
+}
+
+// nearlyEqual compares two float64s and returns whether they are equal, accounting for rounding errors.At worst, the
+// result is correct to 7 significant digits.
+func nearlyEqual(a, b float64) bool {
+	epsilon := 0.000001
+
+	if a == b {
+		return true
+	}
+
+	diff := math.Abs(a - b)
+
+	if a == 0.0 || b == 0.0 || diff < math.SmallestNonzeroFloat64 {
+		return diff < (epsilon * math.SmallestNonzeroFloat64)
+	}
+
+	absA := math.Abs(a)
+	absB := math.Abs(b)
+
+	return diff/math.Min(absA+absB, math.MaxFloat64) < epsilon
+}
+
+// Eq will compare two vectors and return whether they are equal accounting for rounding errors.  At worst, the result
+// is correct to 7 significant digits.
+func (u Vec) Eq(v Vec) bool {
+	return nearlyEqual(u.X, v.X) && nearlyEqual(u.Y, v.Y)
+}
+
+// Unit returns a vector of length 1 facing the given angle.
+func Unit(angle float64) Vec {
+	return Vec{1, 0}.Rotated(angle)
+}
+
+// String returns the string representation of the vector u.
+//
+//   u := pixel.V(4.5, -1.3)
+//   u.String()     // returns "Vec(4.5, -1.3)"
+//   fmt.Println(u) // Vec(4.5, -1.3)
+func (u Vec) String() string {
+	return fmt.Sprintf("Vec(%v, %v)", u.X, u.Y)
+}
+
+// XY returns the components of the vector in two return values.
+func (u Vec) XY() (x, y float64) {
+	return u.X, u.Y
+}
+
+// Add returns the sum of vectors u and v.
+func (u Vec) Add(v Vec) Vec {
+	return Vec{
+		u.X + v.X,
+		u.Y + v.Y,
+	}
+}
+
+// Sub returns the difference betweeen vectors u and v.
+func (u Vec) Sub(v Vec) Vec {
+	return Vec{
+		u.X - v.X,
+		u.Y - v.Y,
+	}
+}
+
+// Floor converts x and y to their integer equivalents.
+func (u Vec) Floor() Vec {
+	return Vec{
+		math.Floor(u.X),
+		math.Floor(u.Y),
+	}
+}
+
+// To returns the vector from u to v. Equivalent to v.Sub(u).
+func (u Vec) To(v Vec) Vec {
+	return Vec{
+		v.X - u.X,
+		v.Y - u.Y,
+	}
+}
+
+// Scaled returns the vector u multiplied by c.
+func (u Vec) Scaled(c float64) Vec {
+	return Vec{u.X * c, u.Y * c}
+}
+
+// ScaledXY returns the vector u multiplied by the vector v component-wise.
+func (u Vec) ScaledXY(v Vec) Vec {
+	return Vec{u.X * v.X, u.Y * v.Y}
+}
+
+// Len returns the length of the vector u.
+func (u Vec) Len() float64 {
+	return math.Hypot(u.X, u.Y)
+}
+
+// SqLen returns the squared length of the vector u (faster to compute than Len).
+func (u Vec) SqLen() float64 {
+	return u.X*u.X + u.Y*u.Y
+}
+
+// Angle returns the angle between the vector u and the x-axis. The result is in range [-Pi, Pi].
+func (u Vec) Angle() float64 {
+	return math.Atan2(u.Y, u.X)
+}
+
+// Unit returns a vector of length 1 facing the direction of u (has the same angle).
+func (u Vec) Unit() Vec {
+	if u.X == 0 && u.Y == 0 {
+		return Vec{1, 0}
+	}
+	return u.Scaled(1 / u.Len())
+}
+
+// Rotated returns the vector u rotated by the given angle in radians.
+func (u Vec) Rotated(angle float64) Vec {
+	sin, cos := math.Sincos(angle)
+	return Vec{
+		u.X*cos - u.Y*sin,
+		u.X*sin + u.Y*cos,
+	}
+}
+
+// Normal returns a vector normal to u. Equivalent to u.Rotated(math.Pi / 2), but faster.
+func (u Vec) Normal() Vec {
+	return Vec{-u.Y, u.X}
+}
+
+// Dot returns the dot product of vectors u and v.
+func (u Vec) Dot(v Vec) float64 {
+	return u.X*v.X + u.Y*v.Y
+}
+
+// Cross return the cross product of vectors u and v.
+func (u Vec) Cross(v Vec) float64 {
+	return u.X*v.Y - v.X*u.Y
+}
+
+// Project returns a projection (or component) of vector u in the direction of vector v.
+//
+// Behaviour is undefined if v is a zero vector.
+func (u Vec) Project(v Vec) Vec {
+	len := u.Dot(v) / v.Len()
+	return v.Unit().Scaled(len)
+}
+
+// Map applies the function f to both x and y components of the vector u and returns the modified
+// vector.
+//
+//   u := pixel.V(10.5, -1.5)
+//   v := u.Map(math.Floor)   // v is Vec(10, -2), both components of u floored
+func (u Vec) Map(f func(float64) float64) Vec {
+	return Vec{
+		f(u.X),
+		f(u.Y),
+	}
+}
+
+// Lerp returns a linear interpolation between vectors a and b.
+//
+// This function basically returns a point along the line between a and b and t chooses which one.
+// If t is 0, then a will be returned, if t is 1, b will be returned. Anything between 0 and 1 will
+// return the appropriate point between a and b and so on.
+func Lerp(a, b Vec, t float64) Vec {
+	return a.Scaled(1 - t).Add(b.Scaled(t))
+}
+
+// Line is a 2D line segment, between points A and B.
+type Line struct {
+	A, B Vec
+}
+
+// L creates and returns a new Line.
+func L(from, to Vec) Line {
+	return Line{
+		A: from,
+		B: to,
+	}
+}
+
+// Bounds returns the lines bounding box.  This is in the form of a normalized Rect.
+func (l Line) Bounds() Rect {
+	return R(l.A.X, l.A.Y, l.B.X, l.B.Y).Norm()
+}
+
+// Center will return the point at center of the line; that is, the point equidistant from either end.
+func (l Line) Center() Vec {
+	return l.A.Add(l.A.To(l.B).Scaled(0.5))
+}
+
+// Closest will return the point on the line which is closest to the Vec provided.
+func (l Line) Closest(v Vec) Vec {
+	// between is a helper function which determines whether x is greater than min(a, b) and less than max(a, b)
+	between := func(a, b, x float64) bool {
+		min := math.Min(a, b)
+		max := math.Max(a, b)
+		return min < x && x < max
+	}
+
+	// Closest point will be on a line which perpendicular to this line.
+	// If and only if the infinite perpendicular line intersects the segment.
+	m, b := l.Formula()
+
+	// Account for horizontal lines
+	if m == 0 {
+		x := v.X
+		y := l.A.Y
+
+		// check if the X coordinate of v is on the line
+		if between(l.A.X, l.B.X, v.X) {
+			return V(x, y)
+		}
+
+		// Otherwise get the closest endpoint
+		if l.A.To(v).Len() < l.B.To(v).Len() {
+			return l.A
+		}
+		return l.B
+	}
+
+	// Account for vertical lines
+	if math.IsInf(math.Abs(m), 1) {
+		x := l.A.X
+		y := v.Y
+
+		// check if the Y coordinate of v is on the line
+		if between(l.A.Y, l.B.Y, v.Y) {
+			return V(x, y)
+		}
+
+		// Otherwise get the closest endpoint
+		if l.A.To(v).Len() < l.B.To(v).Len() {
+			return l.A
+		}
+		return l.B
+	}
+
+	perpendicularM := -1 / m
+	perpendicularB := v.Y - (perpendicularM * v.X)
+
+	// Coordinates of intersect (of infinite lines)
+	x := (perpendicularB - b) / (m - perpendicularM)
+	y := m*x + b
+
+	// Check if the point lies between the x and y bounds of the segment
+	if !between(l.A.X, l.B.X, x) && !between(l.A.Y, l.B.Y, y) {
+		// Not within bounding box
+		toStart := v.To(l.A)
+		toEnd := v.To(l.B)
+
+		if toStart.Len() < toEnd.Len() {
+			return l.A
+		}
+		return l.B
+	}
+
+	return V(x, y)
+}
+
+// Contains returns whether the provided Vec lies on the line.
+func (l Line) Contains(v Vec) bool {
+	return l.Closest(v).Eq(v)
+}
+
+// Formula will return the values that represent the line in the formula: y = mx + b
+// This function will return math.Inf+, math.Inf- for a vertical line.
+func (l Line) Formula() (m, b float64) {
+	// Account for horizontal lines
+	if l.B.Y == l.A.Y {
+		return 0, l.A.Y
+	}
+
+	m = (l.B.Y - l.A.Y) / (l.B.X - l.A.X)
+	b = l.A.Y - (m * l.A.X)
+
+	return m, b
+}
+
+// Intersect will return the point of intersection for the two line segments.  If the line segments do not intersect,
+// this function will return the zero-vector and false.
+func (l Line) Intersect(k Line) (Vec, bool) {
+	// Check if the lines are parallel
+	lDir := l.A.To(l.B)
+	kDir := k.A.To(k.B)
+	if lDir.X == kDir.X && lDir.Y == kDir.Y {
+		return ZV, false
+	}
+
+	// The lines intersect - but potentially not within the line segments.
+	// Get the intersection point for the lines if they were infinitely long, check if the point exists on both of the
+	// segments
+	lm, lb := l.Formula()
+	km, kb := k.Formula()
+
+	// Account for vertical lines
+	if math.IsInf(math.Abs(lm), 1) && math.IsInf(math.Abs(km), 1) {
+		// Both vertical, therefore parallel
+		return ZV, false
+	}
+
+	var x, y float64
+
+	if math.IsInf(math.Abs(lm), 1) || math.IsInf(math.Abs(km), 1) {
+		// One line is vertical
+		intersectM := lm
+		intersectB := lb
+		verticalLine := k
+
+		if math.IsInf(math.Abs(lm), 1) {
+			intersectM = km
+			intersectB = kb
+			verticalLine = l
+		}
+
+		y = intersectM*verticalLine.A.X + intersectB
+		x = verticalLine.A.X
+	} else {
+		// Coordinates of intersect
+		x = (kb - lb) / (lm - km)
+		y = lm*x + lb
+	}
+
+	if l.Contains(V(x, y)) && k.Contains(V(x, y)) {
+		// The intersect point is on both line segments, they intersect.
+		return V(x, y), true
+	}
+
+	return ZV, false
+}
+
+// IntersectCircle will return the shortest Vec such that moving the Line by that Vec will cause the Line and Circle
+// to no longer intesect.  If they do not intersect at all, this function will return a zero-vector.
+func (l Line) IntersectCircle(c Circle) Vec {
+	// Get the point on the line closest to the center of the circle.
+	closest := l.Closest(c.Center)
+	cirToClosest := c.Center.To(closest)
+
+	if cirToClosest.Len() >= c.Radius {
+		return ZV
+	}
+
+	return cirToClosest.Scaled(cirToClosest.Len() - c.Radius)
+}
+
+// IntersectRect will return the shortest Vec such that moving the Line by that Vec will cause  the Line and Rect to
+// no longer intesect.  If they do not intersect at all, this function will return a zero-vector.
+func (l Line) IntersectRect(r Rect) Vec {
+	// Check if either end of the line segment are within the rectangle
+	if r.Contains(l.A) || r.Contains(l.B) {
+		// Use the Rect.Intersect to get minimal return value
+		rIntersect := l.Bounds().Intersect(r)
+		if rIntersect.H() > rIntersect.W() {
+			// Go vertical
+			return V(0, rIntersect.H())
+		}
+		return V(rIntersect.W(), 0)
+	}
+
+	// Check if any of the rectangles' edges intersect with this line.
+	for _, edge := range r.Edges() {
+		if _, ok := l.Intersect(edge); ok {
+			// Get the closest points on the line to each corner, where:
+			//  - the point is contained by the rectangle
+			//  - the point is not the corner itself
+			corners := r.Vertices()
+			var closest *Vec
+			closestCorner := corners[0]
+			for _, c := range corners {
+				cc := l.Closest(c)
+				if closest == nil || (closest.Len() > cc.Len() && r.Contains(cc)) {
+					closest = &cc
+					closestCorner = c
+				}
+			}
+
+			return closest.To(closestCorner)
+		}
+	}
+
+	// No intersect
+	return ZV
+}
+
+// Len returns the length of the line segment.
+func (l Line) Len() float64 {
+	return l.A.To(l.B).Len()
+}
+
+// Moved will return a line moved by the delta Vec provided.
+func (l Line) Moved(delta Vec) Line {
+	return Line{
+		A: l.A.Add(delta),
+		B: l.B.Add(delta),
+	}
+}
+
+// Rotated will rotate the line around the provided Vec.
+func (l Line) Rotated(around Vec, angle float64) Line {
+	// Move the line so we can use `Vec.Rotated`
+	lineShifted := l.Moved(around.Scaled(-1))
+
+	lineRotated := Line{
+		A: lineShifted.A.Rotated(angle),
+		B: lineShifted.B.Rotated(angle),
+	}
+
+	return lineRotated.Moved(around)
+}
+
+// Scaled will return the line scaled around the center point.
+func (l Line) Scaled(scale float64) Line {
+	return l.ScaledXY(l.Center(), scale)
+}
+
+// ScaledXY will return the line scaled around the Vec provided.
+func (l Line) ScaledXY(around Vec, scale float64) Line {
+	toA := around.To(l.A).Scaled(scale)
+	toB := around.To(l.B).Scaled(scale)
+
+	return Line{
+		A: around.Add(toA),
+		B: around.Add(toB),
+	}
+}
+
+func (l Line) String() string {
+	return fmt.Sprintf("Line(%v, %v)", l.A, l.B)
+}

vector_test.go

@@ -0,0 +1,27 @@
+package pixel_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/faiface/pixel"
+)
+
+type floorTest struct {
+	input    pixel.Vec
+	expected pixel.Vec
+}
+
+func TestFloor(t *testing.T) {
+	tests := []floorTest{
+		{input: pixel.V(4.50, 6.70), expected: pixel.V(4, 6)},
+		{input: pixel.V(9.0, 6.70), expected: pixel.V(9, 6)},
+	}
+
+	for _, tc := range tests {
+		result := tc.input.Floor()
+		if result != tc.expected {
+			t.Error(fmt.Sprintf("Expected %v but got %v", tc.expected, result))
+		}
+	}
+}