Added line collisions example

community/line-collisions/main.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"image/color"
+
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/imdraw"
+	"github.com/faiface/pixel/pixelgl"
+)
+
+const (
+	modeR = iota
+	modeL
+)
+
+const (
+	clickLineA = iota
+	clickLineB
+)
+
+var (
+	winBounds = pixel.R(0, 0, 1024, 768)
+
+	r = pixel.R(10, 10, 70, 50)
+	l = pixel.L(pixel.V(20, 20), pixel.V(100, 30))
+
+	mode      = modeR
+	clickLine = clickLineA
+)
+
+func run() {
+	cfg := pixelgl.WindowConfig{
+		Title:  "Line collision",
+		Bounds: winBounds,
+		VSync:  true,
+	}
+
+	win, err := pixelgl.NewWindow(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	imd := imdraw.New(nil)
+
+	for !win.Closed() {
+		if mode == modeR {
+			win.Clear(color.RGBA{R: 23, G: 39, B: 58, A: 125})
+		} else {
+			win.Clear(color.RGBA{R: 21, G: 55, B: 18, A: 125})
+		}
+		imd.Clear()
+
+		if win.JustPressed(pixelgl.KeyR) {
+			mode = modeR
+		}
+		if win.JustPressed(pixelgl.KeyL) {
+			mode = modeL
+			clickLine = clickLineA
+		}
+
+		if win.JustPressed(pixelgl.MouseButtonLeft) {
+			if mode == modeR {
+				rectToMouse := r.Center().To(win.MousePosition())
+				r = r.Moved(rectToMouse)
+			}
+
+			if mode == modeL {
+				if clickLine == clickLineA {
+					l = pixel.L(win.MousePosition(), win.MousePosition().Add(pixel.V(1, 1)))
+					clickLine = clickLineB
+				} else {
+					l = pixel.L(l.A, win.MousePosition())
+					clickLine = clickLineA
+				}
+			}
+		}
+
+		imd.Color = color.Black
+		imd.Push(r.Min, r.Max)
+		imd.Rectangle(3)
+
+		imd.Color = color.RGBA{R: 10, G: 10, B: 250, A: 255}
+		imd.Push(l.A, l.B)
+		imd.Line(3)
+
+		imd.Color = color.RGBA{R: 250, G: 10, B: 10, A: 255}
+		for _, i := range r.IntersectionPoints(l) {
+			imd.Push(i)
+			imd.Circle(4, 0)
+		}
+
+		imd.Draw(win)
+		win.Update()
+	}
+}
+
+func main() {
+	pixelgl.Run(run)
+}