add orphan pixelgl functions

pixelgl/orphan.go

@@ -0,0 +1,14 @@
+package pixelgl
+
+import "github.com/go-gl/gl/v3.3-core/gl"
+
+// Clear clears the current framebuffer or window with the given color.
+func Clear(r, g, b, a float32) {
+	gl.ClearColor(r, g, b, a)
+	gl.Clear(gl.COLOR_BUFFER_BIT)
+}
+
+// Viewport sets the OpenGL viewport.
+func Viewport(x, y, w, h int32) {
+	gl.Viewport(x, y, w, h)
+}

window.go

@@ -6,7 +6,6 @@ import (
 	"runtime"
 
 	"github.com/faiface/pixel/pixelgl"
-	"github.com/go-gl/gl/v3.3-core/gl"
 	"github.com/go-gl/glfw/v3.2/glfw"
 	"github.com/go-gl/mathgl/mgl32"
 	"github.com/pkg/errors"
@@ -62,6 +61,9 @@ type Window struct {
 	config  WindowConfig
 	shader  *pixelgl.Shader
 
+	// cache
+	width, height float64
+
 	// Target stuff, Picture, transformation matrix and color
 	pic *Picture
 	mat mgl32.Mat3
@@ -170,8 +172,7 @@ func (w *Window) Clear(c color.Color) {
 		defer w.end()
 
 		c := NRGBAModel.Convert(c).(NRGBA)
-		gl.ClearColor(float32(c.R), float32(c.G), float32(c.B), float32(c.A))
-		gl.Clear(gl.COLOR_BUFFER_BIT)
+		pixelgl.Clear(float32(c.R), float32(c.G), float32(c.B), float32(c.A))
 	})
 }
 
@@ -179,23 +180,16 @@ func (w *Window) Clear(c color.Color) {
 func (w *Window) Update() {
 	pixelgl.Do(func() {
 		w.begin()
-		defer w.end()
-
 		if w.config.VSync {
 			glfw.SwapInterval(1)
 		}
 		w.window.SwapBuffers()
+		w.end()
 	})
 
 	w.updateInput()
 
-	pixelgl.Do(func() {
-		w.begin()
-		defer w.end()
-
-		w, h := w.window.GetSize()
-		gl.Viewport(0, 0, int32(w), int32(h))
-	})
+	w.width, w.height = w.Size()
 }
 
 // SetClosed sets the closed flag of a window.
@@ -352,6 +346,7 @@ func (w *Window) begin() {
 	if w.shader != nil {
 		w.shader.Begin()
 	}
+	pixelgl.Viewport(0, 0, int32(w.width), int32(w.height))
 }
 
 // Note: must be called inside the main thread.