graphics: Bug fix: glClear doesn't treat 0 or 1 correctly

Fixes #452

image_test.go

@@ -563,7 +563,7 @@ func TestImageEdge(t *testing.T) {
 
 // Issue #419
 func TestImageTooManyFill(t *testing.T) {
-	const width = 256
+	const width = 1024
 
 	src, _ := NewImage(1, 1, FilterNearest)
 	dst, _ := NewImage(width, 1, FilterNearest)

internal/graphics/command.go

@@ -201,10 +201,32 @@ func (c *fillCommand) Exec(indexOffsetInBytes int) error {
 
 	cr, cg, cb, ca := c.color.R, c.color.G, c.color.B, c.color.A
 	const max = math.MaxUint8
-	r := float64(cr) / max
-	g := float64(cg) / max
-	b := float64(cb) / max
-	a := float64(ca) / max
+	r := float32(cr) / max
+	g := float32(cg) / max
+	b := float32(cb) / max
+	a := float32(ca) / max
+
+	// On some machines like MacBook Pro, exact 0 and exact 1 might cause problems
+	// at glClear() (#452).
+	if r == 0 {
+		r = math.Nextafter32(r, 1)
+	}
+	if g == 0 {
+		g = math.Nextafter32(g, 1)
+	}
+	if b == 0 {
+		b = math.Nextafter32(b, 1)
+	}
+	if r == 1 {
+		r = math.Nextafter32(r, 0)
+	}
+	if g == 1 {
+		g = math.Nextafter32(g, 0)
+	}
+	if b == 1 {
+		b = math.Nextafter32(b, 0)
+	}
+
 	if err := opengl.GetContext().FillFramebuffer(r, g, b, a); err != nil {
 		return err
 	}

internal/opengl/context_desktop.go

@@ -281,9 +281,9 @@ func (c *Context) setViewportImpl(width, height int) {
 	})
 }
 
-func (c *Context) FillFramebuffer(r, g, b, a float64) error {
+func (c *Context) FillFramebuffer(r, g, b, a float32) error {
 	return c.runOnContextThread(func() error {
-		gl.ClearColor(float32(r), float32(g), float32(b), float32(a))
+		gl.ClearColor(r, g, b, a)
 		gl.Clear(gl.COLOR_BUFFER_BIT)
 		return nil
 	})

internal/opengl/context_js.go

@@ -252,10 +252,10 @@ func (c *Context) setViewportImpl(width, height int) {
 	gl.Viewport(0, 0, width, height)
 }
 
-func (c *Context) FillFramebuffer(r, g, b, a float64) error {
+func (c *Context) FillFramebuffer(r, g, b, a float32) error {
 	// TODO: Use f?
 	gl := c.gl
-	gl.ClearColor(float32(r), float32(g), float32(b), float32(a))
+	gl.ClearColor(r, g, b, a)
 	gl.Clear(gl.COLOR_BUFFER_BIT)
 	return nil
 }

internal/opengl/context_mobile.go

@@ -220,9 +220,9 @@ func (c *Context) setViewportImpl(width, height int) {
 	gl.Viewport(0, 0, width, height)
 }
 
-func (c *Context) FillFramebuffer(r, g, b, a float64) error {
+func (c *Context) FillFramebuffer(r, g, b, a float32) error {
 	gl := c.gl
-	gl.ClearColor(float32(r), float32(g), float32(b), float32(a))
+	gl.ClearColor(r, g, b, a)
 	gl.Clear(mgl.COLOR_BUFFER_BIT)
 	return nil
 }