graphics: Refactoring: Simplify NextPowerOf2Int

imageparts.go

@@ -89,8 +89,8 @@ func (t *textureQuads) vertices() []uint8 {
 	vertices := make([]uint8, l*size)
 	p := t.parts
 	w, h := t.width, t.height
-	width2p := int(graphics.NextPowerOf2Int32(int32(w)))
-	height2p := int(graphics.NextPowerOf2Int32(int32(h)))
+	width2p := graphics.NextPowerOf2Int(w)
+	height2p := graphics.NextPowerOf2Int(h)
 	n := 0
 	for i := 0; i < l; i++ {
 		dx0, dy0, dx1, dy1 := p.Dst(i)

internal/graphics/command.go

@@ -260,8 +260,8 @@ func adjustImageForTexture(img *image.RGBA) *image.RGBA {
 	adjustedImageBounds := image.Rectangle{
 		image.ZP,
 		image.Point{
-			int(NextPowerOf2Int32(int32(width))),
-			int(NextPowerOf2Int32(int32(height))),
+			NextPowerOf2Int(width),
+			NextPowerOf2Int(height),
 		},
 	}
 	if img.Bounds() == adjustedImageBounds {
@@ -309,8 +309,8 @@ type newImageCommand struct {
 }
 
 func (c *newImageCommand) Exec(context *opengl.Context, indexOffsetInBytes int) error {
-	w := int(NextPowerOf2Int32(int32(c.width)))
-	h := int(NextPowerOf2Int32(int32(c.height)))
+	w := NextPowerOf2Int(c.width)
+	h := NextPowerOf2Int(c.height)
 	if w < 1 {
 		return errors.New("graphics: width must be equal or more than 1.")
 	}

internal/graphics/math.go

@@ -14,12 +14,13 @@
 
 package graphics
 
-func NextPowerOf2Int32(x int32) int32 {
-	x -= 1
-	x |= (x >> 1)
-	x |= (x >> 2)
-	x |= (x >> 4)
-	x |= (x >> 8)
-	x |= (x >> 16)
-	return x + 1
+func NextPowerOf2Int(x int) int {
+	if x <= 0 {
+		panic("x must be positive")
+	}
+	r := 1
+	for r < x {
+		r <<= 1
+	}
+	return r
 }

internal/graphics/math_test.go

@@ -21,8 +21,8 @@ import (
 
 func TestNextPowerOf2(t *testing.T) {
 	testCases := []struct {
-		expected int32
-		arg      int32
+		expected int
+		arg      int
 	}{
 		{256, 255},
 		{256, 256},
@@ -30,7 +30,7 @@ func TestNextPowerOf2(t *testing.T) {
 	}
 
 	for _, testCase := range testCases {
-		got := NextPowerOf2Int32(testCase.arg)
+		got := NextPowerOf2Int(testCase.arg)
 		wanted := testCase.expected
 		if wanted != got {
 			t.Errorf("Clp(%d) = %d, wanted %d", testCase.arg, got, wanted)