draw optimizations

client/world/drawer.go

@@ -290,19 +290,26 @@ func (d *GGDrawer) ClearAllTo(bg color.Color) {
 		panic("GGDrawer.ClearAllTo: backing image is not *image.RGBA")
 	}
 
-	r, g, b, a := bg.RGBA()
-	// Convert from 16-bit range to 8-bit.
-	R := byte(r >> 8)
-	G := byte(g >> 8)
-	B := byte(b >> 8)
-	A := byte(a >> 8)
+	R, G, B, A := rgba8(bg)
 
-	p := img.Pix
-	for i := 0; i+3 < len(p); i += 4 {
-		p[i+0] = R
-		p[i+1] = G
-		p[i+2] = B
-		p[i+3] = A
+	// Prepare one full scanline once.
+	w := img.Bounds().Dx()
+	if w <= 0 {
+		return
+	}
+	line := make([]byte, w*4)
+	for i := 0; i < len(line); i += 4 {
+		line[i+0] = R
+		line[i+1] = G
+		line[i+2] = B
+		line[i+3] = A
+	}
+
+	// Copy scanline into each row (fast memmove).
+	h := img.Bounds().Dy()
+	for y := 0; y < h; y++ {
+		off := y * img.Stride
+		copy(img.Pix[off:off+w*4], line)
 	}
 }
 
@@ -316,33 +323,40 @@ func (d *GGDrawer) ClearRectTo(x, y, w, h int, bg color.Color) {
 		panic("GGDrawer.ClearRectTo: backing image is not *image.RGBA")
 	}
 
-	bounds := img.Bounds()
-	x0 := max(x, bounds.Min.X)
-	y0 := max(y, bounds.Min.Y)
-	x1 := min(x+w, bounds.Max.X)
-	y1 := min(y+h, bounds.Max.Y)
+	b := img.Bounds()
+	x0 := max(x, b.Min.X)
+	y0 := max(y, b.Min.Y)
+	x1 := min(x+w, b.Max.X)
+	y1 := min(y+h, b.Max.Y)
 	if x0 >= x1 || y0 >= y1 {
 		return
 	}
 
-	r, g, b, a := bg.RGBA()
-	R := byte(r >> 8)
-	G := byte(g >> 8)
-	B := byte(b >> 8)
-	A := byte(a >> 8)
+	R, G, B, A := rgba8(bg)
+
+	rowPx := x1 - x0
+	rowBytes := rowPx * 4
+
+	// Build one row once for this rect width.
+	line := make([]byte, rowBytes)
+	for i := 0; i < rowBytes; i += 4 {
+		line[i+0] = R
+		line[i+1] = G
+		line[i+2] = B
+		line[i+3] = A
+	}
 
-	rowBytes := (x1 - x0) * 4
 	for yy := y0; yy < y1; yy++ {
 		off := yy*img.Stride + x0*4
-		for i := 0; i < rowBytes; i += 4 {
-			img.Pix[off+i+0] = R
-			img.Pix[off+i+1] = G
-			img.Pix[off+i+2] = B
-			img.Pix[off+i+3] = A
-		}
+		copy(img.Pix[off:off+rowBytes], line)
 	}
 }
 
+func rgba8(c color.Color) (R, G, B, A byte) {
+	r, g, b, a := c.RGBA()
+	return byte(r >> 8), byte(g >> 8), byte(b >> 8), byte(a >> 8)
+}
+
 func (g *GGDrawer) DrawImage(img image.Image, x, y int) {
 	g.DC.DrawImage(img, x, y)
 }