xgb-render: give up on composite alpha

prototypes/xgb-xrender.go

@@ -234,13 +234,10 @@ func main() {
 	bounds := f.Bounds(fixed.Int26_6(opts.Size * float64(opts.DPI) *
 		(64.0 / 72.0)))
 
-	var rgbFormat render.Pictformat
+	var alphaFormat render.Pictformat
 	for _, pf := range pformats.Formats {
-		// Hopefully. Might want to check ARGB/BGRA.
-		if pf.Depth == 32 && pf.Direct.AlphaMask != 0 {
-			rgbFormat = pf.Id
-			log.Printf("%+v\n", pf)
-			break
+		if pf.Depth == 8 && pf.Direct.AlphaMask == 0xff {
+			alphaFormat = pf.Id
 		}
 	}
 
@@ -250,11 +247,12 @@ func main() {
 	}
 
 	// NOTE: A depth of 24 will not work, the server always rejects it.
-	_ = render.CreateGlyphSet(X, gsid, rgbFormat)
+	// Composite alpha doesn't make sense since golang/freetype can't use it.
+	_ = render.CreateGlyphSet(X, gsid, alphaFormat)
 
-	// TODO: Seems like we want to use NRGBA. Or RGBA if the A is always 1.
-	// Or implement our own image.Image for direct gamma-corrected RGB!
-	nrgb := image.NewRGBA(image.Rect(
+	// NOTE: We could do gamma post-correction in higher precision if we
+	// implemented our own clone of the image.Image implementation.
+	nrgb := image.NewGray(image.Rect(
 		+bounds.Min.X.Floor(),
 		-bounds.Min.Y.Floor(),
 		+bounds.Max.X.Ceil(),