From 9424579c7514aaaebe9d90a354929d52aed57f48 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C5=99emysl=20Janouch?= <p@janouch.name>
Date: Thu, 23 Aug 2018 03:37:43 +0200
Subject: [PATCH] xgb-render: cleanup, tolerable glyph placement

---
 prototypes/xgb-xrender.go | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/prototypes/xgb-xrender.go b/prototypes/xgb-xrender.go
index 5fbdf36..dba6687 100644
--- a/prototypes/xgb-xrender.go
+++ b/prototypes/xgb-xrender.go
@@ -53,6 +53,8 @@ type xgbCookie interface{ Check() error }
 
 // TODO: We actually need a higher-level function that also keeps track of
 // and loads glyphs into the X server.
+// TODO: We also need a way to use kerning tables with this, inserting/removing
+// advance pixels between neighboring characters.
 
 // compositeString makes an appropriate render.CompositeGlyphs request,
 // assuming that glyphs equal Unicode codepoints.
@@ -109,8 +111,6 @@ func compositeString(c *xgb.Conn, op byte, src, dst render.Picture,
 	}
 }
 
-// ---
-
 func main() {
 	X, err := xgb.NewConn()
 	if err != nil {
@@ -224,12 +224,15 @@ func main() {
 		log.Fatalln(err)
 	}
 
+	// LCD subpixel rendering isn't supported. :(
 	opts := &truetype.Options{
 		Size:    9,
 		DPI:     96, // TODO: Take this from the screen or monitor.
 		Hinting: font.HintingFull,
 	}
 	face := truetype.NewFace(f, opts)
+	bounds := f.Bounds(fixed.Int26_6(opts.Size * float64(opts.DPI) *
+		(64.0 / 72.0)))
 
 	var rgbFormat render.Pictformat
 	for _, pf := range pformats.Formats {
@@ -249,17 +252,18 @@ func main() {
 	// NOTE: A depth of 24 will not work, the server always rejects it.
 	_ = render.CreateGlyphSet(X, gsid, rgbFormat)
 
-	//bounds := f.Bounds(c.PointToFixed(opts.Size))
-	//log.Println("+%v", bounds)
-
 	// 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(0, 0, 36, 36))
-	//nrgb.Bounds()
+	nrgb := image.NewRGBA(image.Rect(
+		+bounds.Min.X.Floor(),
+		-bounds.Min.Y.Floor(),
+		+bounds.Max.X.Ceil(),
+		-bounds.Max.Y.Ceil(),
+	))
 
 	for r := rune(32); r < 128; r++ {
 		dr, mask, maskp, advance, ok := face.Glyph(
-			fixed.P(0, 18) /* subpixel destination location */, r)
+			fixed.P(0, 0) /* subpixel destination location */, r)
 		if !ok {
 			log.Println("skip")
 			continue
@@ -270,16 +274,15 @@ func main() {
 		}
 
 		draw.Draw(nrgb, dr, mask, maskp, draw.Src)
-		_ = advance
 
 		_ = render.AddGlyphs(X, gsid, 1, []uint32{uint32(r)},
 			[]render.Glyphinfo{{
-				Width:  uint16(36),
-				Height: uint16(36),
-				X:      int16(18),
-				Y:      int16(18),
-				XOff:   int16(18),
-				YOff:   0,
+				Width:  uint16(nrgb.Rect.Size().X),
+				Height: uint16(nrgb.Rect.Size().Y),
+				X:      int16(-bounds.Min.X.Floor()),
+				Y:      int16(+bounds.Max.Y.Ceil()),
+				XOff:   int16(advance.Ceil()),
+				YOff:   int16(0),
 			}}, []byte(nrgb.Pix))
 	}
 
@@ -350,6 +353,9 @@ func main() {
 		_ = compositeString(X, render.PictOpOver, whiteid, pid,
 			0 /* TODO: mask Pictureformat? */, gsid, 0, 0, 100, 100,
 			fmt.Sprintf("%#06x - %#06x", start, end))
+		_ = compositeString(X, render.PictOpOver, whiteid, pid,
+			0 /* TODO: mask Pictureformat? */, gsid, 0, 0, 100, 150,
+			"The quick brown fox jumps over the lazy dog.")
 	}
 
 	for {