xgb-xrender: add a basic demo for XRender

So far just a conversion of xgb-window.go.

prototypes/xgb-xrender.go

@@ -0,0 +1,176 @@
+package main
+
+import (
+	"github.com/BurntSushi/xgb"
+	"github.com/BurntSushi/xgb/render"
+	"github.com/BurntSushi/xgb/xproto"
+	"log"
+	"math/rand"
+)
+
+func F64ToFixed(f float64) render.Fixed { return render.Fixed(f * 65536) }
+func FixedToF64(f render.Fixed) float64 { return float64(f) / 65536 }
+
+func main() {
+	X, err := xgb.NewConn()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	if err := render.Init(X); err != nil {
+		log.Fatalln(err)
+	}
+
+	setup := xproto.Setup(X)
+	screen := setup.DefaultScreen(X)
+
+	var visual xproto.Visualid
+	var depth byte
+	for _, i := range screen.AllowedDepths {
+		if i.Depth == 32 {
+			// TODO: Could/should check other parameters.
+			for _, v := range i.Visuals {
+				if v.Class == xproto.VisualClassTrueColor {
+					visual = v.VisualId
+					depth = i.Depth
+					break
+				}
+			}
+		}
+	}
+	if visual == 0 {
+		log.Fatalln("cannot find an RGBA TrueColor visual")
+	}
+
+	mid, err := xproto.NewColormapId(X)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	_ = xproto.CreateColormap(
+		X, xproto.ColormapAllocNone, mid, screen.Root, visual)
+
+	wid, err := xproto.NewWindowId(X)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// Border pixel and colormap are required when depth differs from parent.
+	_ = xproto.CreateWindow(X, depth, wid, screen.Root,
+		0, 0, 500, 500, 0, xproto.WindowClassInputOutput,
+		visual, xproto.CwBorderPixel|xproto.CwColormap,
+		[]uint32{0, uint32(mid)})
+
+	// This could be included in CreateWindow parameters.
+	_ = xproto.ChangeWindowAttributes(X, wid,
+		xproto.CwBackPixel|xproto.CwEventMask, []uint32{0x80808080,
+			xproto.EventMaskStructureNotify | xproto.EventMaskKeyPress |
+				xproto.EventMaskExposure})
+
+	title := []byte("Gradient")
+	_ = xproto.ChangeProperty(X, xproto.PropModeReplace, wid, xproto.AtomWmName,
+		xproto.AtomString, 8, uint32(len(title)), title)
+
+	_ = xproto.MapWindow(X, wid)
+
+	pformats, err := render.QueryPictFormats(X).Reply()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	// Similar to XRenderFindVisualFormat.
+	// The DefaultScreen is almost certain to be zero.
+	var pformat render.Pictformat
+	for _, pd := range pformats.Screens[X.DefaultScreen].Depths {
+		// This check seems to be slightly extraneous.
+		if pd.Depth != depth {
+			continue
+		}
+		for _, pv := range pd.Visuals {
+			if pv.Visual == visual {
+				pformat = pv.Format
+			}
+		}
+	}
+
+	// ...or just scan through pformats.Formats and look for matches, which is
+	// what XRenderFindStandardFormat in Xlib does as well as exp/shiny.
+
+	pid, err := render.NewPictureId(X)
+	if err != nil {
+		log.Fatalln(err)
+	}
+	render.CreatePicture(X, pid, xproto.Drawable(wid), pformat, 0, []uint32{})
+
+	// Reserve an ID for the gradient.
+	gid, err := render.NewPictureId(X)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	var from, to render.Color
+	recolor := func() {
+		start := rand.Uint32() & 0xffffff
+		from = render.Color{
+			Red:   0x101 * uint16((start>>16)&0xff),
+			Green: 0x101 * uint16((start>>8)&0xff),
+			Blue:  0x101 * uint16(start&0xff),
+			Alpha: 0xffff,
+		}
+
+		end := rand.Uint32() & 0xffffff
+		to = render.Color{
+			Red:   0x101 * uint16((end>>16)&0xff),
+			Green: 0x101 * uint16((end>>8)&0xff),
+			Blue:  0x101 * uint16(end&0xff),
+			Alpha: 0xffff,
+		}
+	}
+
+	var w, h uint16
+	gradient := func() {
+		if w < 100 || h < 100 {
+			return
+		}
+
+		_ = render.CreateLinearGradient(X, gid,
+			render.Pointfix{F64ToFixed(0), F64ToFixed(0)},
+			render.Pointfix{F64ToFixed(0), F64ToFixed(float64(h) - 100)},
+			2, []render.Fixed{F64ToFixed(0), F64ToFixed(1)},
+			[]render.Color{from, to})
+
+		_ = render.Composite(X, render.PictOpSrc, gid, render.PictureNone, pid,
+			0, 0, 0, 0, 50, 50, w-100, h-100)
+
+		_ = render.FreePicture(X, gid)
+	}
+
+	for {
+		ev, xerr := X.WaitForEvent()
+		if xerr != nil {
+			log.Printf("Error: %s\n", xerr)
+			return
+		}
+		if ev == nil {
+			return
+		}
+
+		log.Printf("Event: %s\n", ev)
+		switch e := ev.(type) {
+		case xproto.UnmapNotifyEvent:
+			return
+
+		case xproto.ConfigureNotifyEvent:
+			w, h = e.Width, e.Height
+			recolor()
+
+		case xproto.KeyPressEvent:
+			recolor()
+			gradient()
+
+		case xproto.ExposeEvent:
+			gradient()
+		}
+	}
+
+}