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-rw-r--r--prototypes/xgb-draw.go141
1 files changed, 141 insertions, 0 deletions
diff --git a/prototypes/xgb-draw.go b/prototypes/xgb-draw.go
new file mode 100644
index 0000000..540783b
--- /dev/null
+++ b/prototypes/xgb-draw.go
@@ -0,0 +1,141 @@
+package main
+
+import (
+ "github.com/BurntSushi/xgb"
+ "github.com/BurntSushi/xgb/render"
+ "github.com/BurntSushi/xgb/xproto"
+ "log"
+)
+
+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)
+
+ visual, depth := screen.RootVisual, screen.RootDepth
+ if depth < 24 {
+ log.Fatalln("need more colors")
+ }
+
+ wid, err := xproto.NewWindowId(X)
+ if err != nil {
+ log.Fatalln(err)
+ }
+
+ _ = xproto.CreateWindow(X, depth, wid, screen.Root,
+ 0, 0, 500, 500, 0, xproto.WindowClassInputOutput,
+ visual, xproto.CwBackPixel|xproto.CwEventMask,
+ []uint32{0xffffffff, xproto.EventMaskButtonPress |
+ xproto.EventMaskButtonMotion | xproto.EventMaskButtonRelease |
+ xproto.EventMaskStructureNotify})
+
+ title := []byte("Draw")
+ _ = 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)
+ }
+
+ var pformat render.Pictformat
+ for _, pd := range pformats.Screens[X.DefaultScreen].Depths {
+ for _, pv := range pd.Visuals {
+ if pv.Visual == visual {
+ pformat = pv.Format
+ }
+ }
+ }
+
+ pid, err := render.NewPictureId(X)
+ if err != nil {
+ log.Fatalln(err)
+ }
+ render.CreatePicture(X, pid, xproto.Drawable(wid), pformat, 0, []uint32{})
+
+ // Brush shape.
+ brushid, err := render.NewPictureId(X)
+ if err != nil {
+ log.Fatalln(err)
+ }
+
+ cFull := render.Color{0xffff, 0xffff, 0xffff, 0xffff}
+ cTrans := render.Color{0xffff, 0xffff, 0xffff, 0}
+ _ = render.CreateRadialGradient(X, brushid,
+ render.Pointfix{F64ToFixed(50), F64ToFixed(50)},
+ render.Pointfix{F64ToFixed(50), F64ToFixed(50)},
+ F64ToFixed(0),
+ F64ToFixed(50),
+ 2, []render.Fixed{F64ToFixed(0), F64ToFixed(1)},
+ []render.Color{cFull, cTrans})
+
+ // Brush color.
+ colorid, err := render.NewPictureId(X)
+ if err != nil {
+ log.Fatalln(err)
+ }
+ _ = render.CreateSolidFill(X, colorid, render.Color{
+ Red: 0xcccc,
+ Green: 0xaaaa,
+ Blue: 0x8888,
+ Alpha: 0xffff,
+ })
+
+ // Unfortunately, XRender won't give us any /blending operators/, only
+ // providing basic Porter-Duff ones with useless disjoint/conjoint variants,
+ // but we need the "lighten" operator to draw brush strokes properly.
+ //
+ // https://www.cairographics.org/operators/
+ // http://ssp.impulsetrain.com/porterduff.html
+ printAt := func(x, y int16) {
+ _ = render.Composite(X, render.PictOpOver,
+ colorid, brushid, pid,
+ 0, 0, 0, 0, x-50, y-50, 100, 100)
+ }
+
+ drawing := false
+ 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.ButtonPressEvent:
+ if e.Detail == xproto.ButtonIndex1 {
+ drawing = true
+ printAt(e.EventX, e.EventY)
+ }
+
+ case xproto.MotionNotifyEvent:
+ if drawing {
+ printAt(e.EventX, e.EventY)
+ }
+
+ case xproto.ButtonReleaseEvent:
+ if e.Detail == xproto.ButtonIndex1 {
+ drawing = false
+ }
+ }
+ }
+}