142 lines
3.3 KiB
Go
142 lines
3.3 KiB
Go
package main
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import (
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"github.com/BurntSushi/xgb"
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"github.com/BurntSushi/xgb/render"
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"github.com/BurntSushi/xgb/xproto"
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"log"
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)
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func F64ToFixed(f float64) render.Fixed { return render.Fixed(f * 65536) }
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func FixedToF64(f render.Fixed) float64 { return float64(f) / 65536 }
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func main() {
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X, err := xgb.NewConn()
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if err != nil {
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log.Fatalln(err)
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}
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if err := render.Init(X); err != nil {
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log.Fatalln(err)
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}
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setup := xproto.Setup(X)
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screen := setup.DefaultScreen(X)
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visual, depth := screen.RootVisual, screen.RootDepth
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if depth < 24 {
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log.Fatalln("need more colors")
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}
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wid, err := xproto.NewWindowId(X)
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if err != nil {
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log.Fatalln(err)
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}
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_ = xproto.CreateWindow(X, depth, wid, screen.Root,
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0, 0, 500, 500, 0, xproto.WindowClassInputOutput,
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visual, xproto.CwBackPixel|xproto.CwEventMask,
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[]uint32{0xffffffff, xproto.EventMaskButtonPress |
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xproto.EventMaskButtonMotion | xproto.EventMaskButtonRelease |
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xproto.EventMaskStructureNotify})
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title := []byte("Draw")
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_ = xproto.ChangeProperty(X, xproto.PropModeReplace, wid, xproto.AtomWmName,
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xproto.AtomString, 8, uint32(len(title)), title)
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_ = xproto.MapWindow(X, wid)
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pformats, err := render.QueryPictFormats(X).Reply()
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if err != nil {
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log.Fatalln(err)
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}
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var pformat render.Pictformat
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for _, pd := range pformats.Screens[X.DefaultScreen].Depths {
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for _, pv := range pd.Visuals {
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if pv.Visual == visual {
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pformat = pv.Format
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}
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}
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}
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pid, err := render.NewPictureId(X)
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if err != nil {
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log.Fatalln(err)
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}
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render.CreatePicture(X, pid, xproto.Drawable(wid), pformat, 0, []uint32{})
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// Brush shape.
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brushid, err := render.NewPictureId(X)
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if err != nil {
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log.Fatalln(err)
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}
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cFull := render.Color{0xffff, 0xffff, 0xffff, 0xffff}
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cTrans := render.Color{0xffff, 0xffff, 0xffff, 0}
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_ = render.CreateRadialGradient(X, brushid,
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render.Pointfix{F64ToFixed(50), F64ToFixed(50)},
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render.Pointfix{F64ToFixed(50), F64ToFixed(50)},
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F64ToFixed(0),
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F64ToFixed(50),
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2, []render.Fixed{F64ToFixed(0), F64ToFixed(1)},
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[]render.Color{cFull, cTrans})
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// Brush color.
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colorid, err := render.NewPictureId(X)
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if err != nil {
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log.Fatalln(err)
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}
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_ = render.CreateSolidFill(X, colorid, render.Color{
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Red: 0xcccc,
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Green: 0xaaaa,
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Blue: 0x8888,
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Alpha: 0xffff,
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})
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// Unfortunately, XRender won't give us any /blending operators/, only
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// providing basic Porter-Duff ones with useless disjoint/conjoint variants,
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// but we need the "lighten" operator to draw brush strokes properly.
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//
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// https://www.cairographics.org/operators/
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// http://ssp.impulsetrain.com/porterduff.html
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printAt := func(x, y int16) {
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_ = render.Composite(X, render.PictOpOver,
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colorid, brushid, pid,
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0, 0, 0, 0, x-50, y-50, 100, 100)
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}
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drawing := false
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for {
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ev, xerr := X.WaitForEvent()
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if xerr != nil {
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log.Printf("Error: %s\n", xerr)
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return
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}
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if ev == nil {
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return
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}
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log.Printf("Event: %s\n", ev)
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switch e := ev.(type) {
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case xproto.UnmapNotifyEvent:
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return
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case xproto.ButtonPressEvent:
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if e.Detail == xproto.ButtonIndex1 {
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drawing = true
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printAt(e.EventX, e.EventY)
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}
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case xproto.MotionNotifyEvent:
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if drawing {
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printAt(e.EventX, e.EventY)
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}
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case xproto.ButtonReleaseEvent:
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if e.Detail == xproto.ButtonIndex1 {
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drawing = false
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}
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}
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}
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}
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