/
scroll.go
54 lines (44 loc) · 921 Bytes
/
scroll.go
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package main
import (
"go.vktec.org.uk/vtk"
"math"
)
func main() {
root, err := vtk.New()
if err != nil {
panic(err)
}
defer root.Destroy()
win, err := root.NewWindow("vtk scroll example", 0, 0, 800, 600)
if err != nil {
panic(err)
}
defer win.Destroy()
cr := win.Cairo()
angle := 0.0
win.SetEventHandler(vtk.Close, func(ev vtk.Event) {
win.Close()
})
win.SetEventHandler(vtk.Draw, func(ev vtk.Event) {
width, height := win.Size()
w, h := float64(width), float64(height)
cr.Translate(0, 0)
cr.Rotate(0)
cr.Rectangle(0, 0, w, h)
cr.SetSourceRGB(0, 0, 0)
cr.Fill()
cr.Translate(w/2, h/2)
cr.Rotate(angle)
cr.MoveTo(-w/2, -h/2)
cr.LineTo(w/2, h/2)
cr.SetSourceRGB(1, 1, 1)
cr.SetLineWidth(2)
cr.Stroke()
})
win.SetEventHandler(vtk.Scroll, func(ev vtk.Event) {
s := ev.(vtk.ScrollEvent)
angle -= s.Amount() / (8 * math.Pi)
win.Redraw()
})
win.Mainloop()
}