func (r Region) setClipPlanes() {
eqs[0][0], eqs[0][1], eqs[0][2], eqs[0][3] = 1, 0, 0, -gl.Double(r.X)
eqs[1][0], eqs[1][1], eqs[1][2], eqs[1][3] = -1, 0, 0, gl.Double(r.X+r.Dx)
eqs[2][0], eqs[2][1], eqs[2][2], eqs[2][3] = 0, 1, 0, -gl.Double(r.Y)
eqs[3][0], eqs[3][1], eqs[3][2], eqs[3][3] = 0, -1, 0, gl.Double(r.Y+r.Dy)
gl.ClipPlane(gl.CLIP_PLANE0, &eqs[0][0])
gl.ClipPlane(gl.CLIP_PLANE1, &eqs[1][0])
gl.ClipPlane(gl.CLIP_PLANE2, &eqs[2][0])
gl.ClipPlane(gl.CLIP_PLANE3, &eqs[3][0])
}
func (tm *ThunderMenu) Draw(region Region, style StyleStack) {
// Set clip planes
gl.PushAttrib(gl.TRANSFORM_BIT)
defer gl.PopAttrib()
var eqs [4][4]gl.Double
eqs[0][0], eqs[0][1], eqs[0][2], eqs[0][3] = 1, 0, 0, -gl.Double(region.X)
eqs[1][0], eqs[1][1], eqs[1][2], eqs[1][3] = -1, 0, 0, gl.Double(region.X+region.Dx)
eqs[2][0], eqs[2][1], eqs[2][2], eqs[2][3] = 0, 1, 0, -gl.Double(region.Y)
eqs[3][0], eqs[3][1], eqs[3][2], eqs[3][3] = 0, -1, 0, gl.Double(region.Y+region.Dy)
gl.Enable(gl.CLIP_PLANE0)
gl.Enable(gl.CLIP_PLANE1)
gl.Enable(gl.CLIP_PLANE2)
gl.Enable(gl.CLIP_PLANE3)
gl.ClipPlane(gl.CLIP_PLANE0, &eqs[0][0])
gl.ClipPlane(gl.CLIP_PLANE1, &eqs[1][0])
gl.ClipPlane(gl.CLIP_PLANE2, &eqs[2][0])
gl.ClipPlane(gl.CLIP_PLANE3, &eqs[3][0])
var start, end int
if tm.delta <= 0 {
start = tm.current + int(math.Floor(tm.delta))
end = tm.current
region.X += int(float64(region.Dx) * (float64(start-tm.current) - tm.delta))
} else {
start = tm.current
end = tm.current + int(math.Ceil(tm.delta))
region.X += int(float64(region.Dx) * (float64(end-tm.current) - tm.delta - math.Floor(tm.delta) - 1))
}
var offset linear.Vec2
offset.X = (float64(tm.current) + tm.delta) * float64(region.Dx)
for i := start; i <= end; i++ {
style.PushStyle(map[string]interface{}{"offset": offset})
tm.Subs[tm.menuStack[i]].Draw(region, style)
style.Pop()
region.X += region.Dx
}
}