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added a clip function to clip to a polygon (doesn't work with save/restore yet)

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Thomas Friedel 2018-01-30 18:32:35 +01:00
parent 1727f47a6f
commit 4a0b551a93
2 changed files with 54 additions and 4 deletions
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2
canvas.go
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@ -129,6 +129,8 @@ func LoadGL(glimpl GL) (err error) {
gli.Enable(gl_BLEND)
gli.BlendFunc(gl_SRC_ALPHA, gl_ONE_MINUS_SRC_ALPHA)
gli.Enable(gl_STENCIL_TEST)
gli.StencilFunc(gl_EQUAL, 1, 0x00)
return
}

56
paths.go
View file

@ -61,11 +61,10 @@ func (cv *Canvas) Stroke() {
cv.activate()
gli.Enable(gl_STENCIL_TEST)
gli.ColorMask(false, false, false, false)
gli.StencilFunc(gl_ALWAYS, 1, 0xFF)
gli.StencilOp(gl_KEEP, gl_KEEP, gl_REPLACE)
gli.StencilMask(0xFF)
gli.StencilMask(0x01)
gli.Clear(gl_STENCIL_BUFFER_BIT)
gli.UseProgram(sr.id)
@ -106,13 +105,16 @@ func (cv *Canvas) Stroke() {
gli.ColorMask(true, true, true, true)
gli.StencilFunc(gl_EQUAL, 1, 0xFF)
gli.StencilMask(0)
gli.StencilMask(0xFF)
gli.DrawArrays(gl_TRIANGLE_FAN, 0, 6)
gli.DisableVertexAttribArray(sr.vertex)
gli.Disable(gl_STENCIL_TEST)
gli.ColorMask(true, true, true, true)
gli.StencilOp(gl_KEEP, gl_KEEP, gl_KEEP)
gli.StencilMask(0xFF)
gli.StencilFunc(gl_EQUAL, 0, 0xFF)
}
func (cv *Canvas) Fill() {
@ -129,6 +131,44 @@ func (cv *Canvas) Fill() {
gli.BindBuffer(gl_ARRAY_BUFFER, buf)
var buf [1000]float32
tris := buf[:0]
tris = append(tris)
tris = triangulatePath(cv.path, tris)
total := len(tris)
for i := 0; i < total; i += 2 {
x, y := tris[i], tris[i+1]
tris[i], tris[i+1] = cv.ptToGL(x, y)
}
gli.BufferData(gl_ARRAY_BUFFER, len(tris)*4, unsafe.Pointer(&tris[0]), gl_STREAM_DRAW)
gli.VertexAttribPointer(sr.vertex, 2, gl_FLOAT, false, 0, nil)
gli.DrawArrays(gl_TRIANGLES, 0, int32(len(tris)/2))
gli.DisableVertexAttribArray(sr.vertex)
}
func (cv *Canvas) Clip() {
if len(cv.path) < 3 {
return
}
cv.activate()
gli.ColorMask(false, false, false, false)
gli.StencilFunc(gl_ALWAYS, 2, 0xFF)
gli.StencilOp(gl_KEEP, gl_KEEP, gl_REPLACE)
gli.StencilMask(0x02)
gli.Clear(gl_STENCIL_BUFFER_BIT)
gli.UseProgram(sr.id)
f := cv.state.fill
gli.Uniform4f(sr.color, f.r, f.g, f.b, f.a)
gli.EnableVertexAttribArray(sr.vertex)
gli.BindBuffer(gl_ARRAY_BUFFER, buf)
var buf [1000]float32
tris := buf[:0]
tris = append(tris, -1, -1, -1, 1, 1, 1, -1, -1, 1, 1, 1, -1)
@ -142,7 +182,15 @@ func (cv *Canvas) Fill() {
gli.BufferData(gl_ARRAY_BUFFER, len(tris)*4, unsafe.Pointer(&tris[0]), gl_STREAM_DRAW)
gli.VertexAttribPointer(sr.vertex, 2, gl_FLOAT, false, 0, nil)
gli.DrawArrays(gl_TRIANGLES, 0, 6)
gli.StencilFunc(gl_ALWAYS, 0, 0xFF)
gli.DrawArrays(gl_TRIANGLES, 6, int32(len(tris)/2-6))
gli.DisableVertexAttribArray(sr.vertex)
gli.ColorMask(true, true, true, true)
gli.StencilOp(gl_KEEP, gl_KEEP, gl_KEEP)
gli.StencilMask(0xFF)
gli.StencilFunc(gl_EQUAL, 0, 0xFF)
}