62 lines
1.5 KiB
Go
62 lines
1.5 KiB
Go
package goglbackend
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import (
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"unsafe"
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"github.com/go-gl/gl/v3.2-core/gl"
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)
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func (b *GoGLBackend) ClearClip() {
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gl.StencilMask(0xFF)
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gl.Clear(gl.STENCIL_BUFFER_BIT)
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}
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func (b *GoGLBackend) Clip(pts [][2]float64) {
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b.ptsBuf = b.ptsBuf[:0]
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b.ptsBuf = append(b.ptsBuf,
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0, 0,
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0, float32(b.fh),
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float32(b.fw), float32(b.fh),
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float32(b.fw), 0)
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for _, pt := range pts {
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b.ptsBuf = append(b.ptsBuf, float32(pt[0]), float32(pt[1]))
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}
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mode := uint32(gl.TRIANGLES)
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if len(pts) == 4 {
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mode = gl.TRIANGLE_FAN
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}
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gl.BindBuffer(gl.ARRAY_BUFFER, b.buf)
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gl.BufferData(gl.ARRAY_BUFFER, len(b.ptsBuf)*4, unsafe.Pointer(&b.ptsBuf[0]), gl.STREAM_DRAW)
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gl.VertexAttribPointer(b.sr.Vertex, 2, gl.FLOAT, false, 0, nil)
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gl.UseProgram(b.sr.ID)
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gl.Uniform4f(b.sr.Color, 1, 1, 1, 1)
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gl.Uniform2f(b.sr.CanvasSize, float32(b.fw), float32(b.fh))
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gl.EnableVertexAttribArray(b.sr.Vertex)
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gl.ColorMask(false, false, false, false)
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gl.StencilMask(0x04)
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gl.StencilFunc(gl.ALWAYS, 4, 0x04)
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gl.StencilOp(gl.REPLACE, gl.REPLACE, gl.REPLACE)
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gl.DrawArrays(mode, 4, int32(len(pts)))
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gl.StencilMask(0x02)
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gl.StencilFunc(gl.EQUAL, 0, 0x06)
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gl.StencilOp(gl.KEEP, gl.INVERT, gl.INVERT)
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gl.DrawArrays(gl.TRIANGLE_FAN, 0, 4)
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gl.StencilMask(0x04)
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gl.StencilFunc(gl.ALWAYS, 0, 0x04)
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gl.StencilOp(gl.ZERO, gl.ZERO, gl.ZERO)
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gl.DrawArrays(gl.TRIANGLE_FAN, 0, 4)
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gl.DisableVertexAttribArray(b.sr.Vertex)
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gl.ColorMask(true, true, true, true)
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gl.StencilOp(gl.KEEP, gl.KEEP, gl.KEEP)
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gl.StencilMask(0xFF)
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gl.StencilFunc(gl.EQUAL, 0, 0xFF)
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}
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