mirror of
https://git.sr.ht/~eliasnaur/gio
synced 2026-07-01 15:45:38 +00:00
Elias Naur
593 lines
16 KiB
Go
593 lines
16 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package gpu
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// GPU accelerated path drawing using the algorithms from
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// Pathfinder (https://github.com/pcwalton/pathfinder).
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import (
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"image"
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"unsafe"
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"gioui.org/ui/app/internal/gl"
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"gioui.org/ui/f32"
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"gioui.org/ui/internal/path"
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)
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type pather struct {
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ctx *context
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viewport image.Point
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stenciler *stenciler
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coverer *coverer
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}
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type coverer struct {
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ctx *context
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prog [2]gl.Program
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vars [2]struct {
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z gl.Uniform
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uScale, uOffset gl.Uniform
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uUVScale, uUVOffset gl.Uniform
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uCoverUVScale, uCoverUVOffset gl.Uniform
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uColor gl.Uniform
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}
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}
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type stenciler struct {
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ctx *context
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defFBO gl.Framebuffer
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indexBufQuads int
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prog gl.Program
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iprog gl.Program
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fbos fboSet
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intersections fboSet
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uScale, uOffset gl.Uniform
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uPathOffset gl.Uniform
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uIntersectUVOffset gl.Uniform
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uIntersectUVScale gl.Uniform
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indexBuf gl.Buffer
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areaLUT gl.Texture
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}
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type fboSet struct {
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fbos []stencilFBO
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}
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type stencilFBO struct {
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size image.Point
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fbo gl.Framebuffer
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tex gl.Texture
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}
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type pathData struct {
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ncurves int
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data gl.Buffer
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}
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var (
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pathAttribs = []string{"corner", "maxy", "from", "ctrl", "to"}
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attribPathCorner gl.Attrib = 0
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attribPathMaxY gl.Attrib = 1
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attribPathFrom gl.Attrib = 2
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attribPathCtrl gl.Attrib = 3
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attribPathTo gl.Attrib = 4
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intersectAttribs = []string{"pos", "uv"}
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)
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func newPather(ctx *context) *pather {
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return &pather{
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ctx: ctx,
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stenciler: newStenciler(ctx),
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coverer: newCoverer(ctx),
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}
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}
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func newCoverer(ctx *context) *coverer {
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prog, err := createColorPrograms(ctx, coverVSrc, coverFSrc)
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if err != nil {
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panic(err)
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}
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c := &coverer{
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ctx: ctx,
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prog: prog,
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}
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for i, prog := range prog {
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ctx.UseProgram(prog)
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switch materialType(i) {
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case materialTexture:
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uTex := gl.GetUniformLocation(ctx.Functions, prog, "tex")
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ctx.Uniform1i(uTex, 0)
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c.vars[i].uUVScale = gl.GetUniformLocation(ctx.Functions, prog, "uvScale")
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c.vars[i].uUVOffset = gl.GetUniformLocation(ctx.Functions, prog, "uvOffset")
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case materialColor:
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c.vars[i].uColor = gl.GetUniformLocation(ctx.Functions, prog, "color")
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}
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uCover := gl.GetUniformLocation(ctx.Functions, prog, "cover")
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ctx.Uniform1i(uCover, 1)
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c.vars[i].z = gl.GetUniformLocation(ctx.Functions, prog, "z")
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c.vars[i].uScale = gl.GetUniformLocation(ctx.Functions, prog, "scale")
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c.vars[i].uOffset = gl.GetUniformLocation(ctx.Functions, prog, "offset")
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c.vars[i].uCoverUVScale = gl.GetUniformLocation(ctx.Functions, prog, "uvCoverScale")
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c.vars[i].uCoverUVOffset = gl.GetUniformLocation(ctx.Functions, prog, "uvCoverOffset")
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}
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return c
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}
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func newStenciler(ctx *context) *stenciler {
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defFBO := gl.Framebuffer(ctx.GetBinding(gl.FRAMEBUFFER_BINDING))
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prog, err := gl.CreateProgram(ctx.Functions, stencilVSrc, stencilFSrc, pathAttribs)
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if err != nil {
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panic(err)
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}
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uAreaLUT := gl.GetUniformLocation(ctx.Functions, prog, "areaLUT")
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ctx.UseProgram(prog)
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ctx.Uniform1i(uAreaLUT, 0)
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areaLUT, err := loadLUT(ctx, genAreaLUT(256, 256))
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if err != nil {
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panic(err)
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}
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iprog, err := gl.CreateProgram(ctx.Functions, intersectVSrc, intersectFSrc, intersectAttribs)
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if err != nil {
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panic(err)
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}
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coverLoc := gl.GetUniformLocation(ctx.Functions, iprog, "cover")
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ctx.UseProgram(iprog)
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ctx.Uniform1i(coverLoc, 0)
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return &stenciler{
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ctx: ctx,
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defFBO: defFBO,
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prog: prog,
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iprog: iprog,
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areaLUT: areaLUT,
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uScale: gl.GetUniformLocation(ctx.Functions, prog, "scale"),
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uOffset: gl.GetUniformLocation(ctx.Functions, prog, "offset"),
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uPathOffset: gl.GetUniformLocation(ctx.Functions, prog, "pathOffset"),
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uIntersectUVScale: gl.GetUniformLocation(ctx.Functions, iprog, "uvScale"),
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uIntersectUVOffset: gl.GetUniformLocation(ctx.Functions, iprog, "uvOffset"),
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indexBuf: ctx.CreateBuffer(),
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}
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}
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func (s *fboSet) resize(ctx *context, sizes []image.Point) {
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// Add fbos.
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for i := len(s.fbos); i < len(sizes); i++ {
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tex := ctx.CreateTexture()
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ctx.BindTexture(gl.TEXTURE_2D, tex)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST)
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fbo := ctx.CreateFramebuffer()
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s.fbos = append(s.fbos, stencilFBO{
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fbo: fbo,
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tex: tex,
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})
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}
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// Resize fbos.
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for i, sz := range sizes {
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f := &s.fbos[i]
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// Resizing or recreating FBOs can introduce rendering stalls.
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// Avoid if the space waste is not too high.
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resize := sz.X > f.size.X || sz.Y > f.size.Y
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waste := float32(sz.X*sz.Y) / float32(f.size.X*f.size.Y)
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resize = resize || waste > 1.2
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if resize {
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f.size = sz
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ctx.BindTexture(gl.TEXTURE_2D, f.tex)
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tt := ctx.caps.floatTriple
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ctx.TexImage2D(gl.TEXTURE_2D, 0, tt.internalFormat, sz.X, sz.Y, tt.format, tt.typ, nil)
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ctx.BindFramebuffer(gl.FRAMEBUFFER, f.fbo)
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ctx.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, f.tex, 0)
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}
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}
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// Delete extra fbos.
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s.delete(ctx, len(sizes))
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}
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func (s *fboSet) invalidate(ctx *context) {
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for _, f := range s.fbos {
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ctx.BindFramebuffer(gl.FRAMEBUFFER, f.fbo)
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ctx.InvalidateFramebuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0)
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}
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}
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func (s *fboSet) delete(ctx *context, idx int) {
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for i := idx; i < len(s.fbos); i++ {
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f := s.fbos[i]
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ctx.DeleteFramebuffer(f.fbo)
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ctx.DeleteTexture(f.tex)
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}
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s.fbos = s.fbos[:idx]
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}
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func (s *stenciler) release() {
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s.fbos.delete(s.ctx, 0)
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s.ctx.DeleteTexture(s.areaLUT)
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s.ctx.DeleteProgram(s.prog)
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s.ctx.DeleteBuffer(s.indexBuf)
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}
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func (p *pather) release() {
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p.stenciler.release()
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p.coverer.release()
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}
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func (c *coverer) release() {
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for _, p := range c.prog {
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c.ctx.DeleteProgram(p)
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}
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}
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func buildPath(ctx *context, p *path.Path) *pathData {
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buf := ctx.CreateBuffer()
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ctx.BindBuffer(gl.ARRAY_BUFFER, buf)
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ctx.BufferData(gl.ARRAY_BUFFER, gl.BytesView(p.Vertices), gl.STATIC_DRAW)
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return &pathData{
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ncurves: len(p.Vertices),
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data: buf,
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}
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}
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func (p *pathData) release(ctx *context) {
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ctx.DeleteBuffer(p.data)
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}
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func (p *pather) begin(sizes []image.Point) {
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p.stenciler.begin(sizes)
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}
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func (p *pather) end() {
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p.stenciler.end()
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}
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func (p *pather) stencilPath(bounds image.Rectangle, offset f32.Point, uv image.Point, data *pathData) {
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p.stenciler.stencilPath(bounds, offset, uv, data)
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}
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func (s *stenciler) beginIntersect(sizes []image.Point) {
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s.ctx.ActiveTexture(gl.TEXTURE1)
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s.ctx.BindTexture(gl.TEXTURE_2D, gl.Texture{})
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s.ctx.ActiveTexture(gl.TEXTURE0)
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s.ctx.BlendFunc(gl.DST_COLOR, gl.ZERO)
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// 8 bit coverage is enough, but OpenGL ES only supports single channel
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// floating point formats. Replace with GL_RGB+GL_UNSIGNED_BYTE if
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// no floating point support is available.
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s.intersections.resize(s.ctx, sizes)
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s.ctx.ClearColor(1.0, 0.0, 0.0, 0.0)
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s.ctx.UseProgram(s.iprog)
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}
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func (s *stenciler) endIntersect() {
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s.ctx.BindFramebuffer(gl.FRAMEBUFFER, s.defFBO)
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}
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func (s *stenciler) invalidateFBO() {
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s.intersections.invalidate(s.ctx)
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s.fbos.invalidate(s.ctx)
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s.ctx.BindFramebuffer(gl.FRAMEBUFFER, s.defFBO)
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}
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func (s *stenciler) cover(idx int) stencilFBO {
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return s.fbos.fbos[idx]
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}
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func (s *stenciler) begin(sizes []image.Point) {
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s.ctx.ActiveTexture(gl.TEXTURE1)
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s.ctx.BindTexture(gl.TEXTURE_2D, gl.Texture{})
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s.ctx.ActiveTexture(gl.TEXTURE0)
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s.ctx.BlendFunc(gl.ONE, gl.ONE)
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s.fbos.resize(s.ctx, sizes)
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s.ctx.ClearColor(0.0, 0.0, 0.0, 0.0)
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s.ctx.BindTexture(gl.TEXTURE_2D, s.areaLUT)
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s.ctx.UseProgram(s.prog)
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s.ctx.EnableVertexAttribArray(attribPathCorner)
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s.ctx.EnableVertexAttribArray(attribPathMaxY)
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s.ctx.EnableVertexAttribArray(attribPathFrom)
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s.ctx.EnableVertexAttribArray(attribPathCtrl)
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s.ctx.EnableVertexAttribArray(attribPathTo)
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s.ctx.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, s.indexBuf)
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}
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func (s *stenciler) stencilPath(bounds image.Rectangle, offset f32.Point, uv image.Point, data *pathData) {
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s.ctx.BindBuffer(gl.ARRAY_BUFFER, data.data)
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s.ctx.Viewport(uv.X, uv.Y, bounds.Dx(), bounds.Dy())
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// Transform UI coordinates to OpenGL coordinates.
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texSize := f32.Point{X: float32(bounds.Dx()), Y: float32(bounds.Dy())}
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scale := f32.Point{X: 2 / texSize.X, Y: 2 / texSize.Y}
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orig := f32.Point{X: -1 - float32(bounds.Min.X)*2/texSize.X, Y: -1 - float32(bounds.Min.Y)*2/texSize.Y}
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s.ctx.Uniform2f(s.uScale, scale.X, scale.Y)
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s.ctx.Uniform2f(s.uOffset, orig.X, orig.Y)
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s.ctx.Uniform2f(s.uPathOffset, offset.X, offset.Y)
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// Draw in batches that fit in uint16 indices.
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start := 0
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nquads := data.ncurves / 4
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for start < nquads {
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batch := nquads - start
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if max := int(^uint16(0)) / 6; batch > max {
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batch = max
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}
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// Enlarge VBO if necessary.
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if batch > s.indexBufQuads {
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indices := make([]uint16, batch*6)
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for i := 0; i < batch; i++ {
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i := uint16(i)
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indices[i*6+0] = i*4 + 0
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indices[i*6+1] = i*4 + 1
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indices[i*6+2] = i*4 + 2
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indices[i*6+3] = i*4 + 2
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indices[i*6+4] = i*4 + 1
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indices[i*6+5] = i*4 + 3
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}
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s.ctx.BufferData(gl.ELEMENT_ARRAY_BUFFER, gl.BytesView(indices), gl.STATIC_DRAW)
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s.indexBufQuads = batch
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}
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off := path.VertStride * start * 4
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s.ctx.VertexAttribPointer(attribPathCorner, 2, gl.SHORT, false, path.VertStride, off+int(unsafe.Offsetof((*(*path.Vertex)(nil)).CornerX)))
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s.ctx.VertexAttribPointer(attribPathMaxY, 1, gl.FLOAT, false, path.VertStride, off+int(unsafe.Offsetof((*(*path.Vertex)(nil)).MaxY)))
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s.ctx.VertexAttribPointer(attribPathFrom, 2, gl.FLOAT, false, path.VertStride, off+int(unsafe.Offsetof((*(*path.Vertex)(nil)).FromX)))
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s.ctx.VertexAttribPointer(attribPathCtrl, 2, gl.FLOAT, false, path.VertStride, off+int(unsafe.Offsetof((*(*path.Vertex)(nil)).CtrlX)))
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s.ctx.VertexAttribPointer(attribPathTo, 2, gl.FLOAT, false, path.VertStride, off+int(unsafe.Offsetof((*(*path.Vertex)(nil)).ToX)))
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s.ctx.DrawElements(gl.TRIANGLES, batch*6, gl.UNSIGNED_SHORT, 0)
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start += batch
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}
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}
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func (s *stenciler) end() {
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s.ctx.DisableVertexAttribArray(attribPathCorner)
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s.ctx.DisableVertexAttribArray(attribPathMaxY)
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s.ctx.DisableVertexAttribArray(attribPathFrom)
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s.ctx.DisableVertexAttribArray(attribPathCtrl)
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s.ctx.DisableVertexAttribArray(attribPathTo)
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s.ctx.BindFramebuffer(gl.FRAMEBUFFER, s.defFBO)
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}
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func (p *pather) cover(z float32, mat materialType, col [4]float32, scale, off, uvScale, uvOff, coverScale, coverOff f32.Point) {
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p.coverer.cover(z, mat, col, scale, off, uvScale, uvOff, coverScale, coverOff)
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}
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func (c *coverer) cover(z float32, mat materialType, col [4]float32, scale, off, uvScale, uvOff, coverScale, coverOff f32.Point) {
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c.ctx.UseProgram(c.prog[mat])
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switch mat {
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case materialColor:
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c.ctx.Uniform4f(c.vars[mat].uColor, col[0], col[1], col[2], col[3])
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case materialTexture:
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c.ctx.Uniform2f(c.vars[mat].uUVScale, uvScale.X, uvScale.Y)
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c.ctx.Uniform2f(c.vars[mat].uUVOffset, uvOff.X, uvOff.Y)
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}
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c.ctx.Uniform1f(c.vars[mat].z, z)
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c.ctx.Uniform2f(c.vars[mat].uScale, scale.X, scale.Y)
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c.ctx.Uniform2f(c.vars[mat].uOffset, off.X, off.Y)
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c.ctx.Uniform2f(c.vars[mat].uCoverUVScale, coverScale.X, coverScale.Y)
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c.ctx.Uniform2f(c.vars[mat].uCoverUVOffset, coverOff.X, coverOff.Y)
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c.ctx.DrawArrays(gl.TRIANGLE_STRIP, 0, 4)
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}
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func loadLUT(ctx *context, lut *image.Gray) (gl.Texture, error) {
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tex := ctx.CreateTexture()
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ctx.BindTexture(gl.TEXTURE_2D, tex)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)
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ctx.TexParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
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ctx.PixelStorei(gl.UNPACK_ALIGNMENT, 1)
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if lut.Stride != lut.Bounds().Dx() {
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panic("unsupported LUT stride")
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}
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tt := ctx.caps.alphaTriple
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ctx.TexImage2D(gl.TEXTURE_2D, 0, tt.internalFormat, lut.Bounds().Dx(), lut.Bounds().Dy(), tt.format, tt.typ, lut.Pix)
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ctx.PixelStorei(gl.UNPACK_ALIGNMENT, 4)
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return tex, nil
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}
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const stencilVSrc = `
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#version 100
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precision highp float;
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uniform vec2 scale;
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uniform vec2 offset;
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uniform vec2 pathOffset;
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attribute vec2 corner;
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attribute float maxy;
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attribute vec2 from;
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attribute vec2 ctrl;
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attribute vec2 to;
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varying vec2 vFrom;
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varying vec2 vCtrl;
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varying vec2 vTo;
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void main() {
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// Add a one pixel overlap so curve quads cover their
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// entire curves. Could use conservative rasterization
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// if available.
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vec2 from = from + pathOffset;
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vec2 ctrl = ctrl + pathOffset;
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vec2 to = to + pathOffset;
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float maxy = maxy + pathOffset.y;
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vec2 pos;
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if (corner.x > 0.0) {
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// East.
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pos.x = max(max(from.x, ctrl.x), to.x)+1.0;
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} else {
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// West.
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pos.x = min(min(from.x, ctrl.x), to.x)-1.0;
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}
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if (corner.y > 0.0) {
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// North.
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pos.y = maxy + 1.0;
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} else {
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// South.
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pos.y = min(min(from.y, ctrl.y), to.y) - 1.0;
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}
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vFrom = from-pos;
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vCtrl = ctrl-pos;
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vTo = to-pos;
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pos *= scale;
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pos += offset;
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gl_Position = vec4(pos, 1, 1);
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}
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`
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const stencilFSrc = `
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#version 100
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precision mediump float;
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varying vec2 vFrom;
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varying vec2 vCtrl;
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varying vec2 vTo;
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uniform sampler2D areaLUT;
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void main() {
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float dx = vTo.x - vFrom.x;
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// Sort from and to in increasing order so the root below
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// is always the positive square root, if any.
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// We need the direction of the curve below, so this can't be
|
|
// done from the vertex shader.
|
|
bool increasing = vTo.x >= vFrom.x;
|
|
vec2 left = increasing ? vFrom : vTo;
|
|
vec2 right = increasing ? vTo : vFrom;
|
|
|
|
// The signed horizontal extent of the fragment.
|
|
vec2 extent = clamp(vec2(vFrom.x, vTo.x), -0.5, 0.5);
|
|
// Find the t where the curve crosses the middle of the
|
|
// extent, x₀.
|
|
// Given the bezier curve with x coordinates P₀, P₁, P₂
|
|
// where P₀ is at the origin, its x coordinate in t
|
|
// is given by:
|
|
//
|
|
// x(t) = 2(1-t)tP₁ + t²P₂
|
|
//
|
|
// Rearranging:
|
|
//
|
|
// x(t) = (P₂ - 2P₁)t² + 2P₁t
|
|
//
|
|
// Setting x(t) = x₀ and using Muller's quadratic formula ("Citardauq")
|
|
// for robustnesss,
|
|
//
|
|
// t = 2x₀/(2P₁±√(4P₁²+4(P₂-2P₁)x₀))
|
|
//
|
|
// which simplifies to
|
|
//
|
|
// t = x₀/(P₁±√(P₁²+(P₂-2P₁)x₀))
|
|
//
|
|
// Setting v = P₂-P₁,
|
|
//
|
|
// t = x₀/(P₁±√(P₁²+(v-P₁)x₀))
|
|
//
|
|
// t lie in [0; 1]; P₂ ≥ P₁ and P₁ ≥ 0 since we split curves where
|
|
// the control point lies before the start point or after the end point.
|
|
// It can then be shown that only the positive square root is valid.
|
|
float midx = mix(extent.x, extent.y, 0.5);
|
|
float x0 = midx - left.x;
|
|
vec2 p1 = vCtrl - left;
|
|
vec2 v = right - vCtrl;
|
|
float t = x0/(p1.x+sqrt(p1.x*p1.x+(v.x-p1.x)*x0));
|
|
// Find y(t) on the curve.
|
|
float y = mix(mix(left.y, vCtrl.y, t), mix(vCtrl.y, right.y, t), t);
|
|
// And the slope.
|
|
vec2 d_half = mix(p1, v, t);
|
|
float dy = d_half.y/d_half.x;
|
|
// Together, y and dy form a line approximation. The areaLUT table
|
|
// maps the line to a pixel coverage.
|
|
float width = extent.y - extent.x;
|
|
// The first axis maps y in [-8;+8] to [0;1].
|
|
float areau = y/16.0 + 0.5;
|
|
// The second axis maps slopes in [0;16] to [0;1]. The area is symmetric
|
|
// around dy = 0. Scale slope with extent width.
|
|
float areav = abs(dy*width)/16.0;
|
|
// Look up coverage from y and slope and scale to extent.
|
|
gl_FragColor.r = texture2D(areaLUT, vec2(areau, areav)).r*width;
|
|
}
|
|
`
|
|
|
|
const coverVSrc = `
|
|
#version 100
|
|
|
|
precision highp float;
|
|
|
|
uniform float z;
|
|
uniform vec2 scale;
|
|
uniform vec2 offset;
|
|
uniform vec2 uvScale;
|
|
uniform vec2 uvOffset;
|
|
uniform vec2 uvCoverScale;
|
|
uniform vec2 uvCoverOffset;
|
|
|
|
attribute vec2 pos;
|
|
|
|
varying vec2 vCoverUV;
|
|
|
|
attribute vec2 uv;
|
|
varying vec2 vUV;
|
|
|
|
void main() {
|
|
gl_Position = vec4(pos*scale + offset, z, 1);
|
|
vUV = uv*uvScale + uvOffset;
|
|
vCoverUV = uv*uvCoverScale+uvCoverOffset;
|
|
}
|
|
`
|
|
|
|
const coverFSrc = `
|
|
#version 100
|
|
|
|
precision mediump float;
|
|
|
|
// Use high precision to be pixel accurate for
|
|
// large cover atlases.
|
|
varying highp vec2 vCoverUV;
|
|
uniform sampler2D cover;
|
|
varying vec2 vUV;
|
|
|
|
HEADER
|
|
|
|
void main() {
|
|
gl_FragColor = GET_COLOR;
|
|
float cover = abs(texture2D(cover, vCoverUV).r);
|
|
gl_FragColor *= cover;
|
|
}
|
|
`
|
|
|
|
const intersectVSrc = `
|
|
#version 100
|
|
|
|
precision highp float;
|
|
|
|
attribute vec2 pos;
|
|
attribute vec2 uv;
|
|
|
|
uniform vec2 uvScale;
|
|
uniform vec2 uvOffset;
|
|
|
|
varying vec2 vUV;
|
|
|
|
void main() {
|
|
vec2 p = pos;
|
|
p.y = -p.y;
|
|
gl_Position = vec4(p, 0, 1);
|
|
vUV = uv*uvScale + uvOffset;
|
|
}
|
|
`
|
|
|
|
const intersectFSrc = `
|
|
#version 100
|
|
|
|
precision mediump float;
|
|
|
|
// Use high precision to be pixel accurate for
|
|
// large cover atlases.
|
|
varying highp vec2 vUV;
|
|
uniform sampler2D cover;
|
|
|
|
void main() {
|
|
float cover = abs(texture2D(cover, vUV).r);
|
|
gl_FragColor.r = cover;
|
|
}
|
|
`
|