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path.go
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path.go
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// SPDX-License-Identifier: Unlicense OR MIT
package gpu
// GPU accelerated path drawing using the algorithms from
// Pathfinder (https://github.com/servo/pathfinder).
import (
"encoding/binary"
"image"
"math"
"unsafe"
"github.com/cybriq/p9/pkg/gel/gio/f32"
"github.com/cybriq/p9/pkg/gel/gio/gpu/internal/driver"
"github.com/cybriq/p9/pkg/gel/gio/internal/byteslice"
"github.com/cybriq/p9/pkg/gel/gio/internal/f32color"
)
type pather struct {
ctx driver.Device
viewport image.Point
stenciler *stenciler
coverer *coverer
}
type coverer struct {
ctx driver.Device
prog [3]*program
texUniforms *coverTexUniforms
colUniforms *coverColUniforms
linearGradientUniforms *coverLinearGradientUniforms
layout driver.InputLayout
}
type coverTexUniforms struct {
vert struct {
coverUniforms
_ [12]byte // Padding to multiple of 16.
}
}
type coverColUniforms struct {
vert struct {
coverUniforms
_ [12]byte // Padding to multiple of 16.
}
frag struct {
colorUniforms
}
}
type coverLinearGradientUniforms struct {
vert struct {
coverUniforms
_ [12]byte // Padding to multiple of 16.
}
frag struct {
gradientUniforms
}
}
type coverUniforms struct {
transform [4]float32
uvCoverTransform [4]float32
uvTransformR1 [4]float32
uvTransformR2 [4]float32
z float32
}
type stenciler struct {
ctx driver.Device
prog struct {
prog *program
uniforms *stencilUniforms
layout driver.InputLayout
}
iprog struct {
prog *program
uniforms *intersectUniforms
layout driver.InputLayout
}
fbos fboSet
intersections fboSet
indexBuf driver.Buffer
}
type stencilUniforms struct {
vert struct {
transform [4]float32
pathOffset [2]float32
_ [8]byte // Padding to multiple of 16.
}
}
type intersectUniforms struct {
vert struct {
uvTransform [4]float32
subUVTransform [4]float32
}
}
type fboSet struct {
fbos []stencilFBO
}
type stencilFBO struct {
size image.Point
fbo driver.Framebuffer
tex driver.Texture
}
type pathData struct {
ncurves int
data driver.Buffer
}
// vertex data suitable for passing to vertex programs.
type vertex struct {
// Corner encodes the corner: +0.5 for south, +.25 for east.
Corner float32
MaxY float32
FromX, FromY float32
CtrlX, CtrlY float32
ToX, ToY float32
}
func (v vertex) encode(d []byte, maxy uint32) {
bo := binary.LittleEndian
bo.PutUint32(d[0:], math.Float32bits(v.Corner))
bo.PutUint32(d[4:], maxy)
bo.PutUint32(d[8:], math.Float32bits(v.FromX))
bo.PutUint32(d[12:], math.Float32bits(v.FromY))
bo.PutUint32(d[16:], math.Float32bits(v.CtrlX))
bo.PutUint32(d[20:], math.Float32bits(v.CtrlY))
bo.PutUint32(d[24:], math.Float32bits(v.ToX))
bo.PutUint32(d[28:], math.Float32bits(v.ToY))
}
const (
// Number of path quads per draw batch.
pathBatchSize = 10000
// Size of a vertex as sent to gpu
vertStride = 8 * 4
)
func newPather(ctx driver.Device) *pather {
return &pather{
ctx: ctx,
stenciler: newStenciler(ctx),
coverer: newCoverer(ctx),
}
}
func newCoverer(ctx driver.Device) *coverer {
c := &coverer{
ctx: ctx,
}
c.colUniforms = new(coverColUniforms)
c.texUniforms = new(coverTexUniforms)
c.linearGradientUniforms = new(coverLinearGradientUniforms)
prog, layout, err := createColorPrograms(
ctx, shader_cover_vert,
shader_cover_frag,
[3]interface{}{
&c.colUniforms.vert, &c.linearGradientUniforms.vert,
&c.texUniforms.vert,
},
[3]interface{}{
&c.colUniforms.frag,
&c.linearGradientUniforms.frag,
nil,
},
)
if err != nil {
panic(err)
}
c.prog = prog
c.layout = layout
return c
}
func newStenciler(ctx driver.Device) *stenciler {
// Allocate a suitably large index buffer for drawing paths.
indices := make([]uint16, pathBatchSize*6)
for i := 0; i < pathBatchSize; i++ {
i := uint16(i)
indices[i*6+0] = i*4 + 0
indices[i*6+1] = i*4 + 1
indices[i*6+2] = i*4 + 2
indices[i*6+3] = i*4 + 2
indices[i*6+4] = i*4 + 1
indices[i*6+5] = i*4 + 3
}
indexBuf, err := ctx.NewImmutableBuffer(
driver.BufferBindingIndices,
byteslice.Slice(indices),
)
if err != nil {
panic(err)
}
progLayout, err := ctx.NewInputLayout(
shader_stencil_vert,
[]driver.InputDesc{
{
Type: driver.DataTypeFloat, Size: 1,
Offset: int(unsafe.Offsetof((*(*vertex)(nil)).Corner)),
},
{
Type: driver.DataTypeFloat, Size: 1,
Offset: int(unsafe.Offsetof((*(*vertex)(nil)).MaxY)),
},
{
Type: driver.DataTypeFloat, Size: 2,
Offset: int(unsafe.Offsetof((*(*vertex)(nil)).FromX)),
},
{
Type: driver.DataTypeFloat, Size: 2,
Offset: int(unsafe.Offsetof((*(*vertex)(nil)).CtrlX)),
},
{
Type: driver.DataTypeFloat, Size: 2,
Offset: int(unsafe.Offsetof((*(*vertex)(nil)).ToX)),
},
},
)
if err != nil {
panic(err)
}
iprogLayout, err := ctx.NewInputLayout(
shader_intersect_vert,
[]driver.InputDesc{
{Type: driver.DataTypeFloat, Size: 2, Offset: 0},
{Type: driver.DataTypeFloat, Size: 2, Offset: 4 * 2},
},
)
if err != nil {
panic(err)
}
st := &stenciler{
ctx: ctx,
indexBuf: indexBuf,
}
prog, err := ctx.NewProgram(shader_stencil_vert, shader_stencil_frag)
if err != nil {
panic(err)
}
st.prog.uniforms = new(stencilUniforms)
vertUniforms := newUniformBuffer(ctx, &st.prog.uniforms.vert)
st.prog.prog = newProgram(prog, vertUniforms, nil)
st.prog.layout = progLayout
iprog, err := ctx.NewProgram(shader_intersect_vert, shader_intersect_frag)
if err != nil {
panic(err)
}
st.iprog.uniforms = new(intersectUniforms)
vertUniforms = newUniformBuffer(ctx, &st.iprog.uniforms.vert)
st.iprog.prog = newProgram(iprog, vertUniforms, nil)
st.iprog.layout = iprogLayout
return st
}
func (s *fboSet) resize(ctx driver.Device, sizes []image.Point) {
// Add fbos.
for i := len(s.fbos); i < len(sizes); i++ {
s.fbos = append(s.fbos, stencilFBO{})
}
// Resize fbos.
for i, sz := range sizes {
f := &s.fbos[i]
// Resizing or recreating FBOs can introduce rendering stalls.
// Avoid if the space waste is not too high.
resize := sz.X > f.size.X || sz.Y > f.size.Y
waste := float32(sz.X*sz.Y) / float32(f.size.X*f.size.Y)
resize = resize || waste > 1.2
if resize {
if f.fbo != nil {
f.fbo.Release()
f.tex.Release()
}
tex, err := ctx.NewTexture(
driver.TextureFormatFloat, sz.X, sz.Y,
driver.FilterNearest, driver.FilterNearest,
driver.BufferBindingTexture|driver.BufferBindingFramebuffer,
)
if err != nil {
panic(err)
}
fbo, err := ctx.NewFramebuffer(tex, 0)
if err != nil {
panic(err)
}
f.size = sz
f.tex = tex
f.fbo = fbo
}
}
// Delete extra fbos.
s.delete(ctx, len(sizes))
}
func (s *fboSet) invalidate(ctx driver.Device) {
for _, f := range s.fbos {
f.fbo.Invalidate()
}
}
func (s *fboSet) delete(ctx driver.Device, idx int) {
for i := idx; i < len(s.fbos); i++ {
f := s.fbos[i]
f.fbo.Release()
f.tex.Release()
}
s.fbos = s.fbos[:idx]
}
func (s *stenciler) release() {
s.fbos.delete(s.ctx, 0)
s.prog.layout.Release()
s.prog.prog.Release()
s.iprog.layout.Release()
s.iprog.prog.Release()
s.indexBuf.Release()
}
func (p *pather) release() {
p.stenciler.release()
p.coverer.release()
}
func (c *coverer) release() {
for _, p := range c.prog {
p.Release()
}
c.layout.Release()
}
func buildPath(ctx driver.Device, p []byte) pathData {
buf, err := ctx.NewImmutableBuffer(driver.BufferBindingVertices, p)
if err != nil {
panic(err)
}
return pathData{
ncurves: len(p) / vertStride,
data: buf,
}
}
func (p pathData) release() {
p.data.Release()
}
func (p *pather) begin(sizes []image.Point) {
p.stenciler.begin(sizes)
}
func (p *pather) stencilPath(
bounds image.Rectangle, offset f32.Point,
uv image.Point, data pathData,
) {
p.stenciler.stencilPath(bounds, offset, uv, data)
}
func (s *stenciler) beginIntersect(sizes []image.Point) {
s.ctx.BlendFunc(driver.BlendFactorDstColor, driver.BlendFactorZero)
// 8 bit coverage is enough, but OpenGL ES only supports single channel
// floating point formats. Replace with GL_RGB+GL_UNSIGNED_BYTE if
// no floating point support is available.
s.intersections.resize(s.ctx, sizes)
s.ctx.BindProgram(s.iprog.prog.prog)
}
func (s *stenciler) invalidateFBO() {
s.intersections.invalidate(s.ctx)
s.fbos.invalidate(s.ctx)
}
func (s *stenciler) cover(idx int) stencilFBO {
return s.fbos.fbos[idx]
}
func (s *stenciler) begin(sizes []image.Point) {
s.ctx.BlendFunc(driver.BlendFactorOne, driver.BlendFactorOne)
s.fbos.resize(s.ctx, sizes)
s.ctx.BindProgram(s.prog.prog.prog)
s.ctx.BindInputLayout(s.prog.layout)
s.ctx.BindIndexBuffer(s.indexBuf)
}
func (s *stenciler) stencilPath(
bounds image.Rectangle, offset f32.Point,
uv image.Point, data pathData,
) {
s.ctx.Viewport(uv.X, uv.Y, bounds.Dx(), bounds.Dy())
// Transform UI coordinates to OpenGL coordinates.
texSize := f32.Point{X: float32(bounds.Dx()), Y: float32(bounds.Dy())}
scale := f32.Point{X: 2 / texSize.X, Y: 2 / texSize.Y}
orig := f32.Point{
X: -1 - float32(bounds.Min.X)*2/texSize.X,
Y: -1 - float32(bounds.Min.Y)*2/texSize.Y,
}
s.prog.uniforms.vert.transform = [4]float32{
scale.X, scale.Y, orig.X,
orig.Y,
}
s.prog.uniforms.vert.pathOffset = [2]float32{offset.X, offset.Y}
s.prog.prog.UploadUniforms()
// Draw in batches that fit in uint16 indices.
start := 0
nquads := data.ncurves / 4
for start < nquads {
batch := nquads - start
if max := pathBatchSize; batch > max {
batch = max
}
off := vertStride * start * 4
s.ctx.BindVertexBuffer(data.data, vertStride, off)
s.ctx.DrawElements(driver.DrawModeTriangles, 0, batch*6)
start += batch
}
}
func (p *pather) cover(
z float32, mat materialType, col f32color.RGBA,
col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D,
coverScale, coverOff f32.Point,
) {
p.coverer.cover(
z, mat, col, col1, col2, scale, off, uvTrans, coverScale,
coverOff,
)
}
func (c *coverer) cover(
z float32, mat materialType, col f32color.RGBA,
col1, col2 f32color.RGBA, scale, off f32.Point, uvTrans f32.Affine2D,
coverScale, coverOff f32.Point,
) {
p := c.prog[mat]
c.ctx.BindProgram(p.prog)
var uniforms *coverUniforms
switch mat {
case materialColor:
c.colUniforms.frag.color = col
uniforms = &c.colUniforms.vert.coverUniforms
case materialLinearGradient:
c.linearGradientUniforms.frag.color1 = col1
c.linearGradientUniforms.frag.color2 = col2
t1, t2, t3, t4, t5, t6 := uvTrans.Elems()
c.linearGradientUniforms.vert.uvTransformR1 = [4]float32{t1, t2, t3, 0}
c.linearGradientUniforms.vert.uvTransformR2 = [4]float32{t4, t5, t6, 0}
uniforms = &c.linearGradientUniforms.vert.coverUniforms
case materialTexture:
t1, t2, t3, t4, t5, t6 := uvTrans.Elems()
c.texUniforms.vert.uvTransformR1 = [4]float32{t1, t2, t3, 0}
c.texUniforms.vert.uvTransformR2 = [4]float32{t4, t5, t6, 0}
uniforms = &c.texUniforms.vert.coverUniforms
}
uniforms.z = z
uniforms.transform = [4]float32{scale.X, scale.Y, off.X, off.Y}
uniforms.uvCoverTransform = [4]float32{
coverScale.X, coverScale.Y,
coverOff.X, coverOff.Y,
}
p.UploadUniforms()
c.ctx.DrawArrays(driver.DrawModeTriangleStrip, 0, 4)
}
func init() {
// Check that struct vertex has the expected size and
// that it contains no padding.
if unsafe.Sizeof(*(*vertex)(nil)) != vertStride {
panic("unexpected struct size")
}
}