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Copy pathscene.go
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214 lines (193 loc) · 6.17 KB
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// Copyright 2022 the Vello Authors
// Copyright 2024 Dominik Honnef and contributors
// SPDX-License-Identifier: Apache-2.0 OR MIT
package jello
import (
"fmt"
"slices"
"honnef.co/go/curve"
"honnef.co/go/jello/encoding"
"honnef.co/go/jello/gfx"
"honnef.co/go/jello/jmath"
"honnef.co/go/jello/renderer"
)
const debugTrace = false
type Scene struct {
encoding encoding.Encoding
estimator renderer.BumpEstimator
}
func (s *Scene) Reset() {
s.encoding.Reset()
s.estimator.Reset()
}
// Encoding returns the scene encoding. The scene mustn't be manipulated
// concurrently with using the encoding.
func (s *Scene) Encoding() *encoding.Encoding {
return &s.encoding
}
func (s *Scene) bumpEstimate(affine *curve.Affine) renderer.BumpAllocatorMemory {
var trans *jmath.Transform
if affine != nil {
ret := jmath.TransformFromKurbo(*affine)
trans = &ret
}
return s.estimator.Tally(trans)
}
func (s *Scene) PushLayer(
blend gfx.BlendMode,
alpha float32,
clipTransform curve.Affine,
clip curve.BezPath,
) {
if debugTrace {
fmt.Println("{")
fmt.Println("\tvar clip curve.BezPath")
for _, el := range clip {
fmt.Printf("\tclip.Push(%#v)\n", el)
}
fmt.Printf("\ts.PushLayer(%#v, %g, %#v, clip)\n", blend, alpha, clipTransform)
fmt.Println("}")
}
t := jmath.TransformFromKurbo(clipTransform)
s.encoding.EncodeTransform(t)
s.encoding.EncodeFillStyle(gfx.NonZero)
if !s.encoding.EncodePath(clip, true) {
// If the layer shape is invalid, encode a valid empty path. This suppresses
// all drawing until the layer is popped.
s.encoding.EncodePath(slices.Collect(curve.Rect{}.PathElements(0.1)), true)
s.encoding.EncodeEmptyShape()
path := curve.BezPath{
curve.MoveTo(curve.Pt(0, 0)),
curve.LineTo(curve.Pt(0, 0)),
}
s.estimator.CountPath(path, t, nil)
} else {
s.estimator.CountPath(clip, t, nil)
}
s.encoding.EncodeBeginClip(blend, min(max(alpha, 0), 1))
}
func (s *Scene) PopLayer() {
if debugTrace {
fmt.Println("s.PopLayer()")
}
s.encoding.EncodeEndClip()
}
func (s *Scene) Fill(
style gfx.Fill,
transform curve.Affine,
brush gfx.Brush,
brushTransform curve.Affine,
path curve.BezPath,
) {
if debugTrace {
fmt.Println("{")
fmt.Println("\tvar clip curve.BezPath")
for _, el := range path {
fmt.Printf("\tclip.Push(%#v)\n", el)
}
fmt.Printf("\ts.Fill(%d, %#v, %#v, %#v, clip)\n", style, transform, brush, brushTransform)
fmt.Println("}")
}
t := jmath.TransformFromKurbo(transform)
s.encoding.EncodeTransform(t)
s.encoding.EncodeFillStyle(style)
if s.encoding.EncodePath(path, true) {
if brushTransform != curve.Identity {
if s.encoding.EncodeTransform(jmath.TransformFromKurbo(transform.Mul(brushTransform))) {
s.encoding.SwapLastPathTags()
}
}
s.encoding.EncodeBrush(brush, 1.0)
s.estimator.CountPath(path, t, nil)
}
}
func (s *Scene) Stroke(
style curve.Stroke,
transform curve.Affine,
b gfx.Brush,
brushTransform curve.Affine,
shape curve.BezPath,
) {
// The setting for tolerance are a compromise. For most applications,
// shape tolerance doesn't matter, as the input is likely Bézier paths,
// which is exact. Note that shape tolerance is hard-coded as 0.1 in
// the encoding crate.
//
// Stroke tolerance is a different matter. Generally, the cost scales
// with inverse O(n^6), so there is moderate rendering cost to setting
// too fine a value. On the other hand, error scales with the transform
// applied post-stroking, so may exceed visible threshold. When we do
// GPU-side stroking, the transform will be known. In the meantime,
// this is a compromise.
const shapeTolerance = 0.01
const strokeTolerance = shapeTolerance
if debugTrace {
fmt.Println("{")
fmt.Println("\tvar clip curve.BezPath")
for _, el := range shape {
fmt.Printf("\tclip.Push(%#v)\n", el)
}
fmt.Printf("\ts.Stroke(%#v, %#v, %#v, %#v, clip)\n", style, transform, b, brushTransform)
fmt.Println("}")
}
const gpuStrokes = true // Set this to `true` to enable GPU-side stroking
if gpuStrokes {
t := jmath.TransformFromKurbo(transform)
s.encoding.EncodeTransform(t)
s.encoding.EncodeStrokeStyle(style)
// We currently don't support dashing on the GPU. If the style has a dash pattern, then
// we convert it into stroked paths on the CPU and encode those as individual draw
// objects.
var encodeResult bool
if len(style.DashPattern) == 0 {
s.estimator.CountPath(shape, t, &style)
encodeResult = s.encoding.EncodePath(shape, false)
} else {
// TODO: We currently collect the output of the dash iterator because
// `encode_path_elements` wants to consume the iterator. We want to avoid calling
// `dash` twice when `bump_estimate` is enabled because it internally allocates.
// Bump estimation will move to resolve time rather than scene construction time,
// so we can revert this back to not collecting when that happens.
dashed := slices.Collect(curve.Dash(
slices.Values(shape),
style.DashOffset,
style.DashPattern,
))
// We turn the iterator into a slice
5589
and then turn it into an
// iterator again to avoid doing the curve.Dash work twice.
s.estimator.CountPath(dashed, t, &style)
encodeResult = s.encoding.EncodePath(dashed, false)
}
if encodeResult {
if brushTransform != curve.Identity {
if s.encoding.EncodeTransform(jmath.TransformFromKurbo(transform.Mul(brushTransform))) {
s.encoding.SwapLastPathTags()
}
}
s.encoding.EncodeBrush(b, 1.0)
}
} else {
stroked := curve.StrokePath(
slices.Values(shape),
style,
curve.StrokeOpts{},
strokeTolerance,
)
s.Fill(gfx.NonZero, transform, b, brushTransform, slices.Collect(stroked))
}
}
func (s *Scene) Append(other *Scene, transform curve.Affine) {
// OPT(dh): we'd like to combine multiple scenes without having to copy data around
t := jmath.TransformFromKurbo(transform)
s.encoding.Append(&other.encoding, t)
s.estimator.Append(&other.estimator, &t)
}
// ApplyTransform applies an affine transformation to everything that has
// already been drawn in the scene. It does not affect future drawing
// operations.
//
// This can be used, for example, to apply HiDPI scaling.
func (s *Scene) ApplyTransform(transform curve.Affine) {
t := jmath.TransformFromKurbo(transform)
s.encoding.ApplyTransform(t)
}