From aac53ad0b548b818490c67b1dc964c01a8f0a392 Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Wed, 20 Oct 2021 09:59:07 +0200
Subject: [PATCH] gpu: don't alias stroked paths with outline paths

The default renderer caches pre-processed paths for efficient re-use,
but failed to distinguish outline paths from stroke paths.

Fixes gio#294

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 gpu/gpu.go                                    |  15 ++++++------
 gpu/internal/rendertest/clip_test.go          |  22 ++++++++++++++++++
 .../rendertest/refs/TestPathReuse.png         | Bin 0 -> 1278 bytes
 3 files changed, 30 insertions(+), 7 deletions(-)
 create mode 100644 gpu/internal/rendertest/refs/TestPathReuse.png

diff --git a/gpu/gpu.go b/gpu/gpu.go
index 0ca6b689..a01eb1ff 100644
--- a/gpu/gpu.go
+++ b/gpu/gpu.go
@@ -149,6 +149,8 @@ type quadsOp struct {
 }
 
 type opKey struct {
+	outline        bool
+	strokeWidth    float32
 	sx, hx, sy, hy float32
 	ops.Key
 }
@@ -904,9 +906,8 @@ func (k opKey) SetTransform(t f32.Affine2D) opKey {
 
 func (d *drawOps) collectOps(r *ops.Reader, viewport f32.Rectangle) {
 	var (
-		quads    quadsOp
-		strWidth float32
-		state    drawState
+		quads quadsOp
+		state drawState
 	)
 	reset := func() {
 		state = drawState{
@@ -931,7 +932,7 @@ loop:
 			d.transStack = d.transStack[:n-1]
 
 		case ops.TypeStroke:
-			strWidth = decodeStrokeOp(encOp.Data)
+			quads.key.strokeWidth = decodeStrokeOp(encOp.Data)
 
 		case ops.TypePath:
 			encOp, ok = r.Decode()
@@ -939,11 +940,12 @@ loop:
 				break loop
 			}
 			quads.aux = encOp.Data[ops.TypeAuxLen:]
-			quads.key = opKey{Key: encOp.Key}
+			quads.key.Key = encOp.Key
 
 		case ops.TypeClip:
 			var op clipOp
 			op.decode(encOp.Data)
+			quads.key.outline = op.outline
 			bounds := op.bounds
 			trans, off := splitTransform(state.t)
 			if len(quads.aux) > 0 {
@@ -957,7 +959,7 @@ loop:
 					op.bounds = v.bounds
 				} else {
 					pathData, bounds := d.buildVerts(
-						quads.aux, trans, op.outline, strWidth,
+						quads.aux, trans, quads.key.outline, quads.key.strokeWidth,
 					)
 					op.bounds = bounds
 					quads.aux = pathData
@@ -971,7 +973,6 @@ loop:
 			}
 			d.addClipPath(&state, quads.aux, quads.key, op.bounds, off, op.push)
 			quads = quadsOp{}
-			strWidth = 0
 		case ops.TypePopClip:
 			for {
 				push := state.cpath.push
diff --git a/gpu/internal/rendertest/clip_test.go b/gpu/internal/rendertest/clip_test.go
index dbee98fc..22703617 100644
--- a/gpu/internal/rendertest/clip_test.go
+++ b/gpu/internal/rendertest/clip_test.go
@@ -4,6 +4,7 @@ package rendertest
 
 import (
 	"image"
+	"image/color"
 	"math"
 	"testing"
 
@@ -183,3 +184,24 @@ func TestStrokedPathZeroWidth(t *testing.T) {
 		r.expect(65, 50, transparent)
 	})
 }
+
+func TestPathReuse(t *testing.T) {
+	run(t, func(o *op.Ops) {
+		var path clip.Path
+		path.Begin(o)
+		path.MoveTo(f32.Pt(60, 10))
+		path.LineTo(f32.Pt(110, 75))
+		path.LineTo(f32.Pt(10, 75))
+		path.Close()
+		spec := path.End()
+
+		outline := clip.Outline{Path: spec}.Op().Push(o)
+		paint.Fill(o, color.NRGBA{R: 0xFF, A: 0xFF})
+		outline.Pop()
+
+		stroke := clip.Stroke{Path: spec, Width: 3}.Op().Push(o)
+		paint.Fill(o, color.NRGBA{B: 0xFF, A: 0xFF})
+		stroke.Pop()
+	}, func(r result) {
+	})
+}
diff --git a/gpu/internal/rendertest/refs/TestPathReuse.png b/gpu/internal/rendertest/refs/TestPathReuse.png
new file mode 100644
index 0000000000000000000000000000000000000000..7a178e546633c6c327a1840e19faeb96c2e368e6
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