1 /* 2 * Copyright 2020 Google LLC. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 #ifndef GrStrokeTessellationShader_DEFINED 8 #define GrStrokeTessellationShader_DEFINED 9 10 #include "include/core/SkStrokeRec.h" 11 #include "include/private/SkColorData.h" 12 #include "include/private/base/SkTArray.h" 13 #include "src/gpu/ganesh/tessellate/GrTessellationShader.h" 14 #include "src/gpu/tessellate/Tessellation.h" 15 16 #include <memory> 17 18 class SkMatrix; 19 struct GrShaderCaps; 20 21 namespace skgpu { 22 class KeyBuilder; 23 } 24 25 // Tessellates a batch of stroke patches directly to the canvas. Tessellated stroking works by 26 // creating stroke-width, orthogonal edges at set locations along the curve and then connecting them 27 // with a quad strip. These orthogonal edges come from two different sets: "parametric edges" and 28 // "radial edges". Parametric edges are spaced evenly in the parametric sense, and radial edges 29 // divide the curve's _rotation_ into even steps. The tessellation shader evaluates both sets of 30 // edges and sorts them into a single quad strip. With this combined set of edges we can stroke any 31 // curve, regardless of curvature. 32 class GrStrokeTessellationShader : public GrTessellationShader { 33 using PatchAttribs = skgpu::tess::PatchAttribs; 34 35 public: 36 37 // 'viewMatrix' is applied to the geometry post tessellation. It cannot have perspective. 38 GrStrokeTessellationShader(const GrShaderCaps&, PatchAttribs, const SkMatrix& viewMatrix, 39 const SkStrokeRec&, SkPMColor4f); 40 attribs()41 PatchAttribs attribs() const { return fPatchAttribs; } hasDynamicStroke()42 bool hasDynamicStroke() const { return fPatchAttribs & PatchAttribs::kStrokeParams; } hasDynamicColor()43 bool hasDynamicColor() const { return fPatchAttribs & PatchAttribs::kColor; } hasExplicitCurveType()44 bool hasExplicitCurveType() const { return fPatchAttribs & PatchAttribs::kExplicitCurveType; } stroke()45 const SkStrokeRec& stroke() const { return fStroke;} 46 47 private: name()48 const char* name() const override { return "GrStrokeTessellationShader"; } 49 void addToKey(const GrShaderCaps&, skgpu::KeyBuilder*) const override; 50 std::unique_ptr<ProgramImpl> makeProgramImpl(const GrShaderCaps&) const final; 51 52 const PatchAttribs fPatchAttribs; 53 const SkStrokeRec fStroke; 54 55 constexpr static int kMaxAttribCount = 6; 56 skia_private::STArray<kMaxAttribCount, Attribute> fAttribs; 57 58 class Impl; 59 }; 60 61 #endif 62