[graphite] Add shell for TessellateStrokeRenderStep

Bug: skia:12703
Change-Id: I9cc44db555a7bb03e4afeaedac4052c796349c5e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/540621
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

gn/graphite.gni

@@ -122,6 +122,8 @@ skia_graphite_sources = [
   "$_src/render/StencilAndFillPathRenderer.cpp",
   "$_src/render/TessellateCurvesRenderStep.cpp",
   "$_src/render/TessellateCurvesRenderStep.h",
+  "$_src/render/TessellateStrokesRenderStep.cpp",
+  "$_src/render/TessellateStrokesRenderStep.h",
   "$_src/render/TessellateWedgesRenderStep.cpp",
   "$_src/render/TessellateWedgesRenderStep.h",
 ]

src/gpu/graphite/render/BUILD.bazel

@@ -122,3 +122,22 @@ generated_cc_atom(
         "//src/gpu/tessellate:LinearTolerances_hdr",
     ],
 )
+
+generated_cc_atom(
+    name = "TessellateStrokesRenderStep_hdr",
+    hdrs = ["TessellateStrokesRenderStep.h"],
+    visibility = ["//:__subpackages__"],
+    deps = ["//src/gpu/graphite:Renderer_hdr"],
+)
+
+generated_cc_atom(
+    name = "TessellateStrokesRenderStep_src",
+    srcs = ["TessellateStrokesRenderStep.cpp"],
+    visibility = ["//:__subpackages__"],
+    deps = [
+        ":TessellateStrokesRenderStep_hdr",
+        "//src/gpu/graphite:DrawGeometry_hdr",
+        "//src/gpu/graphite:DrawTypes_hdr",
+        "//src/gpu/graphite:DrawWriter_hdr",
+    ],
+)

src/gpu/graphite/render/TessellateStrokesRenderStep.cpp

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "src/gpu/graphite/render/TessellateStrokesRenderStep.h"
+
+#include "src/gpu/graphite/DrawGeometry.h"
+#include "src/gpu/graphite/DrawTypes.h"
+#include "src/gpu/graphite/DrawWriter.h"
+
+
+namespace skgpu::graphite {
+
+namespace {
+
+// TODO: De-duplicate with the same settings that's currently used for convex path rendering
+// in StencilAndFillPathRenderer.cpp
+static constexpr DepthStencilSettings kDirectShadingPass = {
+        /*frontStencil=*/{},
+        /*backStencil=*/ {},
+        /*refValue=*/    0,
+        /*stencilTest=*/ false,
+        /*depthCompare=*/CompareOp::kGreater,
+        /*depthTest=*/   true,
+        /*depthWrite=*/  true
+};
+
+}  // namespace
+
+// TODO: specify attributes and uniforms
+TessellateStrokesRenderStep::TessellateStrokesRenderStep()
+        : RenderStep("TessellateStrokeRenderStep",
+                     "",
+                     Flags::kRequiresMSAA,
+                     /*uniforms=*/{},
+                     PrimitiveType::kTriangleStrip,
+                     kDirectShadingPass,
+                     /*vertexAttrs=*/  {},
+                     /*instanceAttrs=*/{}) {}
+
+TessellateStrokesRenderStep::~TessellateStrokesRenderStep() {}
+
+const char* TessellateStrokesRenderStep::vertexSkSL() const {
+    SkASSERT(false);
+    return ""; // TODO: implement this
+}
+
+void TessellateStrokesRenderStep::writeVertices(DrawWriter* dw, const DrawGeometry& geom) const {
+    // TODO: implement this
+
+}
+
+void TessellateStrokesRenderStep::writeUniforms(const DrawGeometry&,
+                                                SkPipelineDataGatherer*) const {
+    // TODO: implement this
+}
+
+}  // namespace skgpu::graphite

src/gpu/graphite/render/TessellateStrokesRenderStep.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef skgpu_graphite_render_TessellateStrokesRenderStep_DEFINED
+#define skgpu_graphite_render_TessellateStrokesRenderStep_DEFINED
+
+#include "src/gpu/graphite/Renderer.h"
+
+namespace skgpu::graphite {
+
+class TessellateStrokesRenderStep final : public RenderStep {
+public:
+    // TODO: If this takes DepthStencilSettings directly and a way to adjust the flags to specify
+    // that it performs shading, this RenderStep definition could be used to handle inverse-filled
+    // stroke draws.
+    TessellateStrokesRenderStep();
+
+    ~TessellateStrokesRenderStep() override;
+
+    const char* vertexSkSL() const override;
+    void writeVertices(DrawWriter*, const DrawGeometry&) const override;
+    void writeUniforms(const DrawGeometry&, SkPipelineDataGatherer*) const override;
+};
+
+}  // namespace skgpu::graphite
+
+#endif // skgpu_graphite_render_TessellateStrokesRenderStep_DEFINED