Fix for degenerate stroke rect

src/gpu/batches/GrAAStrokeRectBatch.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrAAStrokeRectBatch.h"
 
 #include "GrBatchFlushState.h"
@@ skipping 36 matching lines @@
 public:
     DEFINE_BATCH_CLASS_ID
 
     // TODO support AA rotated stroke rects by copying around view matrices
     struct Geometry {
         SkRect fDevOutside;
         SkRect fDevOutsideAssist;
         SkRect fDevInside;
         GrColor fColor;
         bool fMiterStroke;
+        bool fDegenerate;
     };
 
     static GrDrawBatch* Create(GrColor color, const SkMatrix& viewMatrix, const SkRect& devOutside,
                                const SkRect& devOutsideAssist, const SkRect& devInside,
-                               bool miterStroke) {
+                               bool miterStroke, bool degenerate) {
         return new AAStrokeRectBatch(color, viewMatrix, devOutside, devOutsideAssist, devInside,
-                                     miterStroke);
+                                     miterStroke, degenerate);
     }
 
     const char* name() const override { return "AAStrokeRect"; }
 
     void getInvariantOutputColor(GrInitInvariantOutput* out) const override {
         // When this is called on a batch, there is only one geometry bundle
         out->setKnownFourComponents(fGeoData[0].fColor);
     }
 
     void getInvariantOutputCoverage(GrInitInvariantOutput* out) const override {
         out->setUnknownSingleComponent();
     }
 
     SkSTArray<1, Geometry, true>* geoData() { return &fGeoData; }
 
 private:
     void onPrepareDraws(Target*) override;
     void initBatchTracker(const GrPipelineOptimizations&) override;
 
     AAStrokeRectBatch(GrColor color, const SkMatrix& viewMatrix, const SkRect& devOutside,
-                      const SkRect& devOutsideAssist, const SkRect& devInside, bool miterStroke)
+                      const SkRect& devOutsideAssist, const SkRect& devInside, bool miterStroke,
+                      bool degenerate)
         : INHERITED(ClassID()) {
         fBatch.fViewMatrix = viewMatrix;
         Geometry& geometry = fGeoData.push_back();
         geometry.fColor = color;
         geometry.fDevOutside = devOutside;
         geometry.fDevOutsideAssist = devOutsideAssist;
         geometry.fDevInside = devInside;
         geometry.fMiterStroke = miterStroke;
+        geometry.fDegenerate = degenerate;
 
         // If we have miterstroke then we inset devOutside and outset devOutsideAssist, so we need
         // the join for proper bounds
         fBounds = geometry.fDevOutside;
         fBounds.join(geometry.fDevOutsideAssist);
     }
 
 
     static const int kMiterIndexCnt = 3 * 24;
     static const int kMiterVertexCnt = 16;
@@ skipping 19 matching lines @@
     void generateAAStrokeRectGeometry(void* vertices,
                                       size_t offset,
                                       size_t vertexStride,
                                       int outerVertexNum,
                                       int innerVertexNum,
                                       GrColor color,
                                       const SkRect& devOutside,
                                       const SkRect& devOutsideAssist,
                                       const SkRect& devInside,
                                       bool miterStroke,
+                                      bool degenerate,
                                       bool tweakAlphaForCoverage) const;
 
     struct BatchTracker {
         SkMatrix fViewMatrix;
         GrColor fColor;
         bool fUsesLocalCoords;
         bool fColorIgnored;
         bool fCoverageIgnored;
         bool fMiterStroke;
         bool fCanTweakAlphaForCoverage;
@@ skipping 62 matching lines @@
         this->generateAAStrokeRectGeometry(vertices,
                                            i * verticesPerInstance * vertexStride,
                                            vertexStride,
                                            outerVertexNum,
                                            innerVertexNum,
                                            args.fColor,
                                            args.fDevOutside,
                                            args.fDevOutsideAssist,
                                            args.fDevInside,
                                            args.fMiterStroke,
+                                           args.fDegenerate,
                                            canTweakAlphaForCoverage);
     }
     helper.recordDraw(target);
 }
 
 const GrIndexBuffer* AAStrokeRectBatch::GetIndexBuffer(GrResourceProvider* resourceProvider,
                                                        bool miterStroke) {
 
     if (miterStroke) {
         static const uint16_t gMiterIndices[] = {
@@ skipping 120 matching lines @@
 void AAStrokeRectBatch::generateAAStrokeRectGeometry(void* vertices,
                                                      size_t offset,
                                                      size_t vertexStride,
                                                      int outerVertexNum,
                                                      int innerVertexNum,
                                                      GrColor color,
                                                      const SkRect& devOutside,
                                                      const SkRect& devOutsideAssist,
                                                      const SkRect& devInside,
                                                      bool miterStroke,
+                                                     bool degenerate,
                                                      bool tweakAlphaForCoverage) const {
     intptr_t verts = reinterpret_cast<intptr_t>(vertices) + offset;
 
     // We create vertices for four nested rectangles. There are two ramps from 0 to full
     // coverage, one on the exterior of the stroke and the other on the interior.
     // The following pointers refer to the four rects, from outermost to innermost.
     SkPoint* fan0Pos = reinterpret_cast<SkPoint*>(verts);
     SkPoint* fan1Pos = reinterpret_cast<SkPoint*>(verts + outerVertexNum * vertexStride);
     SkPoint* fan2Pos = reinterpret_cast<SkPoint*>(verts + 2 * outerVertexNum * vertexStride);
     SkPoint* fan3Pos = reinterpret_cast<SkPoint*>(verts +
@@ skipping 15 matching lines @@
     SkASSERT(inset >= 0);
 #else
     SkScalar inset = SK_ScalarHalf;
 #endif
 
     if (miterStroke) {
         // outermost
         set_inset_fan(fan0Pos, vertexStride, devOutside, -SK_ScalarHalf, -SK_ScalarHalf);
         // inner two
         set_inset_fan(fan1Pos, vertexStride, devOutside,  inset,  inset);
-        set_inset_fan(fan2Pos, vertexStride, devInside,  -inset, -inset);
-        // innermost
-        set_inset_fan(fan3Pos, vertexStride, devInside,   SK_ScalarHalf,  SK_ScalarHalf);
+        if (!degenerate) {
+            set_inset_fan(fan2Pos, vertexStride, devInside,  -inset, -inset);
+            // innermost
+            set_inset_fan(fan3Pos, vertexStride, devInside,   SK_ScalarHalf,  SK_ScalarHalf);
+        } else {

[robertphillips, 2015/09/21 17:12:44]

// When the interior rect has become degenerate ... ?

SkASSERT(devInside.fLeft == devInside.fRight);
SkASSERT(devInside.fTop == devInside.fBottom);

?

[joshualitt, 2015/09/21 19:51:25]

Acknowledged.

+            fan2Pos->setRectFan(devInside.fLeft, devInside.fTop,
+                                devInside.fRight, devInside.fBottom, vertexStride);
+            fan3Pos->setRectFan(devInside.fLeft, devInside.fTop,
+                                devInside.fRight, devInside.fBottom, vertexStride);
+        }
     } else {
         SkPoint* fan0AssistPos = reinterpret_cast<SkPoint*>(verts + 4 * vertexStride);
         SkPoint* fan1AssistPos = reinterpret_cast<SkPoint*>(verts +
                                                             (outerVertexNum + 4) *
                                                             vertexStride);
         // outermost
         set_inset_fan(fan0Pos, vertexStride, devOutside, -SK_ScalarHalf, -SK_ScalarHalf);
         set_inset_fan(fan0AssistPos, vertexStride, devOutsideAssist, -SK_ScalarHalf,
                       -SK_ScalarHalf);
         // outer one of the inner two
         set_inset_fan(fan1Pos, vertexStride, devOutside,  inset,  inset);
         set_inset_fan(fan1AssistPos, vertexStride, devOutsideAssist,  inset,  inset);
-        // inner one of the inner two
-        set_inset_fan(fan2Pos, vertexStride, devInside,  -inset, -inset);
-        // innermost
-        set_inset_fan(fan3Pos, vertexStride, devInside,   SK_ScalarHalf,  SK_ScalarHalf);
+        if (!degenerate) {
+            // inner one of the inner two
+            set_inset_fan(fan2Pos, vertexStride, devInside,  -inset, -inset);
+            // innermost
+            set_inset_fan(fan3Pos, vertexStride, devInside,   SK_ScalarHalf,  SK_ScalarHalf);
+        } else {

[robertphillips, 2015/09/21 17:12:44]

// When the interior rect has become degenerate ... ?

asserts ?

[joshualitt, 2015/09/21 19:51:25]

Acknowledged.

+            fan2Pos->setRectFan(devInside.fLeft, devInside.fTop,
+                                devInside.fRight, devInside.fBottom, vertexStride);
+            fan3Pos->setRectFan(devInside.fLeft, devInside.fTop,
+                                devInside.fRight, devInside.fBottom, vertexStride);
+        }
     }
 
     // Make verts point to vertex color and then set all the color and coverage vertex attrs
     // values. The outermost rect has 0 coverage
     verts += sizeof(SkPoint);
     for (int i = 0; i < outerVertexNum; ++i) {
         if (tweakAlphaForCoverage) {
             *reinterpret_cast<GrColor*>(verts + i * vertexStride) = 0;
         } else {
             *reinterpret_cast<GrColor*>(verts + i * vertexStride) = color;
             *reinterpret_cast<float*>(verts + i * vertexStride + sizeof(GrColor)) = 0;
         }
     }
 
     // scale is the coverage for the the inner two rects.
     int scale;

[robertphillips, 2015/09/21 17:12:44]

This hardens the inner/outer fan too 

[joshualitt, 2015/09/21 19:51:25]

Acknowledged.

-    if (inset < SK_ScalarHalf) {
+    if (inset < SK_ScalarHalf && !degenerate) {
         scale = SkScalarFloorToInt(512.0f * inset / (inset + SK_ScalarHalf));
         SkASSERT(scale >= 0 && scale <= 255);
     } else {
         scale = 0xff;
     }
 
     float innerCoverage = GrNormalizeByteToFloat(scale);
     GrColor scaledColor = (0xff == scale) ? color : SkAlphaMulQ(color, scale);
 
     verts += outerVertexNum * vertexStride;
     for (int i = 0; i < outerVertexNum + innerVertexNum; ++i) {
         if (tweakAlphaForCoverage) {
             *reinterpret_cast<GrColor*>(verts + i * vertexStride) = scaledColor;
         } else {
             *reinterpret_cast<GrColor*>(verts + i * vertexStride) = color;
             *reinterpret_cast<float*>(verts + i * vertexStride + sizeof(GrColor)) =
                     innerCoverage;
         }
     }
 
-    // The innermost rect has 0 coverage
+    // The innermost rect has 0 coverage, unless we are degenerate
     verts += (outerVertexNum + innerVertexNum) * vertexStride;
+    scale = 0;
+    if (degenerate) {
+        scale = 0xff;
+    }
     for (int i = 0; i < innerVertexNum; ++i) {
         if (tweakAlphaForCoverage) {
-            *reinterpret_cast<GrColor*>(verts + i * vertexStride) = 0;
+            *reinterpret_cast<GrColor*>(verts + i * vertexStride) = scale;
         } else {
             *reinterpret_cast<GrColor*>(verts + i * vertexStride) = color;
-            *reinterpret_cast<GrColor*>(verts + i * vertexStride + sizeof(GrColor)) = 0;
+            *reinterpret_cast<GrColor*>(verts + i * vertexStride + sizeof(GrColor)) = scale;
         }
     }
 }
 
 namespace GrAAStrokeRectBatch {
 
 GrDrawBatch* Create(GrColor color,
                     const SkMatrix& viewMatrix,
                     const SkRect& devOutside,
                     const SkRect& devOutsideAssist,
                     const SkRect& devInside,
-                    bool miterStroke) {
+                    bool miterStroke,
+                    bool degenerate) {
     return AAStrokeRectBatch::Create(color, viewMatrix, devOutside, devOutsideAssist, devInside,
-                                     miterStroke);
+                                     miterStroke, degenerate);
 }
 
 };
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 #ifdef GR_TEST_UTILS
 
 #include "GrBatchTest.h"
 
 DRAW_BATCH_TEST_DEFINE(AAStrokeRectBatch) {
     bool miterStroke = random->nextBool();
+    bool degenerate = random->nextBool();
 
     // Create mock stroke rect
     SkRect outside = GrTest::TestRect(random);
     SkScalar minDim = SkMinScalar(outside.width(), outside.height());
     SkScalar strokeWidth = minDim * 0.1f;
     SkRect outsideAssist = outside;
     outsideAssist.outset(strokeWidth, strokeWidth);
     SkRect inside = outside;
     inside.inset(strokeWidth, strokeWidth);
 
     GrColor color = GrRandomColor(random);
 
     return GrAAStrokeRectBatch::Create(color, GrTest::TestMatrix(random), outside, outsideAssist,
-                                       inside, miterStroke);
+                                       inside, degenerate, miterStroke);
 }
 
 #endif