ccpr: Preserve fill rules for cached paths

Fixes a bug where even-odd fill rule was not being preserved on paths
that were reused from a stashed fp16 coverage count atlas.

Bug: skia:8782
Change-Id: I6698498a6f4c8df8eff10b19beb80e49663a577c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/218047
Reviewed-by: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

gm/gm.h

@@ -152,7 +152,7 @@ namespace skiagm {
         bool getControls(SkMetaData* controls) { return this->onGetControls(controls); }
         void setControls(const SkMetaData& controls) { this->onSetControls(controls); }
 
-        virtual void modifyGrContextOptions(GrContextOptions* options);
+        virtual void modifyGrContextOptions(GrContextOptions*);
 
     protected:
         virtual void onOnceBeforeDraw();

gm/preservefillrule.cpp

@@ -0,0 +1,148 @@
+/*
+ * Copyright 2019 Google LLC.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "gm/gm.h"
+
+#include "include/core/SkPath.h"
+#include "include/gpu/GrContext.h"
+#include "include/gpu/GrContextOptions.h"
+#include "src/gpu/GrContextPriv.h"
+#include "src/gpu/GrDrawingManager.h"
+#include "src/gpu/GrRenderTargetContext.h"
+#include "src/gpu/ccpr/GrCCPathCache.h"
+#include "src/gpu/ccpr/GrCoverageCountingPathRenderer.h"
+#include "tools/ToolUtils.h"
+
+namespace skiagm {
+
+#define ERR_MSG_ASSERT(COND) \
+    do { \
+        if (!(COND)) { \
+            errorMsg->printf("preservefillrule.cpp(%i): assert(%s)", \
+                             __LINE__, #COND); \
+            return DrawResult::kFail; \
+        } \
+    } while (false)
+
+
+/**
+ * This test ensures that the ccpr path cache preserves fill rules properly, both in the case where
+ * we copy paths into a8 literal coverage atlases, as well as in the case where we just reuse a
+ * stashed fp16 coverage count atlas.
+ */
+class PreserveFillRuleGM : public GpuGM {
+public:
+    // fStarSize affects whether ccpr copies the paths to an a8 literal coverage atlas, or just
+    // leaves them stashed in an fp16 coverage count atlas. The threshold for copying to a8 is
+    // currently 256x256 total pixels copied. If this ever changes, there is code in onDraw that
+    // will detect the unexpected behavior and draw a failure message.
+    PreserveFillRuleGM(bool literalCoverageAtlas)
+            : fLiteralCoverageAtlas(literalCoverageAtlas)
+            , fStarSize((fLiteralCoverageAtlas) ? 200 : 20) {
+    }
+
+private:
+    SkString onShortName() override {
+        SkString name("preservefillrule");
+        name += (fLiteralCoverageAtlas) ? "_big" : "_little";
+        return name;
+    }
+    SkISize onISize() override { return SkISize::Make(fStarSize * 2, fStarSize * 2); }
+
+    void modifyGrContextOptions(GrContextOptions* ctxOptions) override {
+        ctxOptions->fGpuPathRenderers = GpuPathRenderers::kCoverageCounting;
+        ctxOptions->fAllowPathMaskCaching = true;
+    }
+
+    DrawResult onDraw(GrContext* ctx, GrRenderTargetContext* rtc, SkCanvas* canvas,
+                      SkString* errorMsg) override {
+        using CoverageType = GrCCAtlas::CoverageType;
+
+        auto* ccpr = ctx->priv().drawingManager()->getCoverageCountingPathRenderer();
+        if (!ccpr) {
+            errorMsg->set("ccpr only");
+            return DrawResult::kSkip;
+        }
+
+        auto pathCache = ccpr->testingOnly_getPathCache();
+        if (!pathCache) {
+            errorMsg->set("ccpr is not in caching mode. "
+                          "Are you using viewer? Launch with \"--cachePathMasks true\".");
+            return DrawResult::kFail;
+        }
+
+        auto starRect = SkRect::MakeWH(fStarSize, fStarSize);
+        SkPath star7_winding = ToolUtils::make_star(starRect, 7);
+        star7_winding.setFillType(SkPath::kWinding_FillType);
+
+        SkPath star7_evenOdd = star7_winding;
+        star7_evenOdd.transform(SkMatrix::MakeTrans(0, fStarSize));
+        star7_evenOdd.setFillType(SkPath::kEvenOdd_FillType);
+
+        SkPath star5_winding = ToolUtils::make_star(starRect, 5);
+        star5_winding.transform(SkMatrix::MakeTrans(fStarSize, 0));
+        star5_winding.setFillType(SkPath::kWinding_FillType);
+
+        SkPath star5_evenOdd = star5_winding;
+        star5_evenOdd.transform(SkMatrix::MakeTrans(0, fStarSize));
+        star5_evenOdd.setFillType(SkPath::kEvenOdd_FillType);
+
+        SkPaint paint;
+        paint.setColor(SK_ColorGREEN);
+        paint.setAntiAlias(true);
+
+        for (int i = 0; i < 3; ++i) {
+            canvas->clear(SK_ColorWHITE);
+            canvas->drawPath(star7_winding, paint);
+            canvas->drawPath(star7_evenOdd, paint);
+            canvas->drawPath(star5_winding, paint);
+            canvas->drawPath(star5_evenOdd, paint);
+            rtc->flush(SkSurface::BackendSurfaceAccess::kNoAccess, GrFlushInfo());
+
+            // Ensure the path cache is behaving in such a way that we are actually testing what we
+            // think we are.
+            int numCachedPaths = 0;
+            for (GrCCPathCacheEntry* entry : pathCache->testingOnly_getLRU()) {
+                if (0 == i) {
+                    // We don't cache an atlas on the first hit.
+                    ERR_MSG_ASSERT(!entry->cachedAtlas());
+                } else {
+                    // The stars should be cached in an atlas now.
+                    ERR_MSG_ASSERT(entry->cachedAtlas());
+
+                    CoverageType atlasCoverageType = entry->cachedAtlas()->coverageType();
+                    if (i < 2) {
+                        // We never copy to an a8 atlas before the second hit.
+                        ERR_MSG_ASSERT(CoverageType::kFP16_CoverageCount == atlasCoverageType);
+                    } else if (fLiteralCoverageAtlas) {
+                        // Verify fStarSize is large enough that the paths got copied to an a8
+                        // atlas.
+                        ERR_MSG_ASSERT(CoverageType::kA8_LiteralCoverage == atlasCoverageType);
+                    } else {
+                        // Verify fStarSize is small enough that the paths did *NOT* get copied to
+                        // an a8 atlas.
+                        ERR_MSG_ASSERT(CoverageType::kFP16_CoverageCount == atlasCoverageType);
+                    }
+                }
+                ++numCachedPaths;
+            }
+            // Verify all 4 paths are tracked by the path cache.
+            ERR_MSG_ASSERT(4 == numCachedPaths);
+        }
+
+        return DrawResult::kOk;
+    }
+
+private:
+    const bool fLiteralCoverageAtlas;
+    const int fStarSize;
+};
+
+DEF_GM( return new PreserveFillRuleGM(true); )
+DEF_GM( return new PreserveFillRuleGM(false); )
+
+}

gn/gm.gni

@@ -279,6 +279,7 @@ gm_sources = [
   "$_gm/poly2poly.cpp",
   "$_gm/polygonoffset.cpp",
   "$_gm/polygons.cpp",
+  "$_gm/preservefillrule.cpp",
   "$_gm/postercircle.cpp",
   "$_gm/quadpaths.cpp",
   "$_gm/radial_gradient_precision.cpp",

src/gpu/ccpr/GrCCDrawPathsOp.cpp

@@ -358,8 +358,8 @@ void GrCCDrawPathsOp::SingleDraw::setupResources(
 #endif
             op->recordInstance(fCacheEntry->cachedAtlas()->getOnFlushProxy(),
                                resources->nextPathInstanceIdx());
-            resources->appendDrawPathInstance().set(*fCacheEntry, fCachedMaskShift,
-                                                    SkPMColor4f_toFP16(fColor));
+            resources->appendDrawPathInstance().set(
+                    *fCacheEntry, fCachedMaskShift, SkPMColor4f_toFP16(fColor), doEvenOddFill);
             return;
         }
     }

src/gpu/ccpr/GrCCPathProcessor.cpp

@@ -166,8 +166,8 @@ void GrCCPathProcessor::Impl::onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) {
     // find an octagon that circumscribes the (bloated) path.
     GrGLSLVertexBuilder* v = args.fVertBuilder;
 
-    // Are we clockwise (positive wind, nonzero fill), or counter-clockwise (negative wind,
-    // even/odd fill)?
+    // Are we clockwise? (Positive wind => nonzero fill rule.)
+    // Or counter-clockwise? (negative wind => even/odd fill rule.)
     v->codeAppendf("float wind = sign(devbounds.z - devbounds.x);");
 
     // Find our reference corner from the device-space bounding box.

src/gpu/ccpr/GrCCPathProcessor.h

@@ -44,10 +44,8 @@ public:
         SkIVector fDevToAtlasOffset;  // Translation from device space to location in atlas.
         uint64_t fColor;  // Color always stored as 4 x fp16
 
-        void set(const GrOctoBounds&, const SkIVector& devToAtlasOffset, uint64_t,
-                 DoEvenOddFill = DoEvenOddFill::kNo);
-        void set(const GrCCPathCacheEntry&, const SkIVector& shift, uint64_t,
-                 DoEvenOddFill = DoEvenOddFill::kNo);
+        void set(const GrOctoBounds&, const SkIVector& devToAtlasOffset, uint64_t, DoEvenOddFill);
+        void set(const GrCCPathCacheEntry&, const SkIVector& shift, uint64_t, DoEvenOddFill);
     };
 
     GR_STATIC_ASSERT(4 * 12 == sizeof(Instance));