Fix ClipMaskManager's SW-fallback logic (take 2)

src/gpu/GrClipMaskManager.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrClipMaskManager.h"
 #include "GrCaps.h"
 #include "GrDrawContext.h"
@@ skipping 28 matching lines @@
 
     SkIRect domainTexels = SkIRect::MakeWH(devBound.width(), devBound.height());
     return GrTextureDomainEffect::Create(result,
                                          mat,
                                          GrTextureDomain::MakeTexelDomain(result, domainTexels),
                                          GrTextureDomain::kDecal_Mode,
                                          GrTextureParams::kNone_FilterMode,
                                          kDevice_GrCoordSet);
 }
 
+// Does the path in 'element' require SW rendering? If so, return true (and,
+// optionally, set 'prOut' to NULL. If not, return false (and, optionally, set
+// 'prOut' to the non-SW path renderer that will do the job).
 static bool path_needs_SW_renderer(GrContext* context,
                                    const GrPipelineBuilder& pipelineBuilder,
                                    const SkMatrix& viewMatrix,
-                                   const SkPath& origPath,
-                                   const GrStrokeInfo& stroke,
-                                   bool doAA) {
-    // the gpu alpha mask will draw the inverse paths as non-inverse to a temp buffer
-    SkTCopyOnFirstWrite<SkPath> path(origPath);
-    if (path->isInverseFillType()) {
-        path.writable()->toggleInverseFillType();
+                                   const Element* element,
+                                   GrPathRenderer** prOut,
+                                   bool tryStencilFirst) {
+    if (Element::kRect_Type == element->getType()) {
+        // rects can always be drawn directly w/o using the software path
+        // TODO: skip rrects once we're drawing them directly.
+        if (prOut) {
+            *prOut = nullptr;
+        }
+        return false;
+    } else {
+        // We shouldn't get here with an empty clip element.
+        SkASSERT(Element::kEmpty_Type != element->getType());
+
+        // the gpu alpha mask will draw the inverse paths as non-inverse to a temp buffer
+        SkPath path;
+        element->asPath(&path);
+        if (path.isInverseFillType()) {
+            path.toggleInverseFillType();
+        }
+        GrStrokeInfo stroke(SkStrokeRec::kFill_InitStyle);
+    
+        GrPathRendererChain::DrawType type;
+        
+        if (tryStencilFirst) {
+            type = element->isAA()
+                            ? GrPathRendererChain::kStencilAndColorAntiAlias_DrawType
+                            : GrPathRendererChain::kStencilAndColor_DrawType;
+        } else {
+            type = element->isAA()
+                            ? GrPathRendererChain::kColorAntiAlias_DrawType
+                            : GrPathRendererChain::kColor_DrawType;    
+        }
+    
+        // the 'false' parameter disallows use of the SW path renderer
+        GrPathRenderer* pr = context->getPathRenderer(&pipelineBuilder, viewMatrix, path,
+                                                      stroke, false, type);
+        if (tryStencilFirst && !pr) {
+            // If the path can't be stenciled, createAlphaClipMask falls back to color rendering
+            // it into a temporary buffer. If that fails then SW is truly required.
+            type = element->isAA()
+                            ? GrPathRendererChain::kColorAntiAlias_DrawType
+                            : GrPathRendererChain::kColor_DrawType;  
+
+            pr = context->getPathRenderer(&pipelineBuilder, viewMatrix, path, stroke, false, type);
+        }
+
+        if (prOut) {
+            *prOut = pr;
+        }
+        return SkToBool(!pr);
     }
-    // last (false) parameter disallows use of the SW path renderer
-    GrPathRendererChain::DrawType type = doAA ?
-                                         GrPathRendererChain::kColorAntiAlias_DrawType :
-                                         GrPathRendererChain::kColor_DrawType;
-
-    return nullptr == context->getPathRenderer(&pipelineBuilder, viewMatrix, *path, stroke,
-                                               false, type);
 }
 
 GrClipMaskManager::GrClipMaskManager(GrDrawTarget* drawTarget)
     : fDrawTarget(drawTarget)
     , fClipMode(kIgnoreClip_StencilClipMode) {
 }
 
 GrContext* GrClipMaskManager::getContext() { return fDrawTarget->cmmAccess().context(); }
 
 /*
  * This method traverses the clip stack to see if the GrSoftwarePathRenderer
  * will be used on any element. If so, it returns true to indicate that the
  * entire clip should be rendered in SW and then uploaded en masse to the gpu.
  */
 bool GrClipMaskManager::useSWOnlyPath(const GrPipelineBuilder& pipelineBuilder,
                                       const SkVector& clipToMaskOffset,
                                       const GrReducedClip::ElementList& elements) {
     // TODO: generalize this function so that when
     // a clip gets complex enough it can just be done in SW regardless
     // of whether it would invoke the GrSoftwarePathRenderer.
-    GrStrokeInfo stroke(SkStrokeRec::kFill_InitStyle);
 
     // Set the matrix so that rendered clip elements are transformed to mask space from clip
     // space.
     SkMatrix translate;
     translate.setTranslate(clipToMaskOffset);
 
     for (GrReducedClip::ElementList::Iter iter(elements.headIter()); iter.get(); iter.next()) {
         const Element* element = iter.get();
-        // rects can always be drawn directly w/o using the software path
-        // Skip rrects once we're drawing them directly.
-        if (Element::kRect_Type != element->getType()) {
-            SkPath path;
-            element->asPath(&path);
-            if (path_needs_SW_renderer(this->getContext(), pipelineBuilder, translate,
-                                       path, stroke, element->isAA())) {
-                return true;
-            }
+
+        SkRegion::Op op = element->getOp();
+        bool invert = element->isInverseFilled();
+        bool tryStencilFirst = invert || 
+                               SkRegion::kIntersect_Op == op ||
+                               SkRegion::kReverseDifference_Op == op;
+
+        if (path_needs_SW_renderer(this->getContext(), pipelineBuilder, translate,
+                                   element, nullptr, tryStencilFirst)) {
+            return true;
         }
     }
     return false;
 }
 
 bool GrClipMaskManager::getAnalyticClipProcessor(const GrReducedClip::ElementList& elements,
                                                  bool abortIfAA,
                                                  SkVector& clipToRTOffset,
                                                  const SkRect* drawBounds,
                                                  const GrFragmentProcessor** resultFP) {
@@ skipping 203 matching lines @@
                                                       initialState,
                                                       elements,
                                                       clipToMaskOffset,
                                                       clipSpaceIBounds));
         } else {
             result.reset(this->createAlphaClipMask(genID,
                                                    initialState,
                                                    elements,
                                                    clipToMaskOffset,
                                                    clipSpaceIBounds));
+            // If createAlphaClipMask fails it means useSWOnlyPath has a bug
+            SkASSERT(result);
         }
 
         if (result) {
             // The mask's top left coord should be pinned to the rounded-out top left corner of
             // clipSpace bounds. We determine the mask's position WRT to the render target here.
             SkIRect rtSpaceMaskBounds = clipSpaceIBounds;
             rtSpaceMaskBounds.offset(-clip.origin());
             out->fClipCoverageFP.reset(create_fp_for_mask(result, rtSpaceMaskBounds));
             this->setPipelineBuilderStencil(pipelineBuilder, ars);
             return true;
@@ skipping 776 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 
 void GrClipMaskManager::adjustPathStencilParams(const GrStencilAttachment* stencilAttachment,
                                                 GrStencilSettings* settings) {
     if (stencilAttachment) {
         int stencilBits = stencilAttachment->bits();
         this->adjustStencilParams(settings, fClipMode, stencilBits);
     }
 }