test picture-ops for savelayer

src/core/SkRecordOpts.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRecordOpts.h"
 
 #include "SkRecordPattern.h"
 #include "SkRecords.h"
 #include "SkTDArray.h"
+#include "SkXfermode.h"
 
 using namespace SkRecords;
 
 // Most of the optimizations in this file are pattern-based.  These are all defined as structs with:
 //   - a Match typedef
 //   - a bool onMatch(SkRceord*, Match*, int begin, int end) method,
 //     which returns true if it made changes and false if not.
 
 // Run a pattern-based optimization once across the SkRecord, returning true if it made any changes.
 // It looks for spans which match Pass::Match, and when found calls onMatch() with that pattern,
@@ skipping 141 matching lines @@
     }
 };
 void SkRecordNoopSaveRestores(SkRecord* record) {
     SaveOnlyDrawsRestoreNooper onlyDraws;
     SaveNoDrawsRestoreNooper noDraws;
 
     // Run until they stop changing things.
     while (apply(&onlyDraws, record) || apply(&noDraws, record));
 }
 
+static bool effectively_srcover(const SkPaint* paint) {
+    if (!paint) {
+        return true;
+    }
+    SkXfermode* mode = paint->getXfermode();
+    if (SkXfermode::IsMode(mode, SkXfermode::kSrcOver_Mode)) {
+        return true;
+    }
+    // src-mode with opaque and no effects (which might change opaqueness) is ok too.
+    return !paint->getShader() && !paint->getColorFilter() && !paint->getImageFilter() &&
+           0xFF == paint->getAlpha() && SkXfermode::IsMode(mode, SkXfermode::kSrc_Mode);
+}
+
 // For some SaveLayer-[drawing command]-Restore patterns, merge the SaveLayer's alpha into the
 // draw, and no-op the SaveLayer and Restore.
 struct SaveLayerDrawRestoreNooper {
     typedef Pattern<Is<SaveLayer>, IsDraw, Is<Restore>> Match;
 
     bool onMatch(SkRecord* record, Match* match, int begin, int end) {
         if (match->first<SaveLayer>()->backdrop) {
             // can't throw away the layer if we have a backdrop
             return false;
         }
 
         // A SaveLayer's bounds field is just a hint, so we should be free to ignore it.
         SkPaint* layerPaint = match->first<SaveLayer>()->paint;
-        if (nullptr == layerPaint) {
+        SkPaint* drawPaint = match->second<SkPaint>();
+
+        if (nullptr == layerPaint && effectively_srcover(drawPaint)) {
             // There wasn't really any point to this SaveLayer at all.
             return KillSaveLayerAndRestore(record, begin);
         }
 
-        SkPaint* drawPaint = match->second<SkPaint>();
         if (drawPaint == nullptr) {
             // We can just give the draw the SaveLayer's paint.
             // TODO(mtklein): figure out how to do this clearly
             return false;
         }
 
         if (!fold_opacity_layer_color_to_paint(*layerPaint, false /*isSaveLayer*/, drawPaint)) {
             return false;
         }
 
@@ skipping 85 matching lines @@
 }
 
 void SkRecordOptimize2(SkRecord* record) {
     multiple_set_matrices(record);
     SkRecordNoopSaveRestores(record);
     SkRecordNoopSaveLayerDrawRestores(record);
     SkRecordMergeSvgOpacityAndFilterLayers(record);
 
     record->defrag();
 }