cc: Consolidate the analysis_canvas operations

skia/ext/analysis_canvas.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/trace_event.h"
 #include "skia/ext/analysis_canvas.h"
 #include "third_party/skia/include/core/SkDevice.h"
 #include "third_party/skia/include/core/SkDraw.h"
 #include "third_party/skia/include/core/SkRRect.h"
+#include "third_party/skia/src/core/SkRasterClip.h"
 #include "ui/gfx/rect_conversions.h"
 
 namespace {
 
 // FIXME: Arbitrary number. Requires tuning & experimentation.
 // Probably requires per-platform tuning; N10 average draw call takes
 // 25x as long as Z620.
 const int gPictureCostThreshold = 1000;
 
+static bool isSolidColorPaint(const SkPaint& paint) {
+  SkXfermode::Mode xferMode;
+
+  // NULL turns into kSrcOver mode.

[Tom Hudson, 2013/02/25 17:16:04]

This comment is unclear, since NULL is nowhere in sight.

+  SkXfermode::AsMode(paint.getXfermode(), &xferMode);
+
+  // Paint is solid color if the following holds:
+  // - Alpha is 1.0, style is fill, and there are no special effects
+  // - Xfer mode is either kSrc or kSrcOver (kSrcOver is equivalent
+  //   to kSrc if source alpha is 1.0, which is already checked).
+  return (paint.getAlpha() == 255 &&
+          !paint.getShader() &&
+          !paint.getLooper() &&
+          !paint.getMaskFilter() &&
+          !paint.getColorFilter() &&
+          paint.getStyle() == SkPaint::kFill_Style &&
+          (xferMode == SkXfermode::kSrc_Mode ||
+           xferMode == SkXfermode::kSrcOver_Mode));
 }
 
+} // namespace
+
 namespace skia {
 
 AnalysisDevice::AnalysisDevice(const SkBitmap& bm)
   : INHERITED(bm)
-  , estimatedCost_(0) {
+  , estimatedCost_(0)
+  , isForcedNotSolid_(false)
+  , isSolidColor_(false) {
 
 }
 
 AnalysisDevice::~AnalysisDevice() {
-
 }
 
 int AnalysisDevice::getEstimatedCost() const {
   return estimatedCost_;
 }
 
+bool AnalysisDevice::getColorIfSolid(SkColor* color) const {
+  if (isSolidColor_)
+    *color = color_;
+  return isSolidColor_;
+}
+
+bool AnalysisDevice::isTransparent() const {
+  //TODO(vmpstr) implement
+  return false;
+}
+
+void AnalysisDevice::setForceNotSolid(bool flag) {
+  isForcedNotSolid_ = flag;
+  if (isForcedNotSolid_)
+    isSolidColor_ = false;
+}
+
 void AnalysisDevice::clear(SkColor color) {
-    ++estimatedCost_;
+  ++estimatedCost_;
+  if (!isForcedNotSolid_ && SkColorGetA(color) == 255) {
+    isSolidColor_ = true;
+    color_ = color;
+  }
+  else {
+    isSolidColor_ = false;
+  }
 }
 
 void AnalysisDevice::drawPaint(const SkDraw&, const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawPoints(const SkDraw&, SkCanvas::PointMode mode,
                           size_t count, const SkPoint[],
                           const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
-void AnalysisDevice::drawRect(const SkDraw&, const SkRect& r,
+void AnalysisDevice::drawRect(const SkDraw& draw, const SkRect& rect,
                         const SkPaint& paint) {
   // FIXME: if there's a pending image decode & resize, more expensive
   if (paint.getMaskFilter()) {
     estimatedCost_ += 300;
   }
   ++estimatedCost_;
+
+  if (isForcedNotSolid_)
+    return;
+
+  SkRect clipRect = SkRect::Make(draw.fRC->getBounds());
+  SkRect bitmapRect = SkRect::MakeWH(width(), height());
+
+  // This bitmap is solid if and only if the following holds.
+  // Note that this might be overly conservative:
+  // - Paint is solid color
+  // - Clip rect is an actual rectangle.
+  // - The rect we're drawing contains the clip rect.
+  //   That is, all of clip rect will be colored by the rect.
+  // - Clip rect contains the bitmap rect.
+  //   That is, we're not clipping to a portion of this bitmap.

[Tom Hudson, 2013/02/25 17:16:04]

You mention "bitmap", but when we're on the border of Skia "canvas" might be a
better term, both in docs and in naming the variable, since it isn't necessarily
backed by a bitmap and we commonly speak of drawing bitmaps TO devices.

Another way to phrase the introduction would be to say that you're testing to
see if this drawRect() is equivalent to a clear()?

+  if (isSolidColorPaint(paint) &&
+      draw.fRC->isRect() &&
+      rect.contains(clipRect) &&
+      clipRect.contains(bitmapRect)) {
+    isSolidColor_ = true;
+    color_ = paint.getColor();
+  }
+  else {
+    isSolidColor_ = false;
+  }
 }
 
 void AnalysisDevice::drawOval(const SkDraw&, const SkRect& oval,
                         const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawPath(const SkDraw&, const SkPath& path,
                         const SkPaint& paint,
                         const SkMatrix* prePathMatrix ,
                         bool pathIsMutable ) {
   // On Z620, every antialiased path costs us about 300us.
   // We've only seen this in practice on filled paths, but
   // we expect it to apply to all path stroking modes.
   if (paint.getMaskFilter()) {
     estimatedCost_ += 300;
   }
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawBitmap(const SkDraw&, const SkBitmap& bitmap,
                           const SkIRect* srcRectOrNull,
                           const SkMatrix& matrix, const SkPaint& paint)
                           {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawSprite(const SkDraw&, const SkBitmap& bitmap,
                           int x, int y, const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawBitmapRect(const SkDraw&, const SkBitmap&,
                               const SkRect* srcOrNull, const SkRect& dst,
                               const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 
 void AnalysisDevice::drawText(const SkDraw&, const void* text, size_t len,
                         SkScalar x, SkScalar y, const SkPaint& paint)
                         {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawPosText(const SkDraw& draw, const void* text, size_t len,
                            const SkScalar pos[], SkScalar constY,
                            int scalarsPerPos, const SkPaint& paint) {
   // FIXME: On Z620, every glyph cache miss costs us about 10us.
   // We don't have a good mechanism for predicting glyph cache misses.
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawTextOnPath(const SkDraw&, const void* text, size_t len,
                               const SkPath& path, const SkMatrix* matrix,
                               const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 #ifdef SK_BUILD_FOR_ANDROID
 void AnalysisDevice::drawPosTextOnPath(const SkDraw& draw, const void* text,
                                  size_t len,
                                  const SkPoint pos[], const SkPaint& paint,
                                  const SkPath& path, const SkMatrix* matrix)
                                  {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 #endif
 
 void AnalysisDevice::drawVertices(const SkDraw&, SkCanvas::VertexMode,
                             int vertexCount,
                             const SkPoint verts[], const SkPoint texs[],
                             const SkColor colors[], SkXfermode* xmode,
                             const uint16_t indices[], int indexCount,
                             const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 void AnalysisDevice::drawDevice(const SkDraw&, SkDevice*, int x, int y,
                           const SkPaint&) {
   ++estimatedCost_;
+  isSolidColor_ = false;
 }
 
 
 
 
 AnalysisCanvas::AnalysisCanvas(AnalysisDevice* device)
-  : INHERITED(device) {
-
+  : INHERITED(device)
+  , saveDepth_(0) {
 }
 
 AnalysisCanvas::~AnalysisCanvas() {
 }
 
 
 bool AnalysisCanvas::isCheap() const {
   return getEstimatedCost() < gPictureCostThreshold;
 }
 
+bool AnalysisCanvas::getColorIfSolid(SkColor* color) const {
+  return (static_cast<AnalysisDevice*>(getDevice()))->getColorIfSolid(color);
+}
+
+bool AnalysisCanvas::isTransparent() const {
+  return (static_cast<AnalysisDevice*>(getDevice()))->isTransparent();
+}
+
 int AnalysisCanvas::getEstimatedCost() const {
   return (static_cast<AnalysisDevice*>(getDevice()))->getEstimatedCost();
 }
 
-
 bool AnalysisCanvas::clipRect(const SkRect& rect, SkRegion::Op op,
                         bool doAA) {
   return INHERITED::clipRect(rect, op, doAA);
 }
 
 bool AnalysisCanvas::clipPath(const SkPath& path, SkRegion::Op op,
                         bool doAA) {
   return INHERITED::clipRect(path.getBounds(), op, doAA);
 }
 
 bool AnalysisCanvas::clipRRect(const SkRRect& rrect, SkRegion::Op op,
                          bool doAA) {
   return INHERITED::clipRect(rrect.getBounds(), op, doAA);
 }
 
-int AnalysisCanvas::saveLayer(const SkRect* bounds, const SkPaint*, 
+int AnalysisCanvas::saveLayer(const SkRect* bounds, const SkPaint* paint, 
                               SkCanvas::SaveFlags flags) {
+  if (paint && !isSolidColorPaint(*paint))
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(true);
+  ++saveDepth_;
+
   // Actually saving a layer here could cause a new bitmap to be created
   // and real rendering to occur.
-  int count = SkCanvas::save(flags);
+  int count = INHERITED::save(flags);
   if (bounds) {
     INHERITED::clipRectBounds(bounds, flags, NULL);
   }
   return count;
 }
 
+void AnalysisCanvas::restore() {
+  INHERITED::restore();
+  if (--saveDepth_ == 0)
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(false);

[Tom Hudson, 2013/02/25 17:16:04]

This looks really conservative: if we ever save a non-solid layer, we assume
we're non-solid until we pop all the way back to the root?

+}
+
 }  // namespace skia