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;
+
+  // getXfermode can return a NULL, but that is handled
+  // gracefully by AsMode (NULL turns into kSrcOver mode).
+  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));
 }
 
+static bool isFullQuad(const SkDraw& draw,
+                       const SkRect& canvasRect,
+                       const SkRect& drawnRect) {
+
+  // If the transform results in a non-axis aligned
+  // rect, then be conservative and return false.
+  if (!draw.fMatrix->rectStaysRect())
+    return false;
+
+  SkRect drawBitmapRect;
+  draw.fBitmap->getBounds(&drawBitmapRect);
+  SkRect clipRect = SkRect::Make(draw.fRC->getBounds());
+  SkRect deviceRect;
+  draw.fMatrix->mapRect(&deviceRect, drawnRect);
+
+  // The drawn rect covers the full canvas, if the following conditions hold:
+  // - Clip rect is an actual rectangle.
+  // - The rect we're drawing (post-transform) contains the clip rect.
+  //   That is, all of clip rect will be colored by the rect.
+  // - Clip rect contains the canvas rect.
+  //   That is, we're not clipping to a portion of this canvas.
+  // - The bitmap into which the draw call happens is at least as
+  //   big as the canvas rect
+  return draw.fRC->isRect() &&

[Justin Novosad, 2013/03/06 15:24:43]

You can remove test on draw.fRC->isRect() since we know it always returns true
due to the complex clip hack.

+         deviceRect.contains(clipRect) &&
+         clipRect.contains(canvasRect) &&
+         drawBitmapRect.contains(canvasRect);
+}
+
+} // namespace
+
 namespace skia {
 
 AnalysisDevice::AnalysisDevice(const SkBitmap& bm)
   : INHERITED(bm)
-  , estimatedCost_(0) {
+  , estimatedCost_(0)
+  , isForcedNotSolid_(false)
+  , isForcedNotTransparent_(false)
+  , isSolidColor_(false)
+  , isTransparent_(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 {
+  return isTransparent_;
+}
+
+void AnalysisDevice::setForceNotSolid(bool flag) {
+  isForcedNotSolid_ = flag;
+  if (isForcedNotSolid_)
+    isSolidColor_ = false;
+}
+
+void AnalysisDevice::setForceNotTransparent(bool flag) {
+  isForcedNotTransparent_ = flag;
+  if (isForcedNotTransparent_)
+    isTransparent_ = false;
+}
+
 void AnalysisDevice::clear(SkColor color) {
-    ++estimatedCost_;
+  ++estimatedCost_;
+
+  isTransparent_ = (!isForcedNotTransparent_ && SkColorGetA(color) == 0);
+
+  if (!isForcedNotSolid_ && SkColorGetA(color) == 255) {
+    isSolidColor_ = true;
+    color_ = color;
+  }
+  else {
+    isSolidColor_ = false;
+  }
 }
 
 void AnalysisDevice::drawPaint(const SkDraw&, const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = false;
 }
 
 void AnalysisDevice::drawPoints(const SkDraw&, SkCanvas::PointMode mode,
                           size_t count, const SkPoint[],
                           const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = 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_;
+
+  bool doesCoverCanvas = isFullQuad(draw,
+                                    SkRect::MakeWH(width(), height()),
+                                    rect);
+
+  SkXfermode::Mode xferMode;
+  SkXfermode::AsMode(paint.getXfermode(), &xferMode);
+
+  // This canvas will become transparent if the following holds:
+  // - The quad is a full tile quad
+  // - We're not in "forced not transparent" mode
+  // - Transfer mode is clear (0 color, 0 alpha)
+  //
+  // If the paint alpha is not 0, or if the transfrer mode is
+  // not src, then this canvas will not be transparent.
+  //
+  // In all other cases, we keep the current transparent value
+  if (doesCoverCanvas &&
+      !isForcedNotTransparent_ &&
+      xferMode == SkXfermode::kClear_Mode) {
+    isTransparent_ = true;
+  }
+  else if (paint.getAlpha() != 0 ||
+           xferMode != SkXfermode::kSrc_Mode) {
+    isTransparent_ = false;
+  }
+
+  // This bitmap is solid if and only if the following holds.
+  // Note that this might be overly conservative:
+  // - We're not in "forced not solid" mode
+  // - Paint is solid color
+  // - The quad is a full tile quad
+  if (!isForcedNotSolid_ &&
+      isSolidColorPaint(paint) &&
+      doesCoverCanvas) {
+    isSolidColor_ = true;
+    color_ = paint.getColor();
+  }
+  else {
+    isSolidColor_ = false;
+  }
 }
 
 void AnalysisDevice::drawOval(const SkDraw&, const SkRect& oval,
                         const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = 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;
+  isTransparent_ = false;
 }
 
 void AnalysisDevice::drawBitmap(const SkDraw&, const SkBitmap& bitmap,
                           const SkIRect* srcRectOrNull,
-                          const SkMatrix& matrix, const SkPaint& paint)
-                          {
+                          const SkMatrix& matrix, const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = false;
 }
 
 void AnalysisDevice::drawSprite(const SkDraw&, const SkBitmap& bitmap,
                           int x, int y, const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = false;
 }
 
-void AnalysisDevice::drawBitmapRect(const SkDraw&, const SkBitmap&,
+void AnalysisDevice::drawBitmapRect(const SkDraw& draw, const SkBitmap&,
                               const SkRect* srcOrNull, const SkRect& dst,
                               const SkPaint& paint) {
   ++estimatedCost_;
+
+  // Call drawRect to determine transparency,
+  // but reset solid color to false.
+  drawRect(draw, dst, paint);
+  isSolidColor_ = false;
 }
 
 
 void AnalysisDevice::drawText(const SkDraw&, const void* text, size_t len,
-                        SkScalar x, SkScalar y, const SkPaint& paint)
-                        {
+                        SkScalar x, SkScalar y, const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = 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;
+  isTransparent_ = false;
 }
 
 void AnalysisDevice::drawTextOnPath(const SkDraw&, const void* text, size_t len,
                               const SkPath& path, const SkMatrix* matrix,
                               const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = 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)
-                                 {
+                                 const SkPath& path, const SkMatrix* matrix) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = 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;
+  isTransparent_ = false;
 }
 
 void AnalysisDevice::drawDevice(const SkDraw&, SkDevice*, int x, int y,
                           const SkPaint&) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+  isTransparent_ = false;
 }
 
 
 
-
 AnalysisCanvas::AnalysisCanvas(AnalysisDevice* device)
-  : INHERITED(device) {
-
+  : INHERITED(device)
+  , savedStackSize_(0)
+  , forceNotSolidStackLevel_(0)
+  , forceNotTransparentStackLevel_(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) {
+  // clipPaths can make our calls to isFullQuad invalid (ie have false
+  // positives). As a precaution, force the setting to be non-solid
+  // and non-transparent until we pop this 
+  if (forceNotSolidStackLevel_ == 0) {

[Justin Novosad, 2013/03/06 15:24:43]

There is a bug here due to '0' being ambiguous (0 could mean that we called
clipPath at stack level 0). Instead you could test that forceNotSolid is
currently set to false.
You should have a unit test verifies this.  Something like:
clipPath
saveLayer
clipPath
restore
fill canvas with solid color
EXPECT_FALSE(canvas.getColorIfSolid());

I think the current implementation would fail this test.

+    forceNotSolidStackLevel_ = savedStackSize_;
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(true);
+  }
+  if (forceNotTransparentStackLevel_ == 0) {

[Justin Novosad, 2013/03/06 15:24:43]

Bug

+    forceNotTransparentStackLevel_ = savedStackSize_;
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotTransparent(true);
+  }
+
   return INHERITED::clipRect(path.getBounds(), op, doAA);
 }
 
 bool AnalysisCanvas::clipRRect(const SkRRect& rrect, SkRegion::Op op,
                          bool doAA) {
+  // clipRRect can make our calls to isFullQuad invalid (ie have false
+  // positives). As a precaution, force the setting to be non-solid
+  // and non-transparent until we pop this 
+  if (forceNotSolidStackLevel_ == 0) {

[Justin Novosad, 2013/03/06 15:24:43]

Bug

+    forceNotSolidStackLevel_ = savedStackSize_;
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(true);
+  }
+  if (forceNotTransparentStackLevel_ == 0) {

[Justin Novosad, 2013/03/06 15:24:43]

Bug

+    forceNotTransparentStackLevel_ = savedStackSize_;
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotTransparent(true);
+  }
+
   return INHERITED::clipRect(rrect.getBounds(), op, doAA);
 }
 
-int AnalysisCanvas::saveLayer(const SkRect* bounds, const SkPaint*, 
+int AnalysisCanvas::save(SkCanvas::SaveFlags flags) {
+  INHERITED::save(flags);
+  ++savedStackSize_;
+}
+
+int AnalysisCanvas::saveLayer(const SkRect* bounds, const SkPaint* paint, 
                               SkCanvas::SaveFlags flags) {
+  ++savedStackSize_;
+
+  // If after we draw to the saved layer, we have to blend with the current
+  // layer, then we can conservatively say that the canvas will not be of
+  // solid color.
+  if ((paint && !isSolidColorPaint(*paint)) ||
+      (bounds && !bounds->contains(
+          SkRect::MakeWH(getDevice()->width(), getDevice()->height())))) {
+    if (forceNotSolidStackLevel_ == 0) {
+      forceNotSolidStackLevel_ = savedStackSize_;
+      (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(true);
+    }
+  }
+
+  // If after we draw to the save layer, we have to blend with the current
+  // layer using any part of the current layer's alpha, then we can
+  // conservatively say that the canvas will not be transparent.
+  SkXfermode::Mode xferMode = SkXfermode::kSrc_Mode;
+  if (paint)
+    SkXfermode::AsMode(paint->getXfermode(), &xferMode);
+  if (xferMode != SkXfermode::kSrc_Mode) {
+    if (forceNotTransparentStackLevel_ == 0) {
+      forceNotTransparentStackLevel_ = savedStackSize_;
+      (static_cast<AnalysisDevice*>(getDevice()))->setForceNotTransparent(true);
+    }
+  }
+
   // 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();
+
+  --savedStackSize_;

[Justin Novosad, 2013/03/06 15:24:43]

Need to gracefully handle the case of a restore that does not have a matching
save, or at least assert.

+  if (savedStackSize_ < forceNotSolidStackLevel_) {
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(false);
+    forceNotSolidStackLevel_ = 0;
+  }
+  if (savedStackSize_ < forceNotTransparentStackLevel_) {
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotTransparent(false);
+    forceNotTransparentStackLevel_ = 0;
+  }
+}
+
 }  // namespace skia