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));
 }
 
+} // namespace
+
 namespace skia {
 
 AnalysisDevice::AnalysisDevice(const SkBitmap& bm)
   : INHERITED(bm)
-  , estimatedCost_(0) {
+  , estimatedCost_(0)
+  , isForcedNotSolid_(false)
+  , isForcedNotTransparent_(false)
+  , isSolidColor_(false)
+  , isTransparent_(false) {
 
 }
 
 AnalysisDevice::~AnalysisDevice() {
-

[Tom Hudson, 2013/02/27 14:49:36]

Nit: Is this whitespace change dictated by the Chromium style guide, or
accidental?

 }
 
 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_;
+
+  SkRect drawBitmapRect;
+  draw.fBitmap->getBounds(&drawBitmapRect);
+  SkRect clipRect = SkRect::Make(draw.fRC->getBounds());
+  SkRect canvasRect = SkRect::MakeWH(width(), height());
+  SkRect deviceRect;
+  draw.fMatrix->mapRect(&deviceRect, rect);
+
+
+  // This draw is equivalent to clear(), 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.
+  bool isFullQuad = (draw.fRC->isRect() &&
+                     deviceRect.contains(clipRect) &&
+                     clipRect.contains(canvasRect) &&
+                     drawBitmapRect.contains(canvasRect));
+
+  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 (isFullQuad &&
+      !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) &&
+      isFullQuad) {
+    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&,
-                              const SkRect* srcOrNull, const SkRect& dst,
+void AnalysisDevice::drawBitmapRect(const SkDraw& draw, const SkBitmap&,
+                              const SkRect* srcOrNull, const SkRect& rect,

[Tom Hudson, 2013/02/27 14:49:36]

Nit: I think you've changed this parameter name from the Skia convention to the
CC convention? I'm constitutionally opposed to the loss of information; there
are two rects in play here.

                               const SkPaint& paint) {
   ++estimatedCost_;
+  isSolidColor_ = false;
+
+  SkRect drawBitmapRect;
+  draw.fBitmap->getBounds(&drawBitmapRect);
+  SkRect clipRect = SkRect::Make(draw.fRC->getBounds());
+  SkRect bitmapRect = SkRect::MakeWH(width(), height());
+  SkRect deviceRect;
+  draw.fMatrix->mapRect(&deviceRect, rect);
+
+  // This draw is equivalent to clear(), if the following conditions hold:

[Tom Hudson, 2013/02/27 14:49:36]

Both of these clauses are duplicated from drawRect(); can we move these to a
helper function?

(Or we could call drawRect() directly until the cost estimation function is
sophisticated enough to need them to diverge...)

+  // - 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.
+  bool isFullQuad = (draw.fRC->isRect() &&
+                     deviceRect.contains(clipRect) &&
+                     clipRect.contains(bitmapRect) &&
+                     drawBitmapRect.contains(bitmapRect));
+
+  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 (isFullQuad &&
+      !isForcedNotTransparent_ &&
+      xferMode == SkXfermode::kClear_Mode) {
+    isTransparent_ = true;
+  }
+  else if (paint.getAlpha() != 0 ||
+           xferMode != SkXfermode::kSrc_Mode) {
+    isTransparent_ = 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)
+  , savedLayerStackSize_(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::save(SkCanvas::SaveFlags flags) {
+  INHERITED::save(flags);
+}
+
+int AnalysisCanvas::saveLayer(const SkRect* bounds, const SkPaint* paint, 
                               SkCanvas::SaveFlags flags) {
+  // 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.

[Tom Hudson, 2013/02/27 14:49:36]

Thanks for adding these explanations.

+  if ((paint && !isSolidColorPaint(*paint)) ||
+      (bounds && !bounds->contains(
+          SkRect::MakeWH(getDevice()->width(), getDevice()->height()))))
+    (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)
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotTransparent(true);
+
+  ++savedLayerStackSize_;
+
   // 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 (--savedLayerStackSize_ == 0) {
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotSolid(false);
+    (static_cast<AnalysisDevice*>(getDevice()))->setForceNotTransparent(false);
+  }
+}
+
 }  // namespace skia