Treat calls to CanvasRenderingContext2D.clearRect as operations that clear the canvas

Source/platform/graphics/skia/OpaqueRegionSkia.h

-/*
- * Copyright (c) 2012, Google Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met:
- *
- *     * Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *     * Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following disclaimer
- * in the documentation and/or other materials provided with the
- * distribution.
- *     * Neither the name of Google Inc. nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#ifndef OpaqueRegionSkia_h
-#define OpaqueRegionSkia_h
-
-#include "platform/PlatformExport.h"
-#include "platform/geometry/IntRect.h"
-
-#include "SkBitmap.h"
-#include "SkCanvas.h"
-#include "SkPaint.h"
-#include "SkPoint.h"
-#include "SkRect.h"
-
-namespace blink {
-class GraphicsContext;
-
-// This class is an encapsulation of functionality for GraphicsContext, and its methods are mirrored
-// there for the outside world. It tracks paints and computes what area will be opaque.
-class PLATFORM_EXPORT OpaqueRegionSkia FINAL {
-public:
-    OpaqueRegionSkia();
-
-    // The resulting opaque region as a single rect.
-    IntRect asRect() const;
-
-    void pushCanvasLayer(const SkPaint*);
-    void popCanvasLayer(const GraphicsContext*);
-
-    void setImageMask(const SkRect& imageOpaqueRect);
-
-    enum DrawType {
-        FillOnly,
-        FillOrStroke
-    };
-
-    void didDrawRect(const GraphicsContext*, const SkRect&, const SkPaint&, const SkBitmap* sourceBitmap);
-    void didDrawPath(const GraphicsContext*, const SkPath&, const SkPaint&);
-    void didDrawPoints(const GraphicsContext*, SkCanvas::PointMode, int numPoints, const SkPoint[], const SkPaint&);
-    void didDrawBounded(const GraphicsContext*, const SkRect&, const SkPaint&);
-    void didDrawUnbounded(const GraphicsContext*, const SkPaint&, DrawType);
-
-    struct CanvasLayerState {
-        CanvasLayerState()
-            : hasImageMask(false)
-            , opaqueRect(SkRect::MakeEmpty())
-        { }
-
-        SkPaint paint;
-
-        // An image mask is being applied to the layer.
-        bool hasImageMask;
-        // The opaque area in the image mask.
-        SkRect imageOpaqueRect;
-
-        SkRect opaqueRect;
-    };
-
-    void reset();
-
-private:
-    void didDraw(const GraphicsContext*, const SkRect&, const SkPaint&, const SkBitmap* sourceBitmap, bool fillsBounds, DrawType);
-    void applyOpaqueRegionFromLayer(const GraphicsContext*, const SkRect& layerOpaqueRect, const SkPaint&);
-    void markRectAsOpaque(const SkRect&);
-    void markRectAsNonOpaque(const SkRect&);
-    void markAllAsNonOpaque();
-
-    SkRect& currentTrackingOpaqueRect();
-
-    SkRect m_opaqueRect;
-
-    Vector<CanvasLayerState, 3> m_canvasLayerStack;
-};
-
-}
-#endif // OpaqueRegionSkia_h