text: /*
   * 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 RegionTracker_h
  #define RegionTracker_h
  
  #include "platform/PlatformExport.h"
  #include "platform/geometry/IntRect.h"
  #include "third_party/skia/include/core/SkBitmap.h"
  #include "third_party/skia/include/core/SkCanvas.h"
  #include "third_party/skia/include/core/SkPaint.h"
  #include "third_party/skia/include/core/SkPoint.h"
  #include "third_party/skia/include/core/SkRect.h"
  
  namespace blink {
  class GraphicsContext;
  
  enum RegionTrackingMode {
      TrackOpaqueRegion,
      TRackOverwriteRegion
  };
  
  // 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 RegionTracker final {
  public:
      RegionTracker();
  
      // 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 RegionType {
          Opaque,
          Overwrite
      };
  
      // Set this to true to track regions that occlude the destination instead of only regions that produce opaque pixels.
      void setTrackedRegionType(RegionType type) { m_trackedRegionType = type; }
  
      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;
      RegionType m_trackedRegionType;
  
      Vector<CanvasLayerState, 3> m_canvasLayerStack;
  };
  
  } // namespace blink
  
  #endif // RegionTracker_h
  