Raster PictureLayerTiling with fractional translation

cc/playback/raster_source.h

 // Copyright 2014 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.
 
 #ifndef CC_PLAYBACK_RASTER_SOURCE_H_
 #define CC_PLAYBACK_RASTER_SOURCE_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <vector>
 
 #include "base/macros.h"
 #include "cc/base/cc_export.h"
 #include "cc/debug/rendering_stats_instrumentation.h"
 #include "cc/playback/recording_source.h"
 #include "skia/ext/analysis_canvas.h"
 #include "third_party/skia/include/core/SkPicture.h"
 
 namespace cc {
 class DisplayItemList;
 class DrawImage;
 class ImageDecodeController;
+class ScaleTranslate2d;
 
 class CC_EXPORT RasterSource : public base::RefCountedThreadSafe<RasterSource> {
  public:
   struct CC_EXPORT PlaybackSettings {
     PlaybackSettings();
 
     // If set to true, this indicates that the canvas has already been
     // rasterized into. This means that the canvas cannot be cleared safely.
     bool playback_to_shared_canvas;
 
     // If set to true, none of the images will be rasterized.
     bool skip_images;
 
     // If set to true, we will use an image hijack canvas, which enables
     // compositor image caching.
     bool use_image_hijack_canvas;
   };
 
   static scoped_refptr<RasterSource> CreateFromRecordingSource(
       const RecordingSource* other,
       bool can_use_lcd_text);
 
-  // TODO(trchen): Deprecated.
+  // Helper function to apply a few common operations before passing the canvas
+  // to the shorter version. This is useful for rastering into tiles.
+  // canvas is expected to be backed by a tile, with a default state.
+  // contents_transform will be applied to the display list, rastering the list
+  // into the "content space".
+  // canvas_bitmap_rect defines the extent of the tile in the content space,
+  // i.e. contents in the rect will be cropped and translated onto the canvas.
+  // canvas_playback_rect defines the damange rect in the content space.

[enne (OOO), 2016/08/29 20:21:19]

It's true that the canvas_playback_rect is the damage rect, but for the purposes
of this function I think it's better to define it as the subset of the recording
that should be rastered.

   void PlaybackToCanvas(SkCanvas* canvas,
                         const gfx::Rect& canvas_bitmap_rect,
                         const gfx::Rect& canvas_playback_rect,
-                        float contents_scale,
+                        const ScaleTranslate2d& contents_transform,
                         const PlaybackSettings& settings) const;
 
   // Raster this RasterSource into the given canvas. Canvas states such as
   // CTM and clip region will be respected. This function will replace pixels
   // in the clip region without blending. It is assumed that existing pixels
   // may be uninitialized and will be cleared before playback.
   //
   // Virtual for testing.
   //
   // Note that this should only be called after the image decode controller has
@@ skipping 104 matching lines @@
   void RasterCommon(SkCanvas* canvas, SkPicture::AbortCallback* callback) const;
 
   void PrepareForPlaybackToCanvas(SkCanvas* canvas) const;
 
   DISALLOW_COPY_AND_ASSIGN(RasterSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_RASTER_SOURCE_H_