1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
2  * This Source Code Form is subject to the terms of the Mozilla Public
3  * License, v. 2.0. If a copy of the MPL was not distributed with this
4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
5 
6 #ifndef GFX_READBACKPROCESSOR_H
7 #define GFX_READBACKPROCESSOR_H
8 
9 #include <stdint.h>                     // for uint64_t
10 #include "nsRect.h"                     // for mozilla::gfx::IntRect
11 #include "nsRegionFwd.h"                // for nsIntRegion
12 #include "nsTArray.h"                   // for nsTArray
13 
14 namespace mozilla {
15 namespace layers {
16 
17 class ContainerLayer;
18 class ReadbackLayer;
19 class PaintedLayer;
20 
21 class ReadbackProcessor {
22 public:
23   /**
24    * Called by the container before processing any child layers. Call this
25    * if any child layer might have changed in any way (other than content-only
26    * changes to layers other than ColorLayers and PaintedLayers).
27    *
28    * This method recomputes the relationship between ReadbackLayers and
29    * sibling layers, and dispatches changes to ReadbackLayers. Except that
30    * if a PaintedLayer needs its contents sent to some ReadbackLayer, we'll
31    * just record that internally and later the PaintedLayer should call
32    * GetPaintedLayerUpdates when it paints, to find out which rectangle needs
33    * to be sent, and the ReadbackLayer it needs to be sent to.
34    */
35   void BuildUpdates(ContainerLayer* aContainer);
36 
37   struct Update {
38     /**
39      * The layer a PaintedLayer should send its contents to.
40      */
41     ReadbackLayer* mLayer;
42     /**
43      * The rectangle of content that it should send, in the PaintedLayer's
44      * coordinate system. This rectangle is guaranteed to be in the PaintedLayer's
45      * visible region. Translate it to mLayer's coordinate system
46      * by adding mLayer->GetBackgroundLayerOffset().
47      */
48     gfx::IntRect      mUpdateRect;
49     /**
50      * The sequence counter value to use when calling DoUpdate
51      */
52     uint64_t       mSequenceCounter;
53   };
54   /**
55    * Appends any ReadbackLayers that need to be updated, and the rects that
56    * need to be updated, to aUpdates. Only need to call this for PaintedLayers
57    * that have been marked UsedForReadback().
58    * Each Update's mLayer's mBackgroundLayer will have been set to aLayer.
59    * If a PaintedLayer doesn't call GetPaintedLayerUpdates, then all the
60    * ReadbackLayers that needed data from that PaintedLayer will be marked
61    * as having unknown backgrounds.
62    * @param aUpdateRegion if non-null, this region is set to the union
63    * of the mUpdateRects.
64    */
65   void GetPaintedLayerUpdates(PaintedLayer* aLayer,
66                              nsTArray<Update>* aUpdates,
67                              nsIntRegion* aUpdateRegion = nullptr);
68 
69   ~ReadbackProcessor();
70 
71 protected:
72   void BuildUpdatesForLayer(ReadbackLayer* aLayer);
73 
74   nsTArray<Update> mAllUpdates;
75 };
76 
77 } // namespace layers
78 } // namespace mozilla
79 
80 #endif /* GFX_READBACKPROCESSOR_H */
81