layout/base/ActiveLayerTracker.h

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #ifndef ACTIVELAYERTRACKER_H_
   6 #define ACTIVELAYERTRACKER_H_
   7
   8 #include "nsCSSProperty.h"
   9
  10 class nsIFrame;
  11 class nsIContent;
  12 class nsDisplayListBuilder;
  13
  14 namespace mozilla {
  15
  16 /**
  17  * This class receives various notifications about style changes and content
  18  * changes that affect layerization decisions, and implements the heuristics
  19  * that drive those decisions. It manages per-frame state to support those
  20  * heuristics.
  21  */
  22 class ActiveLayerTracker {
  23 public:
  24   static void Shutdown();
  25
  26   /*
  27    * We track style changes to selected styles:
  28    *   eCSSProperty_transform
  29    *   eCSSProperty_opacity
  30    *   eCSSProperty_left, eCSSProperty_top, eCSSProperty_right, eCSSProperty_bottom
  31    * and use that information to guess whether style changes are animated.
  32    */
  33
  34   /**
  35    * Notify aFrame's style property as having changed due to a restyle,
  36    * and therefore possibly wanting an active layer to render that style.
  37    * Any such marking will time out after a short period.
  38    * @param aProperty the property that has changed
  39    */
  40   static void NotifyRestyle(nsIFrame* aFrame, nsCSSProperty aProperty);
  41   /**
  42    * Notify aFrame's left/top/right/bottom properties as having (maybe)
  43    * changed due to a restyle, and therefore possibly wanting an active layer
  44    * to render that style. Any such marking will time out after a short period.
  45    */
  46   static void NotifyOffsetRestyle(nsIFrame* aFrame);
  47   /**
  48    * Mark aFrame as being known to have an animation of aProperty.
  49    * Any such marking will time out after a short period.
  50    */
  51   static void NotifyAnimated(nsIFrame* aFrame, nsCSSProperty aProperty);
  52   /**
  53    * Notify that a property in the inline style rule of aFrame's element
  54    * has been modified.
  55    * This notification is incomplete --- not all modifications to inline
  56    * style will trigger this.
  57    */
  58   static void NotifyInlineStyleRuleModified(nsIFrame* aFrame, nsCSSProperty aProperty);
  59   /**
  60    * Return true if aFrame's aProperty style should be considered as being animated
  61    * for pre-rendering.
  62    */
  63   static bool IsStyleMaybeAnimated(nsIFrame* aFrame, nsCSSProperty aProperty);
  64   /**
  65    * Return true if aFrame's aProperty style should be considered as being animated
  66    * for constructing active layers.
  67    */
  68   static bool IsStyleAnimated(nsDisplayListBuilder* aBuilder, nsIFrame* aFrame,
  69                               nsCSSProperty aProperty);
  70   /**
  71    * Return true if any of aFrame's offset property styles should be considered
  72    * as being animated for constructing active layers.
  73    */
  74   static bool IsOffsetOrMarginStyleAnimated(nsIFrame* aFrame);
  75   /**
  76    * Transfer the LayerActivity property to the frame's content node when the
  77    * frame is about to be destroyed so that layer activity can be tracked
  78    * throughout reframes of an element. Only call this when aFrame is the
  79    * primary frame of aContent.
  80    */
  81   static void TransferActivityToContent(nsIFrame* aFrame, nsIContent* aContent);
  82   /**
  83    * Transfer the LayerActivity property back to the content node's primary
  84    * frame after the frame has been created.
  85    */
  86   static void TransferActivityToFrame(nsIContent* aContent, nsIFrame* aFrame);
  87
  88   /*
  89    * We track modifications to the content of certain frames (i.e. canvas frames)
  90    * and use that to make layering decisions.
  91    */
  92
  93   /**
  94    * Mark aFrame's content as being active. This marking will time out after
  95    * a short period.
  96    */
  97   static void NotifyContentChange(nsIFrame* aFrame);
  98   /**
  99    * Return true if this frame's content is still marked as active.
 100    */
 101   static bool IsContentActive(nsIFrame* aFrame);
 102 };
 103
 104 }
 105
 106 #endif /* ACTIVELAYERTRACKER_H_ */