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