Implement Media Queries, part 4: infrastructure for dynamic change handling at the pres context level. (Bug 156716) r+sr=bzbarsky

layout/base/nsPresContext.cpp

@@ -20,6 +20,7 @@
  * the Initial Developer. All Rights Reserved.
  *
  * Contributor(s):
+ *   L. David Baron <dbaron@dbaron.org>, Mozilla Corporation
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either of the GNU General Public License Version 2 or later (the "GPL"),
@@ -728,6 +729,7 @@ nsPresContext::PreferenceChanged(const char* aPrefName)
       nscoord height = NSToCoordRound(oldHeightDevPixels*AppUnitsPerDevPixel());
       vm->SetWindowDimensions(width, height);
 
+      MediaFeatureValuesChanged(PR_TRUE);
       RebuildAllStyleData(NS_STYLE_HINT_REFLOW);
     }
     return;
@@ -1163,6 +1165,7 @@ nsPresContext::SetFullZoom(float aZoom)
   mFullZoom = aZoom;
   GetViewManager()->SetWindowDimensions(NSToCoordRound(oldWidthDevPixels * AppUnitsPerDevPixel()),
                                         NSToCoordRound(oldHeightDevPixels * AppUnitsPerDevPixel()));
+  MediaFeatureValuesChanged(PR_TRUE);
   RebuildAllStyleData(NS_STYLE_HINT_REFLOW);
 
   mSupressResizeReflow = PR_FALSE;
@@ -1445,6 +1448,39 @@ nsPresContext::PostRebuildAllStyleDataEvent()
   mShell->FrameConstructor()->PostRebuildAllStyleDataEvent();
 }
 
+void
+nsPresContext::MediaFeatureValuesChanged(PRBool aCallerWillRebuildStyleData)
+{
+  mPendingMediaFeatureValuesChanged = PR_FALSE;
+  if (mShell->StyleSet()->MediumFeaturesChanged(this) &&
+      !aCallerWillRebuildStyleData) {
+    RebuildAllStyleData(nsChangeHint(0));
+  }
+}
+
+void
+nsPresContext::PostMediaFeatureValuesChangedEvent()
+{
+  if (!mPendingMediaFeatureValuesChanged) {
+    nsCOMPtr<nsIRunnable> ev =
+      new nsRunnableMethod<nsPresContext>(this,
+                         &nsPresContext::HandleMediaFeatureValuesChangedEvent);
+    if (NS_SUCCEEDED(NS_DispatchToCurrentThread(ev))) {
+      mPendingMediaFeatureValuesChanged = PR_TRUE;
+    }
+  }
+}
+
+void
+nsPresContext::HandleMediaFeatureValuesChangedEvent()
+{
+  // Null-check mShell in case the shell has been destroyed (and the
+  // event is the only thing holding the pres context alive).
+  if (mPendingMediaFeatureValuesChanged && mShell) {
+    MediaFeatureValuesChanged(PR_FALSE);
+  }
+}
+
 void
 nsPresContext::SetPaginatedScrolling(PRBool aPaginated)
 {

layout/base/nsPresContext.h

@@ -20,6 +20,7 @@
  * the Initial Developer. All Rights Reserved.
  *
  * Contributor(s):
+ *   L. David Baron <dbaron@dbaron.org>, Mozilla Corporation
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either of the GNU General Public License Version 2 or later (the "GPL"),
@@ -209,6 +210,14 @@ public:
   void RebuildAllStyleData(nsChangeHint aExtraHint);
   void PostRebuildAllStyleDataEvent();
 
+  void MediaFeatureValuesChanged(PRBool aCallerWillRebuildStyleData);
+  void PostMediaFeatureValuesChangedEvent();
+  NS_HIDDEN_(void) HandleMediaFeatureValuesChangedEvent();
+  void FlushPendingMediaFeatureValuesChanged() {
+    if (mPendingMediaFeatureValuesChanged)
+      MediaFeatureValuesChanged(PR_FALSE);
+  }
+
   /**
    * Access compatibility mode for this context.  This is the same as
    * our document's compatibility mode.
@@ -421,7 +430,10 @@ public:
    * Set the currently visible area. The units for r are standard
    * nscoord units (as scaled by the device context).
    */
-  void SetVisibleArea(const nsRect& r) { mVisibleArea = r; }
+  void SetVisibleArea(const nsRect& r) {
+    mVisibleArea = r;
+    PostMediaFeatureValuesChangedEvent();
+  }
 
   /**
    * Return true if this presentation context is a paginated
@@ -889,6 +901,7 @@ protected:
   unsigned              mPrefScrollbarSide : 2;
   unsigned              mPendingSysColorChanged : 1;
   unsigned              mPendingThemeChanged : 1;
+  unsigned              mPendingMediaFeatureValuesChanged : 1;
   unsigned              mPrefChangePendingNeedsReflow : 1;
   unsigned              mRenderedPositionVaryingContent : 1;
 

layout/base/nsPresShell.cpp

@@ -4555,6 +4555,8 @@ PresShell::DoFlushPendingNotifications(mozFlushType aType,
     // Process pending restyles, since any flush of the presshell wants
     // up-to-date style data.
     if (!mIsDestroying) {
+      mPresContext->FlushPendingMediaFeatureValuesChanged();
+
       mFrameConstructor->ProcessPendingRestyles();
     }
 

layout/style/nsMediaFeatures.cpp

@@ -224,6 +224,15 @@ GetGrid(nsPresContext* aPresContext, nsCSSValue& aResult)
     return NS_OK;
 }
 
+/*
+ * Adding new media features requires (1) adding the new feature to this
+ * array, with appropriate entries (and potentially any new code needed
+ * to support new types in these entries and (2) ensuring that either
+ * nsPresContext::MediaFeatureValuesChanged or
+ * nsPresContext::PostMediaFeatureValuesChangedEvent is called when the
+ * value that would be returned by the entry's mGetter changes.
+ */
+
 /* static */ const nsMediaFeature
 nsMediaFeatures::features[] = {
     {