Bug 935862 p3 - implement selective reflow for downloadable fonts. r=heycam

layout/base/nsPresContext.cpp

@@ -66,6 +66,7 @@
 #include "nsPIWindowRoot.h"
 #include "mozilla/Preferences.h"
 #include "gfxTextRun.h"
+#include "nsFontFaceUtils.h"
 
 // Needed for Start/Stop of Image Animation
 #include "imgIContainer.h"
@@ -2145,24 +2146,47 @@ nsPresContext::RebuildUserFontSet()
 }
 
 void
-nsPresContext::UserFontSetUpdated()
+nsPresContext::UserFontSetUpdated(gfxUserFontEntry* aUpdatedFont)
 {
   if (!mShell)
     return;
 
-  // Changes to the set of available fonts can cause updates to layout by:
-  //
-  //   1. Changing the font used for text, which changes anything that
-  //      depends on text measurement, including line breaking and
-  //      intrinsic widths, and any other parts of layout that depend on
-  //      font metrics.  This requires a style change reflow to update.
-  //
-  //   2. Changing the value of the 'ex' and 'ch' units in style data,
-  //      which also depend on font metrics.  Updating this information
-  //      requires rebuilding the rule tree from the top, avoiding the
-  //      reuse of cached data even when no style rules have changed.
+  bool usePlatformFontList = true;
+#if defined(MOZ_WIDGET_GTK) || defined(MOZ_WIDGET_QT)
+  usePlatformFontList = false;
+#endif
 
-  PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW, eRestyle_ForceDescendants);
+  // xxx - until the Linux platform font list is always used, use full
+  // restyle to force updates with gfxPangoFontGroup usage
+  // Note: this method is called without a font when rules in the userfont set
+  // are updated, which may occur during reflow as a result of the lazy
+  // initialization of the userfont set. It would be better to avoid a full
+  // restyle but until this method is only called outside of reflow, schedule a
+  // full restyle in these cases.
+  if (!usePlatformFontList || !aUpdatedFont) {
+    PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW, eRestyle_ForceDescendants);
+    return;
+  }
+
+  // Special case - if either the 'ex' or 'ch' units are used, these
+  // depend upon font metrics. Updating this information requires
+  // rebuilding the rule tree from the top, avoiding the reuse of cached
+  // data even when no style rules have changed.
+
+  if (UsesExChUnits()) {
+    // xxx - dbaron said this should work but get ex/ch related reftest failures
+    // PostRebuildAllStyleDataEvent(nsChangeHint(0), eRestyle_ForceDescendants);
+    PostRebuildAllStyleDataEvent(NS_STYLE_HINT_REFLOW, eRestyle_ForceDescendants);
+    return;
+  }
+
+  // Iterate over the frame tree looking for frames associated with the
+  // downloadable font family in question. If a frame's nsStyleFont has
+  // the name, check the font group associated with the metrics to see if
+  // it contains that specific font (i.e. the one chosen within the family
+  // given the weight, width, and slant from the nsStyleFont). If it does,
+  // mark that frame dirty and skip inspecting its descendants.
+  nsFontFaceUtils::MarkDirtyForFontChange(mShell->GetRootFrame(), aUpdatedFont);
 }
 
 FontFaceSet*

layout/base/nsPresContext.h

@@ -56,6 +56,7 @@ class nsICSSPseudoComparator;
 struct nsStyleBackground;
 struct nsStyleBorder;
 class nsIRunnable;
+class gfxUserFontEntry;
 class gfxUserFontSet;
 class gfxTextPerfMetrics;
 struct nsFontFaceRuleContainer;
@@ -890,7 +891,7 @@ public:
   // Should be called whenever the set of fonts available in the user
   // font set changes (e.g., because a new font loads, or because the
   // user font set is changed and fonts become unavailable).
-  void UserFontSetUpdated();
+  void UserFontSetUpdated(gfxUserFontEntry* aUpdatedFont = nullptr);
 
   gfxMissingFontRecorder *MissingFontRecorder() { return mMissingFonts; }
   void NotifyMissingFonts();

layout/style/moz.build

@@ -141,6 +141,7 @@ UNIFIED_SOURCES += [
     'nsDOMCSSRGBColor.cpp',
     'nsDOMCSSValueList.cpp',
     'nsFontFaceLoader.cpp',
+    'nsFontFaceUtils.cpp',
     'nsHTMLCSSStyleSheet.cpp',
     'nsHTMLStyleSheet.cpp',
     'nsLayoutStylesheetCache.cpp',

layout/style/nsFontFaceLoader.cpp

@@ -121,7 +121,7 @@ nsFontFaceLoader::LoadTimerCallback(nsITimer* aTimer, void* aClosure)
     NS_ASSERTION(ctx, "userfontset doesn't have a presContext?");
     if (ctx) {
       loader->mFontFaceSet->IncrementGeneration();
-      ctx->UserFontSetUpdated();
+      ctx->UserFontSetUpdated(loader->GetUserFontEntry());
       LOG(("userfonts (%p) timeout reflow\n", loader));
     }
   }
@@ -193,7 +193,7 @@ nsFontFaceLoader::OnStreamComplete(nsIStreamLoader* aLoader,
   if (fontUpdate) {
     // Update layout for the presence of the new font.  Since this is
     // asynchronous, reflows will coalesce.
-    ctx->UserFontSetUpdated();
+    ctx->UserFontSetUpdated(mUserFontEntry);
     LOG(("userfonts (%p) reflow\n", this));
   }
 

layout/style/nsFontFaceLoader.h

@@ -45,6 +45,7 @@ public:
   static nsresult CheckLoadAllowed(nsIPrincipal* aSourcePrincipal,
                                    nsIURI* aTargetURI,
                                    nsISupports* aContext);
+  gfxUserFontEntry* GetUserFontEntry() const { return mUserFontEntry; }
 
 protected:
   virtual ~nsFontFaceLoader();

layout/style/nsFontFaceUtils.cpp

@@ -0,0 +1,116 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+// vim:cindent:ts=2:et:sw=2:
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gfxUserFontSet.h"
+#include "nsFontFaceUtils.h"
+#include "nsFontMetrics.h"
+#include "nsIFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsPlaceholderFrame.h"
+#include "nsTArray.h"
+
+static bool StyleContextContainsFont(nsStyleContext* aStyleContext,
+                                     const gfxUserFontSet* aUserFontSet,
+                                     const gfxUserFontEntry* aFont)
+{
+  // if the font is null, simply check to see whether fontlist includes
+  // downloadable fonts
+  if (!aFont) {
+    const FontFamilyList& fontlist =
+      aStyleContext->StyleFont()->mFont.fontlist;
+    return aUserFontSet->ContainsUserFontSetFonts(fontlist);
+  }
+
+  // first, check if the family name is in the fontlist
+  const nsString& familyName = aFont->FamilyName();
+  if (!aStyleContext->StyleFont()->mFont.fontlist.Contains(familyName)) {
+    return false;
+  }
+
+  // family name is in the fontlist, check to see if the font group
+  // associated with the frame includes the specific userfont
+  nsRefPtr<nsFontMetrics> fm;
+  nsLayoutUtils::GetFontMetricsForStyleContext(aStyleContext,
+                                               getter_AddRefs(fm),
+                                               1.0f);
+
+  if (fm->GetThebesFontGroup()->ContainsUserFont(aFont)) {
+    return true;
+  }
+
+  return false;
+}
+
+static bool
+FrameUsesFont(nsIFrame* aFrame, const gfxUserFontEntry* aFont)
+{
+  // check the style context of the frame
+  gfxUserFontSet* ufs = aFrame->PresContext()->GetUserFontSet();
+  if (StyleContextContainsFont(aFrame->StyleContext(), ufs, aFont)) {
+    return true;
+  }
+
+  // check additional style contexts
+  int32_t contextIndex = 0;
+  for (nsStyleContext* extraContext;
+       (extraContext = aFrame->GetAdditionalStyleContext(contextIndex));
+       ++contextIndex) {
+    if (StyleContextContainsFont(extraContext, ufs, aFont)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/* static */ void
+nsFontFaceUtils::MarkDirtyForFontChange(nsIFrame* aSubtreeRoot,
+                                        const gfxUserFontEntry* aFont)
+{
+  nsAutoTArray<nsIFrame*, 4> subtrees;
+  subtrees.AppendElement(aSubtreeRoot);
+
+  nsIPresShell* ps = aSubtreeRoot->PresContext()->PresShell();
+
+  // check descendants, iterating over subtrees that may include
+  // additional subtrees associated with placeholders
+  do {
+    nsIFrame* subtreeRoot = subtrees.ElementAt(subtrees.Length() - 1);
+    subtrees.RemoveElementAt(subtrees.Length() - 1);
+
+    // Check all descendants to see if they use the font
+    nsAutoTArray<nsIFrame*, 32> stack;
+    stack.AppendElement(subtreeRoot);
+
+    do {
+      nsIFrame* f = stack.ElementAt(stack.Length() - 1);
+      stack.RemoveElementAt(stack.Length() - 1);
+
+      // if this frame uses the font, mark its descendants dirty
+      // and skip checking its children
+      if (FrameUsesFont(f, aFont)) {
+        ps->FrameNeedsReflow(f, nsIPresShell::eStyleChange, NS_FRAME_IS_DIRTY);
+      } else {
+        if (f->GetType() == nsGkAtoms::placeholderFrame) {
+          nsIFrame* oof = nsPlaceholderFrame::GetRealFrameForPlaceholder(f);
+          if (!nsLayoutUtils::IsProperAncestorFrame(subtreeRoot, oof)) {
+            // We have another distinct subtree we need to mark.
+            subtrees.AppendElement(oof);
+          }
+        }
+
+        nsIFrame::ChildListIterator lists(f);
+        for (; !lists.IsDone(); lists.Next()) {
+          nsFrameList::Enumerator childFrames(lists.CurrentList());
+          for (; !childFrames.AtEnd(); childFrames.Next()) {
+            nsIFrame* kid = childFrames.get();
+            stack.AppendElement(kid);
+          }
+        }
+      }
+    } while (!stack.IsEmpty());
+  } while (!subtrees.IsEmpty());
+}

layout/style/nsFontFaceUtils.h

@@ -0,0 +1,23 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+// vim:cindent:ts=2:et:sw=2:
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* helper utilities for working with downloadable fonts */
+
+#ifndef nsFontFaceUtils_h_
+#define nsFontFaceUtils_h_
+
+class gfxUserFontEntry;
+class nsIFrame;
+
+class nsFontFaceUtils
+{
+public:
+  // mark dirty frames affected by a downloadable font
+  static void MarkDirtyForFontChange(nsIFrame* aSubtreeRoot,
+                                     const gfxUserFontEntry* aFont);
+};
+
+#endif /* !defined(nsFontFaceUtils_h_) */