bug 825504 - fix gfxPangoFontGroup::FindFamilyNameAt for user fonts, to resolve MathML fonts breakage. r=roc

gfx/thebes/gfxPangoFonts.cpp

@@ -1983,6 +1983,15 @@ nsString
 gfxPangoFontGroup::GetFamilyNameAt(int32_t i)
 {
     gfxFcFont* font = static_cast<gfxFcFont*>(GetFontAt(i));
+
+    if (font->GetFontEntry()->IsUserFont()) {
+        gfxFontFamily* family =
+            GetUserFontSet()->FindFamilyFor(font->GetFontEntry());
+        if (family) { // should never fail, but just in case...
+            return family->Name();
+        }
+    }
+
     return font->GetFamilyName();
 }
 

gfx/thebes/gfxUserFontSet.cpp

@@ -791,6 +791,33 @@ gfxUserFontSet::GetFamily(const nsAString& aFamilyName) const
     return mFontFamilies.GetWeak(key);
 }
 
+struct FindFamilyCallbackData {
+    gfxFontEntry  *mFontEntry;
+    gfxFontFamily *mFamily;
+};
+
+static PLDHashOperator
+FindFamilyCallback(const nsAString&    aName,
+                   gfxMixedFontFamily* aFamily,
+                   void*               aUserArg)
+{
+    FindFamilyCallbackData *d = static_cast<FindFamilyCallbackData*>(aUserArg);
+    if (aFamily->ContainsFace(d->mFontEntry)) {
+        d->mFamily = aFamily;
+        return PL_DHASH_STOP;
+    }
+
+    return PL_DHASH_NEXT;
+}
+
+gfxFontFamily*
+gfxUserFontSet::FindFamilyFor(gfxFontEntry* aFontEntry) const
+{
+    FindFamilyCallbackData d = { aFontEntry, nullptr };
+    mFontFamilies.EnumerateRead(FindFamilyCallback, &d);
+    return d.mFamily;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // gfxUserFontSet::UserFontCache - re-use platform font entries for user fonts
 // across pages/fontsets rather than instantiating new platform fonts.

gfx/thebes/gfxUserFontSet.h

@@ -193,6 +193,12 @@ public:
                                 bool& aNeedsBold,
                                 bool& aWaitForUserFont);
 
+    // Find a family (possibly one of several!) that owns the given entry.
+    // This may be somewhat expensive, as it enumerates all the fonts in
+    // the set. Currently used only by the Linux (gfxPangoFontGroup) backend,
+    // which does not directly track families in the font group's list.
+    gfxFontFamily *FindFamilyFor(gfxFontEntry *aFontEntry) const;
+
     // check whether the given source is allowed to be loaded
     virtual nsresult CheckFontLoad(const gfxFontFaceSrc *aFontFaceSrc,
                                    nsIPrincipal **aPrincipal) = 0;