b=597147 part 19: simplify gfxFcFont/gfxPangoFcFont ownership a little r=jfkthame

--HG--
extra : rebase_source : c7288edd9faefde36543d635c37b8a05d3d18a7b

gfx/thebes/gfxPangoFonts.cpp

@@ -600,23 +600,16 @@ struct gfxPangoFcFont {
     PangoCoverage *mCoverage;
     gfxFcFont *mGfxFont;
 
-    // The gfxPangoFcFont adds a reference to |aGfxFont| and |aFontPattern|.
+    // The caller promises to ensure that |aGfxFont| remains valid until the
+    // new gfxPangoFcFont is destroyed.  See PangoFontToggleNotify.
+    //
+    // The gfxPangoFcFont holds a reference to |aFontPattern|.
     // Providing one of fontconfig's font patterns uses much less memory than
     // using a fully resolved pattern, because fontconfig's font patterns are
     // shared and will exist anyway.
-    //
-    // Note that the ownership between this PangoFont and the gfxFcFont is
-    // shared and the gfxFcFont will sometimes remove its reference added
-    // here.  See PangoFontToggleNotify.
     static nsReturnRef<PangoFont>
     NewFont(gfxFcFont *aGfxFont, FcPattern *aFontPattern);
 
-    // Tell |this| that it no longer needs the gfxFcFont and the caller
-    // assumes ownership of the gfxFcFont reference added at construction of
-    // |this|.  The method is called just before the gfxFcFont removes the
-    // last reference to |this|.
-    void ForgetGfxFont() { mGfxFont = nsnull; }
-
     gfxFcFont *GfxFont() { return mGfxFont; }
 
     cairo_scaled_font_t *CairoFont()
@@ -641,7 +634,6 @@ gfxPangoFcFont::NewFont(gfxFcFont *aGfxFont, FcPattern *aFontPattern)
     gfxPangoFcFont *font = static_cast<gfxPangoFcFont*>
         (g_object_new(GFX_TYPE_PANGO_FC_FONT, "pattern", aFontPattern, NULL));
 
-    NS_ADDREF(aGfxFont);
     font->mGfxFont = aGfxFont;
     font->SetFontMap();
 
@@ -704,7 +696,6 @@ gfx_pango_fc_font_finalize(GObject *object)
 
     if (self->mCoverage)
         pango_coverage_unref(self->mCoverage);
-    NS_IF_RELEASE(self->mGfxFont);
 
     G_OBJECT_CLASS(gfx_pango_fc_font_parent_class)->finalize(object);
 }
@@ -1886,7 +1877,7 @@ gfxFcFont::gfxFcFont(cairo_scaled_font_t *aCairoFont,
 }
 
 // The gfxFcFont keeps (only) a toggle_ref on mPangoFont.
-// While mPangoFont has other references, a reference (from mPangoFont) to the
+// While mPangoFont has other references, a reference to the
 // gfxFcFont is held.  While mPangoFont has no other references, the reference
 // to the gfxFcFont is removed.
 static void
@@ -1907,13 +1898,15 @@ gfxFcFont::MakePangoFont()
     nsAutoRef<PangoFont> pangoFont(gfxPangoFcFont::NewFont(this, mFontPattern));
     mPangoFont = pangoFont;
     g_object_add_toggle_ref(G_OBJECT(mPangoFont), PangoFontToggleNotify, this);
+    // This self-reference gets removed when the normal reference to the
+    // PangoFont is removed as the nsAutoRef goes out of scope.
+    NS_ADDREF(this);
 }
 
 gfxFcFont::~gfxFcFont()
 {
     cairo_scaled_font_set_user_data(mScaledFont, &sGfxFontKey, NULL, NULL);
     if (mPangoFont) {
-        GFX_PANGO_FC_FONT(mPangoFont)->ForgetGfxFont();
         g_object_remove_toggle_ref(G_OBJECT(mPangoFont),
                                    PangoFontToggleNotify, this);
     }