Bug 1341085 - Implement a pref that allows OpenType Variation tables to bypass the sanitizer, as it doesn't know about them. r=jrmuizel

gfx/thebes/gfxPrefs.h

@@ -383,6 +383,7 @@ private:
   DECL_GFX_PREF(Once, "gfx.direct2d.force-enabled",            Direct2DForceEnabled, bool, false);
   DECL_GFX_PREF(Live, "gfx.direct3d11.reuse-decoder-device",   Direct3D11ReuseDecoderDevice, int32_t, -1);
   DECL_GFX_PREF(Live, "gfx.direct3d11.allow-intel-mutex",      Direct3D11AllowIntelMutex, bool, true);
+  DECL_GFX_PREF(Live, "gfx.downloadable_fonts.keep_variation_tables", KeepVariationTables, bool, false);
   DECL_GFX_PREF(Live, "gfx.downloadable_fonts.otl_validation", ValidateOTLTables, bool, true);
   DECL_GFX_PREF(Live, "gfx.draw-color-bars",                   CompositorDrawColorBars, bool, false);
   DECL_GFX_PREF(Once, "gfx.e10s.hide-plugins-for-scroll",      HidePluginsForScroll, bool, true);

gfx/thebes/gfxUserFontSet.cpp

@@ -181,15 +181,25 @@ public:
     {
         // Whether to apply OTS validation to OpenType Layout tables
         mCheckOTLTables = gfxPrefs::ValidateOTLTables();
+        // Whether to preserve Variation tables in downloaded fonts
+        mKeepVariationTables = gfxPrefs::KeepVariationTables();
     }
 
     virtual ots::TableAction GetTableAction(uint32_t aTag) override {
         // Preserve Graphite, color glyph and SVG tables,
-        // and possibly OTL tables (depending on pref)
+        // and possibly OTL and Variation tables (depending on prefs)
         if ((!mCheckOTLTables &&
              (aTag == TRUETYPE_TAG('G', 'D', 'E', 'F') ||
               aTag == TRUETYPE_TAG('G', 'P', 'O', 'S') ||
               aTag == TRUETYPE_TAG('G', 'S', 'U', 'B'))) ||
+            (mKeepVariationTables &&
+             (aTag == TRUETYPE_TAG('a', 'v', 'a', 'r') ||
+              aTag == TRUETYPE_TAG('c', 'v', 'a', 'r') ||
+              aTag == TRUETYPE_TAG('f', 'v', 'a', 'r') ||
+              aTag == TRUETYPE_TAG('g', 'v', 'a', 'r') ||
+              aTag == TRUETYPE_TAG('H', 'V', 'A', 'R') ||
+              aTag == TRUETYPE_TAG('M', 'V', 'A', 'R') ||
+              aTag == TRUETYPE_TAG('V', 'V', 'A', 'R'))) ||
             aTag == TRUETYPE_TAG('S', 'i', 'l', 'f') ||
             aTag == TRUETYPE_TAG('S', 'i', 'l', 'l') ||
             aTag == TRUETYPE_TAG('G', 'l', 'o', 'c') ||
@@ -229,6 +239,7 @@ private:
     gfxUserFontEntry* mUserFontEntry;
     nsTHashtable<nsCStringHashKey> mWarningsIssued;
     bool mCheckOTLTables;
+    bool mKeepVariationTables;
 };
 
 // Call the OTS library to sanitize an sfnt before attempting to use it.

modules/libpref/init/all.js

@@ -748,6 +748,9 @@ pref("gfx.downloadable_fonts.otl_validation", false);
 pref("gfx.downloadable_fonts.otl_validation", true);
 #endif
 
+// Whether to preserve OpenType variation tables in fonts (bypassing OTS)
+pref("gfx.downloadable_fonts.keep_variation_tables", false);
+
 #ifdef ANDROID
 pref("gfx.bundled_fonts.enabled", true);
 pref("gfx.bundled_fonts.force-enabled", false);