Bug 1418818 - Allow downloadable fonts to include CBLC/CBDT tables on platforms where we're using Freetype. r=jrmuizel

gfx/thebes/gfxPrefs.h

@@ -460,6 +460,7 @@ private:
   DECL_GFX_PREF(Once, "gfx.direct3d11.enable-debug-layer",     Direct3D11EnableDebugLayer, bool, false);
   DECL_GFX_PREF(Once, "gfx.direct3d11.break-on-error",         Direct3D11BreakOnError, bool, false);
   DECL_GFX_PREF(Once, "gfx.direct3d11.sleep-on-create-device", Direct3D11SleepOnCreateDevice, int32_t, 0);
+  DECL_GFX_PREF(Live, "gfx.downloadable_fonts.keep_color_bitmaps", KeepColorBitmaps, bool, false);
   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);

gfx/thebes/gfxUserFontSet.cpp

@@ -180,6 +180,8 @@ public:
         mCheckOTLTables = gfxPrefs::ValidateOTLTables();
         // Whether to preserve Variation tables in downloaded fonts
         mKeepVariationTables = gfxPrefs::KeepVariationTables();
+        // Whether to preserve color bitmap glyphs
+        mKeepColorBitmaps = gfxPrefs::KeepColorBitmaps();
     }
 
     virtual ots::TableAction GetTableAction(uint32_t aTag) override {
@@ -199,7 +201,11 @@ public:
               aTag == TRUETYPE_TAG('V', 'V', 'A', 'R'))) ||
             aTag == TRUETYPE_TAG('S', 'V', 'G', ' ') ||
             aTag == TRUETYPE_TAG('C', 'O', 'L', 'R') ||
-            aTag == TRUETYPE_TAG('C', 'P', 'A', 'L')) {
+            aTag == TRUETYPE_TAG('C', 'P', 'A', 'L') ||
+            (mKeepColorBitmaps &&
+             (aTag == TRUETYPE_TAG('C', 'B', 'D', 'T') ||
+              aTag == TRUETYPE_TAG('C', 'B', 'L', 'C'))) ||
+            false) {
             return ots::TABLE_ACTION_PASSTHRU;
         }
         return ots::TABLE_ACTION_DEFAULT;
@@ -232,6 +238,7 @@ private:
     nsTHashtable<nsCStringHashKey> mWarningsIssued;
     bool mCheckOTLTables;
     bool mKeepVariationTables;
+    bool mKeepColorBitmaps;
 };
 
 // Call the OTS library to sanitize an sfnt before attempting to use it.

modules/libpref/init/all.js

@@ -791,6 +791,11 @@ pref("gfx.downloadable_fonts.otl_validation", false);
 pref("gfx.downloadable_fonts.otl_validation", true);
 #endif
 
+// Whether to preserve color bitmap tables in fonts (bypassing OTS).
+// Currently these are supported only on platforms where we use Freetype
+// to render fonts (Linux/Gtk and Android).
+pref("gfx.downloadable_fonts.keep_color_bitmaps", false);
+
 // Whether to preserve OpenType variation tables in fonts (bypassing OTS)
 pref("gfx.downloadable_fonts.keep_variation_tables", false);