Use font.name-list.emoji preference for emoji presenration.

gfx/thebes/gfxFontConstants.h

@@ -222,13 +222,14 @@ enum {
 #define NS_FONT_SUB_SUPER_SMALL_SIZE             (20.0)
 #define NS_FONT_SUB_SUPER_LARGE_SIZE             (45.0)
 
-// pref lang id's for font prefs
+// pref lang ids for font prefs
 enum eFontPrefLang {
     #define FONT_PREF_LANG(enum_id_, str_, atom_id_) eFontPrefLang_ ## enum_id_
     #include "gfxFontPrefLangList.h"
     #undef FONT_PREF_LANG
 
     , eFontPrefLang_CJKSet  // special code for CJK set
+    , eFontPrefLang_Emoji   // special code for emoji presentation
     , eFontPrefLang_First = eFontPrefLang_Western
     , eFontPrefLang_Last = eFontPrefLang_Others
     , eFontPrefLang_Count = (eFontPrefLang_Last - eFontPrefLang_First + 1)

gfx/thebes/gfxFontFamilyList.h

@@ -38,6 +38,7 @@ enum FontFamilyType : uint32_t {
   // special
   eFamily_moz_variable,
   eFamily_moz_fixed,
+  eFamily_moz_emoji,
 
   eFamily_generic_first = eFamily_serif,
   eFamily_generic_last = eFamily_fantasy,

gfx/thebes/gfxPlatformFontList.cpp

@@ -869,19 +869,9 @@ gfxPlatformFontList::ResolveGenericFontNames(
     nsIAtom* langGroup = GetLangGroupForPrefLang(aPrefLang);
     NS_ASSERTION(langGroup, "null lang group for pref lang");
 
-    // lookup and add platform fonts uniquely
-    for (const nsString& genericFamily : genericFamilies) {
-        gfxFontStyle style;
-        style.language = langGroup;
-        style.systemFont = false;
-        AutoTArray<gfxFontFamily*,10> families;
-        FindAndAddFamilies(genericFamily, &families, &style);
-        for (gfxFontFamily* f : families) {
-            if (!aGenericFamilies->Contains(f)) {
-                aGenericFamilies->AppendElement(f);
-            }
-        }
-    }
+    gfxPlatformFontList::GetFontFamiliesFromGenericFamilies(genericFamilies,
+                                                            langGroup,
+                                                            aGenericFamilies);
 
 #if 0  // dump out generic mappings
     printf("%s ===> ", prefFontName.get());
@@ -893,6 +883,43 @@ gfxPlatformFontList::ResolveGenericFontNames(
 #endif
 }
 
+void
+gfxPlatformFontList::ResolveEmojiFontNames(
+    nsTArray<RefPtr<gfxFontFamily>>* aGenericFamilies)
+{
+    // emoji preference has no lang name
+    AutoTArray<nsString,4> genericFamilies;
+
+    nsAutoCString prefFontListName("font.name-list.emoji");
+    gfxFontUtils::AppendPrefsFontList(prefFontListName.get(), genericFamilies);
+
+    gfxPlatformFontList::GetFontFamiliesFromGenericFamilies(genericFamilies,
+                                                            nullptr,
+                                                            aGenericFamilies);
+}
+
+void
+gfxPlatformFontList::GetFontFamiliesFromGenericFamilies(
+    nsTArray<nsString>& aGenericNameFamilies,
+    nsAtom* aLangGroup,
+    nsTArray<RefPtr<gfxFontFamily>>* aGenericFamilies)
+{
+    // lookup and add platform fonts uniquely
+    for (const nsString& genericFamily : aGenericNameFamilies) {
+        gfxFontStyle style;
+        style.language = aLangGroup;
+        style.systemFont = false;
+        AutoTArray<gfxFontFamily*,10> families;
+        FindAndAddFamilies(genericFamily, &families, FindFamiliesFlags(0),
+                           &style);
+        for (gfxFontFamily* f : families) {
+            if (!aGenericFamilies->Contains(f)) {
+                aGenericFamilies->AppendElement(f);
+            }
+        }
+    }
+}
+
 nsTArray<RefPtr<gfxFontFamily>>*
 gfxPlatformFontList::GetPrefFontsLangGroup(mozilla::FontFamilyType aGenericType,
                                            eFontPrefLang aPrefLang)
@@ -902,6 +929,17 @@ gfxPlatformFontList::GetPrefFontsLangGroup(mozilla::FontFamilyType aGenericType,
         aGenericType = eFamily_monospace;
     }
 
+    if (aGenericType == eFamily_moz_emoji) {
+        // Emoji font has no lang
+        PrefFontList* prefFonts = mEmojiPrefFont.get();
+        if (MOZ_UNLIKELY(!prefFonts)) {
+            prefFonts = new PrefFontList;
+            ResolveEmojiFontNames(prefFonts);
+            mEmojiPrefFont.reset(prefFonts);
+        }
+        return prefFonts;
+    }
+
     PrefFontList* prefFonts =
         mLangGroupPrefFonts[aPrefLang][aGenericType].get();
     if (MOZ_UNLIKELY(!prefFonts)) {
@@ -1180,6 +1218,10 @@ gfxPlatformFontList::AppendPrefLang(eFontPrefLang aPrefLangs[], uint32_t& aLen,
 mozilla::FontFamilyType
 gfxPlatformFontList::GetDefaultGeneric(eFontPrefLang aLang)
 {
+    if (aLang == eFontPrefLang_Emoji) {
+      return eFamily_moz_emoji;
+    }
+
     // initialize lang group pref font defaults (i.e. serif/sans-serif)
     if (MOZ_UNLIKELY(mDefaultGenericsLangGroup.IsEmpty())) {
         mDefaultGenericsLangGroup.AppendElements(ArrayLength(gPrefLangNames));

gfx/thebes/gfxPlatformFontList.h

@@ -380,6 +380,15 @@ protected:
                             eFontPrefLang aPrefLang,
                             nsTArray<RefPtr<gfxFontFamily>>* aGenericFamilies);
 
+    void
+    ResolveEmojiFontNames(nsTArray<RefPtr<gfxFontFamily>>* aGenericFamilies);
+
+    void
+    GetFontFamiliesFromGenericFamilies(
+        nsTArray<nsString>& aGenericFamilies,
+        nsAtom* aLangGroup,
+        nsTArray<RefPtr<gfxFontFamily>>* aFontFamilies);
+
     virtual nsresult InitFontListForPlatform() = 0;
 
     void ApplyWhitelist();
@@ -436,6 +445,8 @@ protected:
                          eFontPrefLang_First,
                          eFontPrefLang_Count> mLangGroupPrefFonts;
 
+    mozilla::UniquePtr<PrefFontList> mEmojiPrefFont;
+    
     // when system-wide font lookup fails for a character, cache it to skip future searches
     gfxSparseBitSet mCodepointsWithNoFonts;
 

gfx/thebes/gfxTextRun.cpp

@@ -45,6 +45,9 @@ using mozilla::services::GetObserverService;
 static const char16_t kEllipsisChar[] = { 0x2026, 0x0 };
 static const char16_t kASCIIPeriodsChar[] = { '.', '.', '.', 0x0 };
 
+const uint32_t kVariationSelector15 = 0xFE0E; // text presentation
+const uint32_t kVariationSelector16 = 0xFE0F; // emoji presentation
+
 #ifdef DEBUG_roc
 #define DEBUG_TEXT_RUN_STORAGE_METRICS
 #endif
@@ -2813,7 +2816,7 @@ gfxFontGroup::FindFontForChar(uint32_t aCh, uint32_t aPrevCh, uint32_t aNextCh,
         return nullptr;
 
     // 2. search pref fonts
-    RefPtr<gfxFont> font = WhichPrefFontSupportsChar(aCh);
+    RefPtr<gfxFont> font = WhichPrefFontSupportsChar(aCh, aNextCh);
     if (font) {
         *aMatchType = gfxTextRange::kPrefsFallback;
         return font.forget();
@@ -3081,15 +3084,25 @@ gfxFontGroup::ContainsUserFont(const gfxUserFontEntry* aUserFont)
 }
 
 already_AddRefed<gfxFont>
-gfxFontGroup::WhichPrefFontSupportsChar(uint32_t aCh)
+gfxFontGroup::WhichPrefFontSupportsChar(uint32_t aCh, uint32_t aNextCh)
 {
     RefPtr<gfxFont> font;
 
-    // get the pref font list if it hasn't been set up already
-    uint32_t unicodeRange = FindCharUnicodeRange(aCh);
+    eFontPrefLang charLang;
     gfxPlatformFontList* pfl = gfxPlatformFontList::PlatformFontList();
-    eFontPrefLang charLang = pfl->GetFontPrefLangFor(unicodeRange);
 
+    EmojiPresentation emoji = GetEmojiPresentation(aCh);
+    if ((emoji != EmojiPresentation::TextOnly &&
+         (aNextCh == kVariationSelector16 ||
+          (emoji == EmojiPresentation::EmojiDefault &&
+           aNextCh != kVariationSelector15)))) {
+        charLang = eFontPrefLang_Emoji;
+    } else {
+        // get the pref font list if it hasn't been set up already
+        uint32_t unicodeRange = FindCharUnicodeRange(aCh);
+        charLang = pfl->GetFontPrefLangFor(unicodeRange);
+    }
+ 
     // if the last pref font was the first family in the pref list, no need to recheck through a list of families
     if (mLastPrefFont && charLang == mLastPrefLang &&
         mLastPrefFirstFont && mLastPrefFont->HasCharacter(aCh)) {

gfx/thebes/gfxTextRun.h

@@ -917,7 +917,8 @@ public:
 
 protected:
     // search through pref fonts for a character, return nullptr if no matching pref font
-    already_AddRefed<gfxFont> WhichPrefFontSupportsChar(uint32_t aCh);
+    already_AddRefed<gfxFont> WhichPrefFontSupportsChar(uint32_t aCh,
+                                                        uint32_t aNextCh);
 
     already_AddRefed<gfxFont>
         WhichSystemFontSupportsChar(uint32_t aCh, uint32_t aNextCh,