Bug 1692498 - Let the emoji font pref override Unicode presentation style only if it's explicitly user-set. r=emk

Differential Revision: https://phabricator.services.mozilla.com/D105102

gfx/thebes/gfxTextRun.cpp

@@ -3329,12 +3329,14 @@ gfxFont* gfxFontGroup::FindFontForChar(uint32_t aCh, uint32_t aPrevCh,
   // 2. search pref fonts
   gfxFont* font = WhichPrefFontSupportsChar(aCh, aNextCh, presentation);
   if (font) {
-    if (PrefersColor(presentation)) {
-      // For emoji, always accept the font from preferences even if it isn't
-      // actually a color-emoji font, as some users may explicitly choose to
-      // set their emoji font preference to a monochrome font like Symbola.
-      // So the font.name-list.emoji preference takes precedence over the
-      // Unicode presentation style here.
+    if (PrefersColor(presentation) &&
+        Preferences::HasUserValue("font.name-list.emoji")) {
+      // For emoji, always accept the font from preferences if it's explicitly
+      // user-set, even if it isn't actually a color-emoji font, as some users
+      // may want to set their emoji font preference to a monochrome font like
+      // Symbola.
+      // So a user-provided font.name-list.emoji preference takes precedence
+      // over the Unicode presentation style here.
       RefPtr<gfxFont> autoRefDeref(candidateFont);
       *aMatchType = FontMatchType::Kind::kPrefsFallback;
       return font;

layout/reftests/text/1463020-letter-spacing-text-transform-1-ref.html

@@ -3,10 +3,6 @@
 <meta charset=utf-8>
 <style>
 span {
-  /* On Windows, we need to use the TwEmoji Mozilla font in preference to
-     Segoe UI Emoji, as the latter doesn't support the Regional-Indicator
-     flag ligatures. */
-  font-family: TwEmoji Mozilla, sans-serif;
   font-size: 36px;
   font-kerning: none;
 }

layout/reftests/text/1463020-letter-spacing-text-transform-1.html

@@ -3,10 +3,6 @@
 <meta charset=utf-8>
 <style>
 span {
-  /* On Windows, we need to use the TwEmoji Mozilla font in preference to
-     Segoe UI Emoji, as the latter doesn't support the Regional-Indicator
-     flag ligatures. */
-  font-family: TwEmoji Mozilla, sans-serif;
   font-size: 36px;
   font-kerning: none;
 }

layout/reftests/text/reftest.list

@@ -1,6 +1,6 @@
 # Font-dependent reftests may fail intermittently/transiently due to asynch fallback,
 # so we disable the async mechanism for this directory.
-defaults pref(gfx.font_rendering.fallback.async,false)
+defaults pref(gfx.font_rendering.fallback.async,false) pref(gfx.bundled-fonts.activate,1)
 
 fails-if(Android) == fallback-01.xhtml fallback-01-ref.xhtml
 == font-selection-by-lang-01.html font-selection-by-lang-01-ref.html