1066933 - Unicode characters break Emoji Color

Status: RESOLVED DUPLICATE of bug 1032671

(Core :: Graphics: Text, defect)

Description

[ivs]

Attachment: report.png

User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:35.0) Gecko/20100101 Firefox/35.0
Build ID: 20140910030204

Steps to reproduce:

Firefox 35.0a1(and possible some previous version?) have support for colored emoji unicode character. Under most circumstances it works properly, I have discovered a way to break it.

Create a string of "emoji" unicode characters:

Comment 1

[Alice0775 White]

See detail http://forums.mozillazine.org/viewtopic.php?f=23&t=2868485

Comment 2

[Gingerbread Man]

Attachment: emoji_color.html

Looks like a font fallback problem [1]. The fontinfo add-on [2] reveals the font in use is Segoe UI Symbol, rather than Segoe UI Emoji.

See the attached testcase:
1. There's no issue if Segoe UI Emoji is expressly specified. Setting "Fonts for: Other Languages" to "Proportional: Sans Serif; Sans-serif: Segoe UI Emoji" also solves the problem.
2. This only affects certain emoji. Presumably that's because the others aren't available in the Segoe UI Symbol font, so Firefox picks Segoe UI Emoji.

[1] See bug 1054780 since it has the potential to make this worse.
[2] https://addons.mozilla.org/firefox/addon/fontinfo/

Comment 3

[Jonathan Kew [:jfkthame]]

The emoji characters generally rely on system font fallback, as we don't currently have an explicit font preference for them.

I assume what's happening here is that we hit this code in gfxFontGroup::FindFontForChar:

6026     // 3. use fallback fonts
6027     // -- before searching for something else check the font used for the previous character
6028     if (aPrevMatchedFont && aPrevMatchedFont->HasCharacter(aCh)) {
6029         *aMatchType = gfxTextRange::kSystemFallback;
6030         nsRefPtr<gfxFont> ret = aPrevMatchedFont;
6031         return ret.forget();
6032     }

which means that if the immediately-preceding character came from Segoe UI Symbol, and the emoji codepoints in question are also available in Segoe UI Symbol, then we'll continue using that rather than falling back to Segoe UI Emoji, as we otherwise would for the emoji codepoints in isolation.

Comment 4

[Makoto Kato [:m_kato]]

This will be fixed by bug 1032671.