[Webkit-unassigned] [Bug 25156] New: Missing glyphs cause white box to be rendered instead of using fallback font

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=25156

           Summary: Missing glyphs cause white box to be rendered instead of
                    using fallback font
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Macintosh
               URL: http://www.reddit.com/r/pics/comments/8c1xf/also_the_wor
                    k_of_4chan_pic/c08to2v
        OS/Version: Mac OS X 10.5
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Text
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: kevin at sb.org


When a font claims to support a character but does not have a glyph for it,
Safari renders the white box glyph instead of using a fallback font.

In the associated URL, the font is Verdana and the characters in question are
combining marks. One of the characters without a glyph is U+0314 COMBINING
REVERSED COMMA ABOVE. According to UnicodeChecker, Verdanna supports this
character, but selecting it renders absolutely no glyph at all. When WebKit
encounters the missing glyph, it should behave as if the font didn't claim to
support the character at all, but instead it renders the white box.

In odd quirk of this is that, because the original character was a combining
mark, WebKit doesn't allow the user to select the white box glyphs directly but
must select the text to both sides of it in order to copy the text. Normally
this is because combining marks combine with the previous character and thus it
doesn't make sense to try and select them, but in this case they're showing up
as unselectable white boxes and it's just confusing.

Also note that if I disable the Verdana font, whatever font WebKit is using as
a replacement also exhibits the same behavior.

Screenshot of original problem:
http://quicksnapper.com/kballard/image/webkit-combining-chars-white-boxes/
Screenshot after Verdana is disabled:
http://quicksnapper.com/kballard/image/webkit-combining-chars-white-glyph-verdana-disabled/


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