At this point, I am not sure if it is an Ubuntu specific bug. The current conditions I know of to trigger the bug are:
- Firefox 1.5 (I am using the 1.5.dfsg+18.104.22.168-1ubuntu10 package).
- Pango rendering enabled (the default for Ubuntu).
- The web page must use a font that contains ligatures and use those ligatures. Since the “DejaVu Sans” includes ligatures and is the default “sans serif” font in Dapper, this is true for a lot of websites.
- The text must be justified (e.g. use the “text-align: justify” CSS rule).
If you view a site where these conditions are met with an affected Firefox build, you will see the bug: ligature glyphs will be used to render character sequences like “ffi“, but only the advance of the first character’s normal glyph is used before drawing the next glyph. This results in overlapping glyphs
It also results in a weird effect when selecting text, since the ligatures get broken appart if the selection begins or ends in the middle of the ligature, causing the text to jump around.
I wonder if this bug affects the Firefox packages in any other distributions, or is an Ubuntu only problem?