| Summary: | Non-ideal rendering of Latin ligatures for 'fl' and 'fi' | ||
|---|---|---|---|
| Product: | freetype | Reporter: | F Wolff <friedel> |
| Component: | general | Assignee: | Werner Lemberg <wl> |
| Status: | RESOLVED FIXED | QA Contact: | |
| Severity: | normal | ||
| Priority: | medium | CC: | freedesktop, me |
| Version: | unspecified | ||
| Hardware: | Other | ||
| OS: | Linux (All) | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
| Attachments: | Rendering with pango | ||
That's a FreeType bug, and unfortunately we can't do anything to fix that in our font. The problem happens with the freetype autohinter, so try to enable the bytecode interpreter for font hinting (so it uses the hinting as defined by the font). *** Bug 18899 has been marked as a duplicate of this bug. *** (In reply to comment #1) > That's a FreeType bug, and unfortunately we can't do anything to fix that in > our font. The problem happens with the freetype autohinter, so try to enable > the bytecode interpreter for font hinting (so it uses the hinting as defined by > the font). > It is NOT a FreeType Bug, as per upstream FreeType developers. I have reported this bug upstream to FreeType and they insist that this is not their bug, either. Re-opening so we can pursue this further. It's very noticeable on Fedora 10, too. I'd like to hear their arguments then why it's a bug in DejaVu. The reasons why it's not are quite clear: * we have truetype hinting that force the ligatures to have the exact height as the normal letters "f" and "i". These have been verified numerous times in the past. * The outlines of the fi ligatures are also exactly the same compared to "f" and "i". * Fedora disables the freetype bytecode interpreter (which is needed to read those truetype hinting instructions) (patent reasons), and makes use of the freetype autohinter that doesn't read the hinting instructions * Without the instructions, the only thing that freetype can use to render the glyphs are some smart algorithms, and the only data it can use from the font are the glyph outlines. * The outlines are correctly sized, as mentioned above. There's not a single different thing we can do in a font to influence the behaviour of the freetype autohinter in some way. * Hence, the only reason why the glyphs you see are misrendered is that something is wrong in the algorithms used by the freetype autohinter, since that's the only thing that can affect the shapes you see. Now, if Freetype autohinters have another opinion, then I'd like to hear it. For now, this is clearly not our bug. Here is FreeType's discussion on the bug: http://savannah.nongnu.org/bugs/?25013 (In reply to comment #5) > Here is FreeType's discussion on the bug: > > http://savannah.nongnu.org/bugs/?25013 > I pointed out that the bug only appears when the autohinter is enabled. That rather clearly implicates a FreeType problem, since I'm not changing around Fontconfig or Pango. Well, the report you mention has nothing to do with this rendering bug... You asked for a way to disable the ligatures, and didn't mention anything about freetype rendering them incorrectly with their autohinter... Sorry, this is the correct link: http://savannah.nongnu.org/bugs/?21190 (In reply to comment #7) > Well, the report you mention has nothing to do with this rendering bug... You > asked for a way to disable the ligatures, and didn't mention anything about > freetype rendering them incorrectly with their autohinter... > Incidentally the original report does mention that. This should be fixed now with the current CVS. It was indeed a bug in FreeType but on the configuration side (the CJK hinter was applied to the Latin ligature block in Unicode). Please test. I have confirmed the bug is fixed in the latest FreeType CVS for the offending Latin ligatures in the DejaVu font family. Thank you for your effort! |
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Created attachment 16482 [details] Rendering with pango Using Dejavu 2.23 as packaged for Mandriva 2008.1, I get the following rendering of the Latin ligatures ff and fi, in which the ligatures do not correspond well to the normal rendering of the letter 'f'. The attachment is generated with: pango-view "--font=DejaVu Sans" --output=dejavu-2.23_ligatures.png ligature Notice how the bar of the 'f' is not on the same height, the hinting at the bottom does not correspond, and the height of the glyphs don't correspond. Perhaps extra information from my system might be useful - not sure what though, so feel free to say if important information is missing, or this is a known problem.