[ft] Suggestion/Inquiry: keeping metrics.horiAdvance for emboldened fixed-width fonts

[Raimund Steger]

Hi,

there has been a discussion on the fontconfig mailing list about 
artificially emboldened fixed-width fonts (this one: 
http://thread.gmane.org/gmane.comp.fonts.fontconfig/5372).

The issue that has been brought up -- not for the first time -- is that 
some text editors use bold face for syntax highlighting, and if said 
editors happen to use a font that has no native bold variant (Droid Sans 
Mono, Inconsolata, Lucida Console) the characters will not align between 
the lines as FreeType adds emboldening strength to the horizontal 
advance width which many toolkits use without modification (not terminal 
emulators though! as I've found, but... the rest).

I don't at all disagree with the current implementation in terms of 
aesthetics, but I suppose one could say that keeping monospace text in 
its proper grid (in the face of users who don't want to configure a lot) 
constitutes something like a higher cause...

Anyway. We found that older Infinality patches implemented a change to 
this exact advance width calculation that just disabled it if 
FT_FACE_FLAG_FIXED_WIDTH was set. Newer versions then started disabling 
it unconditionally, but I think that would be taking it a little too far.

Attached is a patch that's about what I have in mind.

Now I have little experience what weight such a change would carry in 
the FreeType world, whether the patch even addresses the right spot in 
the code, and if it's something you would consider acceptable in terms 
of looks (in particular, I haven't tested emboldened bitmap fonts), and 
... let's say rendering stability (I mean creating reproducible images 
across FreeType versions. I've spotted a discussion in the mailing list 
archive that suggests that some people are very serious about this). 
Still I thought it'd be worth a suggestion before some distributions 
started disabling the feature for monospace fonts through their 
fontconfig setup...

-Raimund




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emboldenmono.diff
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