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Re: Some fonts rendered incorrectly since upgrade to Qt 5.9.1

On Sonntag, 3. September 2017 23:44:30 CEST Miguel A. Vallejo wrote:
> > It was also be good to know if the issue goes away if you enable
> > antialiasing.
> Yes, enabling antialiasing solves the problem. It is just bold text,
> rendered fine. But I must turn antialising off. Fuzzy and blurry fonts
> produce me headache and visual fatigue.

If you have full hinting enabled and well hinted fonts, it shouldn't be 
blurry,but note modern fonts are typically terribly hinted because they are 
made more for high res screens or for macs where blurry text is considered 
part of the key asthethics. For an example of well-hinted fonts I personally 
recommend the liberation fonts, but only v1, the 2.0 update broke the world 
class hinting the fonts had, which is why debian has both. Good hinting 
usually also the only way outline fonts are rendered half decent with 
antialiasing off.

Back to the bug. I made a change in Qt's freetype font engine in 5.9 which is 
that for OpenType fonts stem darkening was enabled to make antialiasing work 
better with gamma-corrected blending. Since this is for a special type of 
antialiasing, it shouldn't happen when antialiasing is disabled, but it is one 
possibility of something that could have gone wrong and gotten activated when 
it shouldn't.

But another thing that could have gone wrong is that freetype is starting to 
prioritize non-antialiasing rendering or higher levels of hinting less and 
less, so newer versions of freetype can often makes such rendering worse. 
Which is why I asked if you had upgraded that recently.


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