[squeak-dev] Re: [Ann] Enhanced StrikeFonts (antiAliasing, subPixel AA)

Andreas Raab andreas.raab at gmx.de
Wed Aug 5 02:46:10 UTC 2009


Juan Vuletich wrote:
> You're right. It seems we need the second BitBlt pass even for black 
> text. Just added that to the trunk. I also added a preference, 
> #properAlphaForBlackText that defaults to true, but can be set to false 
> if performance is more important that correctness.

Yeah, good choice. It turns out that there is a measurable performance 
difference between single-pass and two-pass rendering (for example in 
the browser benchmark). Is it possible to merge these specific two rules 
into a single-pass rendering to retain the original single-pass performance?

> Note #1. This needs a rather recent VM, that includes my fixes to BitBlt 
> done in April. Your latest Windows VM is ok.
> 
> Note #2. If the trend is to fix the handling of alpha channel in the 
> image, at some point the fix to ignore Display alpha must be removed 
> from the Linux VM, to play well with composing window managers.

Yes, we should. It would be nice if we could actually control the alpha 
correctly.

> Note #3. The second pass stuff is done in GrafPort, but not in BitBlt. 
> Do you think it is better to move it up to BitBlt?

BitBlt, since it's used directly from StrikeFont and not via Canvas.

Cheers,
   - Andreas



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