Re: "Bold" effect when anti-aliased glyphs are overwritten

[Stephen Berman <Stephen.Berman@gmx.net>]

On Tue, 27 May 2008 17:09:29 -0400 Chong Yidong <cyd@stupidchicken.com> wrote:

> Chong Yidong <cyd@stupidchicken.com> writes:
>
>> I've been noticing that glyphs near the cursor occasionally become
>> "bold" for no reason.
>>
>> The reason this happens is that when the redisplay engine calls
>> draw_glyphs to draw certain glyphs, such as the cursor glyph,
>> neighboring glyphs are redrawn if there is a left or right overhang
>> (xdisp.c:19929).
>>
>> With anti-aliasing, it doesn't work well.  Apparently, during the
>> anti-aliasing calculation, the entire existing glyph---including the
>> glyph foreground---is treated as the "background".  Thus, the
>> anti-aliased parts of the foreground character becomes more and more
>> prominent, and eventually saturates completely.
>
> I've checked in a fix into CVS.  Please let me know if it causes any
> problems.

It fixes the cases I have encountered.  Thanks!

Steve Berman