How is highlighting done in show-paren-mode?

[David Abrahams]

This concerns the one remaining problem with the ClearType patch I'm
trying to clean up and submit.  I hope I don't seem too insistent, but
I've been trying to get a hint for about a week.

David Abrahams <address@hidden> writes:

> David Abrahams <address@hidden> writes:
>
>> David Abrahams <address@hidden> writes:
>>
>>> I am seeing some minor artifacts that I don't know what to do about.
>>> For example, when I backspace over these parens starting from the end
>>> of the line, I end up with some small remnants of the background color
>>> emacs uses to highlight matching parens for me.  When all the close
>>> parens are gone there's a thin vertical cyan line at the right edge of
>>> each open paren.  Any clues where to attack that?
>>>
>>> ((((()))))
>>
>> Even some vague hints would be a big help here.  This is the only
>> remaining detail as far as I can tell.
>
> I have one more piece of information for anyone who can think about
> this problem for a moment: When I do `C-s x', the first instance of x
> (or whatever character) that is found gets highlighted in purple and
> looks right.  The next instance of x on that line gets highlighted in
> cyan and looks right.  The rest of the instances of x on that line get
> highlighted in cyan, and the highlighting extends one pixel too far to
> the left.  On each line thereafter, the first instance of x is
> highlighted in cyan and looks right, and the rest of the instances on
> that line are highlighted in cyan and look wrong (i.e. the
> highlighting extends one pixel too far to the left).

Can someone please give me some hint as to which entry points to
breakpoint in order to observe these calculations and/or drawing in
action?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com