GNU bug report logs - #51411
NS port cleanups

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From: Po Lu <luangruo <at> yahoo.com>
To: Alan Third <alan <at> idiocy.org>
Cc: 51411 <at> debbugs.gnu.org
Subject: bug#51411: NS port cleanups
Date: Thu, 28 Oct 2021 09:09:33 +0800

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Alan Third <alan <at> idiocy.org> writes:

> That function is a real mess of calls to ns_focus and ns_unfocus. I
> think there's no good reason for them to be called as often as they
> are, and some related functions (ns_dumpglyphs_stretch) don't need to
> call them themselves either.

> I think we need to have a rethink of how clipping is handled here. We
> don't need to use ns_focus to clip and we repeatedly call ns_focus on
> the same rectangle. For a lot of those calls we could replace them
> with a single clipping rectangle and adjust it as required for
> overhangs or whatever.

> I also think you misunderstood what I was saying about the performance
> problems with calling saveGraphicsState. Calling it when not required
> is frowned upon by Apple as they say it causes performance problems.
> Your code is now calling it in ns_focus whether it's required or not.
> Ideally we only call it when modifying the clipping rectangle, because
> there are times ns_focus is called where we don't modify the clipping
> rectangle and therefore we don't need to save the graphics context.

I understand what you mean now, thanks.

> I understand what you did, but I think the better solution is for us
> is to try to untangle ns_draw_glyph_string, even if that means saving
> the context there directly on occasion.

> If you want me to have a look at it let me know, I think I know what
> needs to be done, but I probably won't get round to it as soon as you
> could.

Thanks.  I had a try at it, cleaning up much of what appeared obviously
unnecessary.  (Though I did not dare change what seemed to be mysterious
to me.)

Though, OTOH, I think calling saveGraphicsState inside the overhang draw
process is not too much of a problem as it happens infrequently enough
to not be relevant.

[0001-Improve-font-display-on-NS-port.patch (text/x-patch, attachment)]

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I think these changes are appropriate enough for the font display patch,
as they affect cursor display and overhang drawing.

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