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Re: Cursor drawing

From: Eli Zaretskii
Subject: Re: Cursor drawing
Date: Fri, 21 Dec 2018 22:37:31 +0200

> From: Clément Pit-Claudel <address@hidden>
> Date: Fri, 21 Dec 2018 15:27:52 -0500
> > Doesn't drawing an image of the arrow fit the bill?
> I can't answer for Elias, of course, but for the use cases I have in mind I 
> think it wouldn't work. I think Elias' idea is that you would have arrows 
> drawn over the text, pointing from one symbol in the source code to another 
> one.  The DrRacket IDE does this to highlight bound occurrences, for example; 
> I have attached a screenshot.


This kind of drawing cannot be part of the display engine, since you
want to draw over the text, and thus redisplay will overwrite portions
of your arrows.  So you need to add code after redisplay cycle
finishes, e.g. in frame_up_to_date_hook, to redraw your arrows.  I
think I already mentioned that up-thread.  Use GUI primitives there to
draw lines and other figures, as the case may be.

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