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Re: Cursor drawing

From: Stefan Monnier
Subject: Re: Cursor drawing
Date: Thu, 20 Dec 2018 14:18:22 -0500
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

> into pixels" part: I suspect that you have some mental model of that
> which is not entirely consistent with what the code actually does.

I'd be surprised if my mental model is actually consistent with what
happens, yes ;-)

> So maybe you should say more about how you imagine this works, and how
> under that mental model you envision this part:
>> - redraw of a clipping region is done by "rendering" the corresponding
>>   part of a glyph matrix combined with the corresponding part of the
>>   overlay layer into pixels.

I imagine this as being done possibly as;

1- draw the relevant glyphs from the glyph matrix
2- draw the relevant part of the overlay on top of it (with some form of
   transparency so as not to completely overwrite what was drawn in step 1).

> The crucial part here, for me, is how this "combination" would be
> different from "shoehorning crosshairs into the glyph matrix".  Can
> you elaborate on what you had in mind?

The crosshairs don't need to be represented/mentioned in the glyph matrix.

You can just keep in the overlay layer an entry that says "draw vertical
line at pixel column X" and "draw horizontal line at pixel line Y".

>> The advantage would be mostly that the overlay data structure could be
>> designed completely differently from glyph-matrices
> Like what, for example?

Maybe more like an SVG canvas?


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