Re: Emacs canvas support

[Stefan Monnier <monnier@iro.umontreal.ca>]

> This is sounding more and more like a compositor :-)

Yes, the combination of the glyph matrix and the canvas is done by
"a compositor", indeed.  But it's a kind of "trivial" version of
a compositor, and it's a very small part of the work (the work taking
place mostly on the canvas side where we'll need to draw at positions
that depend on the glyph matrix).

> Nit: perhaps we'd like to have pics below as well as above text.

Not sure if the benefit is worth adding complexity for that.
But maybe it's easy and natural to make the layering between glyph
matrix and canvas into an arbitrary stack of layers.

E.g. I could imagine a design where windows can display a stack of
buffers layered one on top of the other (where typically only one of
them contains text and the rest only contains canvas objects).
But "synchronizing" the canvas in one buffer with the text in the other
buffer would likely be more difficult than if we add a canvas "overlay"
directly to the buffers.


        Stefan