Re: Cairo branch.

[Jan D.]

Stefan Monnier skrev den 2015-02-11 22:49:
> > I have pushed a cairo branch.
>
> Can you give a short summary of what it brings (and/or what it could
> bring)?


YAMAMOTO Mitsuharu made the patch to demonstrate printing, so that is 
new (see x-print-frames-dialog or the Printing section in xfns.c).

Otherwise it is just a step to keep up with the times, i.e. server side 
(as in X11 server) rendering is going away as it seems.  So Emacs must 
at some point develop client side (cairo) rendering.

It could form a basis for porting to other window systems like Wayland, 
that has no rendering of its own, but relies on cairo.  That takes more 
effort, the cairo branch is X only.  Note that porting to Wayland isn't 
as simple as switching rendering, the whole event handling must be 
implemented.

As for user visible changes, there is nothing, except printing.  The 
current X rendering is still better, for speed and image support.
Image support when using cairo is lacking, PNG only.  Work needs to be 
done here (hint, hint :-).

I think using cairo and going double buffer in Emacs is easier than 
making X double buffered.  The main obstacle to double buffering is the 
way Emacs does redraw, i.e. not in the GUI loop, but outside it.  This 
is tricky to change, as there are lots of flags in the redraw code that 
gets set and reset at various points.  Figuring all that stuff out is 
not easy.

        Jan D.