Re: master 1555453694: Implement `alpha-background' on non-Cairo builds

[Jose A Ortega Ruiz]

On Tue, Feb 01 2022, Po Lu wrote:

> Jose A Ortega Ruiz <jao@gnu.org> writes:
>
>> let me add that i just tried with emacs compiled with lucid and there
>> alpha-background works well with exwm and picom
>
> That shouldn't be possible, since it's disabled on Emacs builds with Xt,
> as Xt doesn't really know what to do with a 32-bit visual.  (i.e. Xt
> will crash and lwlib will "accidentally" draw things with the alpha
> channel set to zero.)

(what is it supposed to happen with --with-x-toolkit=no then?)

>
> Please evaluate (x-display-planes) in that Emacs build and tell me what

24.

> it returns.  Or perhaps you used the old `alpha' frame parameter, which
> does work on Xt builds, but also changes the opacity of the foreground
> text?

well, i double checked frame-parameters, and it said alpha-background.
but the effect was the same as with alpha, so i guess it was possibly a
perhaps unintended fallback.

nonetheless, after your update yesterday to apply a mask to images, and
a recompilation, alpha-background stopped working at all both in lucid
and no toolkit, which i guess is what you expect, even with a compositor
like compton.  if that's so, all is well.  i am actually happy with
alpha for my use cases (alpha-background is working well in wayland
with a pgtk build, when i'm not in x11).

cheers,
jao
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