bug#69782: [PATCH] Fringe bitmaps should respect alpha-background

[Po Lu]

Nate Sandy <nsan@posteo.de> writes:

> Hi,
>
> fringe bitmaps currently don't respect the frame parameter
> 'alpha-background', i.e., their background is opaque. But since the
> fringe itself *does* respect 'alpha-background', fringe bitmaps should
> do the same. This patch fixes that. See attached screenshots for the
> effect.
> The alpha-background used here was set with:
>   (set-frame-parameter nil 'alpha-background 50)
>   
> I am not sure which other platforms support 'alpha-background', and
> unfortunately I am not able to test with those.

PGTK and GTK 3 or no-toolkit X builds, with either Cairo or XRender.

>
> The change is altering the parameter 'respect_alpha_background' in
> {pgtk,x}_cr_draw_image - while this name sounds quite generic, I didn't
> find any other usages of this function than drawing fringe bitmaps. I
> hope I didn't miss any.

What about x_draw_image_foreground?

> I hope that I'm following the conventions here correctly - please let me
> know if I can improve anything!

This patch is missing a ChangeLog entry.  Though your other patch fails
in several more significant respects, that can wait until the
methodological concerns are resolved.

Thanks for your interest in Emacs.