Subject: bug#71850: macOS (Cocoa) alpha-background

From: Jon Rubens <[email-masked]>
Date: Wed, 19 Feb 2025 16:39:15 -0800

> > The patch seeks to enable the alpha_background frame parameter for
> > MacOS (and NS). Presently, that frame parameter does nothing on MacOS.
> > Similar to the alpha frame parameter, this should enable transparency
> > but not change the transparency of any text.

> Could you please send some instructions for how to test the patch?
> I'm looking for an easy-to-use recipe that would demonstrate the effect
> before and after applying this patch.

To test, run emacs with eval:
emacs -Q --eval="(modify-all-frames-parameters '((alpha-background . 0.5)))"
compare with changing "alpha" instead:
emacs -Q --eval="(modify-all-frames-parameters '((alpha . 0.5)))"
Notice that the text does not become transparent when alpha-background is used.
Test with themes. Larger font size makes the effect more obvious.

> Also, is there anything else you could add regarding the use case here?
Emacs already has the alpha-background frame parameter. This patch
enables the feature for MacOS to match X.

-- 
Jon