GNU bug report logs - #71850
[PATCH] macOS (Cocoa) alpha-background

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From: Jon Rubens <jonathan.rubens <at> gmail.com>
To: Stefan Kangas <stefankangas <at> gmail.com>
Cc: rudolf <at> adamkovic.org, alan <at> idiocy.org, 71850 <at> debbugs.gnu.org, alexander.adolf <at> condition-alpha.com
Subject: bug#71850: macOS (Cocoa) alpha-background
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

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