Background color for admin's m2m multi-select "selected" rows is lost in dark theme

[Giannis Terzopoulos]

I noticed today that the color that is currently used for selected m2m items is indistinguishable. It might not be as noticeable to others, I'm not sure, I have some color difficulties. Only dark theme seems to be affected.

I am attaching 2 screenshots, how it looks on 5.1 and on 5.0.9

[Natalia Bidart]

Hello Giannis, thank you for your report!

I have tried to reproduce and these are my findings:

• in Chrome, both light and dark mode have good contrast for the selected m2m, both when the m2m widget has focus and when it does not.
• in Firefox, when using the dark theme, there is good contrast for when the m2m widget has focus but there is no color difference when the focus is moved to another element.

I bisected the regressing revno to be b47bdb4cd9149ee2a39bf1cc9996a36a940bd7d9

Would you like to prepare a patch?

[Natalia Bidart]

Added Accessibility team as cc, would you have any recommendation?

[Sarah Abderemane]

Hi Natalia,
I didn't check the code yet, but this might be an issue with the CSS class :focus on the element if there is one (or missing)
or it could be the change of ::-moz-focus-inner CSS class if the property exist in the CSS stylesheet. I can check deeper if needed :)

[GitHub <noreply@…>]

In 679d578:

Fixed #35809 -- Set background color for selected rows in the admin's form select widget.

Regression in b47bdb4cd9149ee2a39bf1cc9996a36a940bd7d9.

Thank you Giannis Terzopoulos for the review, and Tom Carrick and Sarah Boyce
for the review.

[Natalia <124304+nessita@…>]

In 17fa7592:

[5.1.x] Fixed #35809 -- Set background color for selected rows in the admin's form select widget.

Regression in b47bdb4cd9149ee2a39bf1cc9996a36a940bd7d9.

Thank you Giannis Terzopoulos for the review, and Tom Carrick and Sarah Boyce
for the review.

Backport of 679d57816d716cbc7cff3b364ae265d70444ebd9 from main.