Mouse & Touchpad panel can't shrink to less than the width of scroll-test.svg
This was found in Pop!_OS when testing something related: https://github.com/pop-os/gnome-control-center/pull/103. Perhaps #910 (closed) is related here too.
Reproduction
Open the Mouse & Touchpad panel and try to shrink the window horizontally as much as you can. It won't shrink as much as other panels, leaving padding on the left and right.
Cause
After some testing, it turns out this is due to the scroll-test.svg image used in cc-mouse-test.ui (even though that's initially hidden). The window won't scale below this width when Mouse & Touchpad is open.
Solution
I guess the image should scale with window size? I don't know if there's a simple way to do that with GtkImage
. I guess it would also depend how well the image works at different sizes and screen ratios.