SUMMARY Currently if you disable the touchpad on a laptop and click apply, you are left with no pointer control and have to suddenly improvise and quickly learn to use the keyboard navigation to re-enable it, which is not very straightforward (I just tried it out with no prior experience and it was pretty challenging). Adding a "keep/revert" timer popup, like when changing display settings, could be a nice user safety feature. This could also help if you set your pointer speed way too high (or low) and consequently have difficulty hitting the buttons and moving the sliders to lower it back down. The touchpad settings have a spinbox to control the pointer speed in addition to the slider bar, but the mouse settings seem to lack one. The spinbox is helpful because, rather than slamming the bar to its edges with a speedy pointer, you can spend a few minutes positioning your mouse just right and then just click repeatedly until the speed is lowered back down (or type it in), then spend a few more minutes positioning your mouse over the Apply button. OS: openSUSE Tumbleweed, latest snapshot
Probably we should disable the ability to disable the active pointing device when it's the only one (i.e. no other mouse or touchpad connected). The speed issue is more easily fixable on your own and I don't think we need to do anything there.
Makes sense to me. Maybe also count touchscreen since it can practically replace a mouse/touchpad too? The only counterpoint I can think of is users who want to go keyboard-only and disable a laptop's touchpad, but I'd assume that's pretty niche. Newer or less-savvy users are probably a better demographic to have in mind for this, I'd say.
I think our recent trend of showing a warning inline message if you uncheck "Device enabled" on all devices could be an easy good fit here. (I'm not sure how to cross-check between all the different input device kcms for which are enabled though)