Touchpad & touchscreen gestures
I think we could use a plan on where we want to go with touchpad and touchscreen gestures.
The status quo
We have non-configurable touchpad 4 fingers up for the desktop effect, 4 fingers down for present windows, 4 finger left/right for switching between virtual desktops. Except for the desktop effect none are real-time. There is also the screen edge touchscreen gestures and are configurable, also not real time though and sort of unreliable at the moment (at least on my laptop).
3 finger gestures
I implemented some for window management (maximize, quick tile left/right, minimize) in work/more-touchpad-gestures and they do remove the need for some annoying mouse movements with my workflow. I think something like that could be useful and well received, especially if paired with some nice (ideally real-time) animations instead of the current blinking of the quick tile shortcuts.
I think that for the best and most intuitive experience touch(pad)gestures need to be contextual: Swipe up triggers desktop overview, so swipe down should disable it again. Same principle for present windows, quick tile and probably maximize, too. 4 finger left/right to switch between VDs should ideally work in the new overview effect. Also in the overview effect, cycling through the selected windows by scrolling / swiping with two fingers in the direction of the to-be-selected window would likely make sense.
With Qt6 we'll be able to use touchpad gestures in applications, we need to figure out how to prevent clashes - keeping apps to 3 finger and KWin to 4 is not enough, as other DEs can and do use different global shortcuts, and obviously there's also third party apps. This goes out of the scope of KWin but there's also questions on where to use them for what, and how make them commonly configurable, too. Things like "back/forward" should probably be universal.
Global touchscreen gestures
For things like screenshots, triggering present windows, quick tiling etc. What should be 3, what should be 4 fingers? Should 3 fingers maybe be reserved for moving windows like you can with Meta+LeftClick on laptops instead of normal gestures?
How far should it go? Do we want to have (at least a subset of) normal shortcuts that can generally be set to be triggered by touch(pad) gestures, or should it stay separate, like screen edges?