plugins/overview: adjust swipe snapping threshold
At the current setting a swipe is required to progress to at least 50% of the full animation before snapping into overview mode (or away from it).
In my testing, this seems to be too high to reliably activate on quick and short gestures, so I have to swing my palm annoyingly far in order to reliably trigger it, which doesn't seem to be needed for switching virtual desktops (3 finger left/right swipe).
I did some blaming, it looks like the 50% setting was introduced when first adding touchpad support in this commit by @mart, possibly by just copying this value from the screen edge gestures.
The similar setting for switching virtual desktops is set to 25%. And it look like both the desktop switching and the overview animations are taking the same 2.5cm to fully complete on my touchpad.
This MR reduces the threshold for the vertical swipe used in overview to 10% of the full animation. A smaller value than for the horizontal swipe, since touchpads are typically shorter vertically than horizontally and a prolonged vertical gesture is harder to execute.
The only downside after this change I notice is that canceling the overview transition (without completing the animation) requires a bit more precision. Although this's probably not how you typically use this gesture. And this change also makes reliably deactivating overview by swiping backwards easier.
Closes: !9479 (closed)