clamp ratio instead of resetting when overstepping

[antoineCharpentier-19]

Related Issue : #1401

This is in order to avoid sudden layout shifts when trying to push unimportant windows out of the way.
If trying to resize a window below 10% or above 90%, the ratio will clamp instead of going back to 50%.

Maybe there is a reason to want the reset to 50%, in which case this would need to be optional, I just could not think of one.

Before :

Sans.titre.09.02.56.mov

After :

Sans.titre.mov

[antoineCharpentier-19]

Apparently this code is also used in the insertion of new windows. When inserting a window or when activating a tiled layout, the ratio is initially set to 0, then corrected here. Thus, clamping blindly negated the default split ratio and always ended up with 0.1.

I do not know if there is any check to differentiate an insertion from a resizing at this point in the code, so I added a check for 0.

The behaviour is then to still reset to the default split ratio if squishing a window completely, which is easily avoidable. For every other case, it clamps to 0.1 / 0.9.

Please disregard the messy PR history..

[koekeishiya]

Fixed in a different way; see linked issue for the commit.