Add "Increase/Decrease window height" actions

[jinliu]

The "Stacking offset Y" config is reused as the step size.

[peterfajdiga]

Thanks for the PR.

I have a problem with this approach, though. When you're changing the height of a window, you're also changing the height of another window (its upper or lower neighbor). But with this approach you have no control over which of the neighbors you're affecting.

I'd prefer to add actions like window-height-increase-up and window-height-increase-down. Both of them increase window height, but the first one grows the window upwards (shrinks the upper neighbor) and the second one grows it downwards (shrinks the lower neighbor).

For decreasing the height of a window, I wouldn't add new actions, to avoid too many actions. Instead, the user can switch focus to a neighbor window and grow that one to achieve the same effect.

[jinliu]

That also makes sense. But maybe we can provide 4 actions ("move top/bottom border up/down") and let the user decide what suits him better. Yes, it's a bit too many actions. But as long as we don't assign any default keybindings, it seems OK to me. In contrary, the decision to choose 2 from the 4 actions seems a bit random...

[peterfajdiga]

The decision to choose the two actions is not completely random. The window that is focused is the one that is currently being used and I think it's more likely that the user will decide they want a bigger view of the window they're using than that they want a smaller one.

But maybe having all four actions would still be useful. Either way works for me.