Start floating pane at the center of the screen by default

[junegunn]

Problem Description

When you open a floating pane with the default width and height, it opens at the center of the screen.

zellij run --floating --close-on-exit -- top 

However, when you specify a non-default width and/or height, the position of the pane is not adjusted accordingly to remain centered.

zellij run --floating --close-on-exit --width 80% --height 80% -- top 

zellij run --floating --close-on-exit --width 30% --height 30% -- top 

So the users have to manually calculate the right coordinates to put it back at the center.

# (100% - 80%) / 2 = 10%
zellij run --floating --close-on-exit --width 80% --height 80% --x 10% --y 10% -- top 

This process is even more cumbersome when an absolute width or height is provided, because you need an extra step of getting the size of the terminal beforehand.

Suggestion

Always start a floating pane at the center of the screen regardless of the specified dimensions, so no manual calculation is needed.

Expected effect

Better user experience.

Alternative solution

Make --x and --y take special values like center or C, similar to -xC -yC in tmux.