fix: check if tabline is present when calculating certain layouts

[l-kershaw]

• Don't include tabline in the height of the window when present.
  • Only applies to horizontal, vertical and center strategies (also inherited by flex)
• Tweaks height calculation for center strategy

Closes #995

[l-kershaw]

I've removed the tweak for the center strategy.
I think I want the tweak to be more precise, and also apply it to some other layouts, so will put it in a separate PR when I get a chance.

[l-kershaw]

I've found a problem with the vertical strategy, and some other refactoring to do.
Will hopefully fix today

[Conni2461]

Are you still working on this?
My comment would be. "I think i see a reoccurring pattern, maybe a short local function(max_lines) -> max_lines, tbln"

Otherwise LGTM (you dont need to do it. I shouldn't be that nitpicky)

[l-kershaw]

@Conni2461 I have factored out the function you suggested (good spot!), also considered factoring out the "shift down a line if have a tabline", but thought it would be more trouble than it was worth.

I'm happy with this now, but if you could have a last look over before merging, that would be great 😊

[Conni2461]

LGTM thanks :)

you can ship it if its done. I felt the same about the second refactoring. I also thought it would complicate things.