Sometimes panes won't expand and take up blanks

[hez2010]

Environment

Windows build number: 18363.476
Windows Terminal version (if applicable): 0.7.3291.0

Steps to reproduce

1. create lots of split panes and resize some panes.
2. run exit on some of panes to close some panes.
3. sometimes other panes won't take up the spaces of closed panes.

Expected behavior

Other panes should take up the blank space of the window after I close some panes.

Actual behavior

The blank spaces still leave blank.

However, if you resize the window, the panes will return to normal.

[zadjii-msft]

wowowow that looks really bad. Thanks for the report! This doesn't always repro, but it definitely does sometimes repro. Good enough for us to be able to investigate.

[DHowett-MSFT]

Wait, this that modern art I've been hearing so much about

[mcpiroman]

For the record, I've been seeing this for a long time, so that's not something recent. I must have forgotten to file an issue.

[mcpiroman]

I thing I've found the cause. But first, the simplest possible repro:

1. Split pane
2. Split the right pane
3. Close the left-most pane

This happens when neighbour of closed pane is a pane in 'parent' state. It won't get resized, because it's children's are sizes are specified by fixed pixel amount. By contrast, a 'leaf' pane does resize, because the terminal control inside is set to fill the grid.
I don't quite understand the intent of #3996 (comment), but that seems like the ideal solution for this issue.

[zadjii-msft]

@mcpiroman Ooh, that's a really good catch. That comment probably will fix this. Thanks!