bug#38181: Actual height of mode-line not taken into account

[martin rudalics]

>>   > I think fit-window-to-buffer relies on window's metrics (like the
>>   > number of lines in the text area) to be up to date, and that is only
>>   > true after a window was redisplayed once since changing the mode-line
>>   > height.  Martin, is this correct?
>>
>> Yes.
>
> Then I'm not sure we can fix such use cases at all, without causing
> display flickering in much more popular use cases.  Do you have any
> ideas for a possible fix?  Could fit-window-to-buffer invoke
> 'redisplay' internally, perhaps?

It could but it's called way too often to warrant such behavior by
default.  But we could give it a separate optional argument so users
can avoid the advice.  I think Jonas could easily write and a test a
patch along this idea.

>> But, as I mentioned earlier, the problem shows up with the
>> scroll bar immediately when Jonas' form is evaluated, see the attached
>> screenshot.
>
> That just means we (or a Lisp program which makes these mode-line
> modifications) need to recreate and redisplay the scroll bars anew in
> these cases, right?

Right.  But that same program could also redisplay all windows in
these cases, right?

> It's a separate problem, right?

For some value of right ...

martin