There were three separate clauses in the WM_SIZE message handler which
potentially called term_size() to resize the actual Terminal object.
Two of them (for maximisation and normal non-maximised resizing drags)
first checked if an interactive resize was in progress, and if so,
instead set the need_backend_resize, to defer the term_size call to
the end of the interactive operation. But the third, for
_un_-maximising a window, didn't have that check.
As a result, if you start with a maximised window, drag its title bar
downward from the top of the screen (which unmaximises it), and
without letting go, drag it back up again (which maximises it), the
effect would be that you'd get one call to term_size in the middle of
the drag, and a second at the end. This isn't what I intended, and it
can also cause a redraw failure in full-screen applications on the
server (such as a terminal-based text editor - I reproduced this with
emacs), in which after the second term_size the terminal doesn't
manage to redraw itself.
Now I've pulled out the common logic that was in two of those three
pieces of code (and should have been in all three) into a subroutine
wm_size_resize_term, and arranged to call that in all three cases.
This fixes the inconsistency, and also fixes the emacs redraw problem
in the edge case I describe above.
07d334c61d