bug#59862: quit-restore per window buffer

[martin rudalics via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

 > Could you show how the frame function corresponding to 'tab-bar-close-tab'
 > (I suppose it's 'delete-frame'?)

Hardly.  'delete-frame' unconditionally deletes a frame regardless of
how many windows it displays unless it is the last frame, a surrogate
minibuffer frame or some other special condition holds.

 > detects that where are more than 1 window
 > on the frame, then it refuses to delete the frame.  Then same code could be
 > used in 'tab-bar-close-tab'.

The check is in 'window-deletable-p' which may return 'frame' iff WINDOW
is its frame's root window.  Maybe you also want to check whether the
second element of 'quit-restore' is 'frame' but that I cannot tell.

Note in this context that 'window-deletable-p' does not cover all
special cases handled by 'delete-frame' - things like the
'delete-before' parameter or the 'delete-frame-functions' hook.  So far,
this apparently has not caused any problems though.

martin