Return DELTA if WINDOW can be resized vertically by DELTA lines.
WINDOW must be a valid window and defaults to the selected one.
Optional argument HORIZONTAL non-nil means return DELTA if WINDOW
can be resized horizontally by DELTA columns. A return value of
zero means that WINDOW is not resizable.
DELTA positive means WINDOW shall be enlarged by DELTA lines or
columns. If WINDOW cannot be enlarged by DELTA lines or columns,
return the maximum value in the range 0..DELTA by which WINDOW
can be enlarged.
DELTA negative means WINDOW shall be shrunk by -DELTA lines or
columns. If WINDOW cannot be shrunk by -DELTA lines or columns,
return the minimum value in the range DELTA..0 that can be used
for shrinking WINDOW.
Optional argument IGNORE non-nil means ignore restrictions
imposed by fixed size windows, `window-min-height' or
`window-min-width' settings. If IGNORE is a window, ignore
restrictions for that window only. If IGNORE equals `safe',
live windows may get as small as `window-safe-min-height' lines
and `window-safe-min-width' columns. Any other non-nil value
means ignore all of the above restrictions for all windows.
Optional argument TRAIL `before' means only windows to the left
of or below WINDOW can be shrunk. Optional argument TRAIL
`after' means only windows to the right of or above WINDOW can be
shrunk.
Optional argument NOUP non-nil means don't go up in the window
tree but check only whether space can be obtained from (or given
to) WINDOW's siblings.
Optional argument NODOWN non-nil means don't go down in the
window tree. This means do not check whether resizing would
violate size restrictions of WINDOW or its child windows.