When resizing rootston with the mouse, the result is really slow. One
can see that rootston needs quite a while for drawing the newly visible
area. This is because every single expose event is handled on its own
and causes (apparently) a full repaint or at least a swap.
This commit improves things by only causing a new frame if none is
pending already.
With this change, there is almost no delay in rootston drawing the newly
visible area.
Signed-off-by: Uli Schlachter <psychon@znc.in>
e79d924588