[Freeciv-Dev] (PR#6810) map_canvas_expose is inefficient

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://rt.freeciv.org/Ticket/Display.html?id=6810 >

In gui-gtk-2.0 (and probably others) map_canvas_expose is called any 
time _part_ of the mapview is exposed.  It draws the update to the 
window, as it is supposed to do.

It also does other junk, like doing a few boolean checks (which may 
occasionally pass and result in more processing being done).  No problem 
there.

And is calls refresh_overview_canvas.  This is a big problem.  In 
gui-gtk-2.0, since map_canvas_expose is called (possibly multiple times) 
for every flush, this is HIDEOUSLY inefficient.

jason