Right now, on the top and right edges, the behavior is strange.
On the right side, the main map viewport ends 128 pixels from the
right edge of the window, because the rightmost 128 pixels of space is
used for the minimap and controls area. When you position the mouse
near the right edge of the entire window, the main map viewport starts
scrolling. This is strange because you have to move the mouse *way*
out of the main map viewport for this to happen. It would make more
sense if this auto-scrolling behavior started when you moved the mouse
cursor to the right edge of the main map viewport, rather than having
to move it an extra 128 pixels to the right edge of the window.