This command opens a tile scrolling
canvas with the effective size of the total map, but an actual
size of only just a little larger than the viewport. This means
that as far as you are concerned you have a large canvas to scroll
around, however, in terms of memory it only opens a small canvas.
The map used is the currently
loaded map. If the canvas is open, it is closed and reopened
to be just larger than the viewport size. This canvas is managed
by the viewport, you can draw on the canvas yourself,
but your changes will just be erased whenever you scroll enough
for the map to be redrawn.
If you change the tiles on the
map with the 'set map tile' command then the tiles will be updated
in the viewport. If you change the currently loaded map then
the viewport will redraw with the new map.
When doing tile scrolling, you open a canvas just a
little larger than the viewport and then scroll only by a few
pixels before resetting the scroll back to zero and redrawing
the map tiles 1 tile over. This allows a huge map to be scrolled
without having to open a canvas as big as the map.
Using a map viewport is a lot
easier than doing tile scrolling yourself, TNT Basic takes care
of all the map redrawing and scrolling offset for you, you just
treat the canvas as a huge canvas the size of the map. You can
position your sprites anywhere on the map without having to worry
about doing the same coordinate transforms you'd have to perform
if doing manual tile scrolling.
The viewport can be removed
from the display with the function Close
Viewport and scrolled using Set