VScrollImage - scrolls an image in two dimension.
VScrollImage(win, image, x1, y1, delta_x, delta_y)
int x1, y1;
int delta_x, delta_y;
VScrollImage scrolls an image in two dimensions in the image window or
one of its subwindows according to delta_x and delta_y.
0 - work successfully.
6 - invalid window ID.
win - the image window or one of its subwindows.
ximage - specifies the image to be scrolled (already displayed with
x1, y1 - specifies x and y coordinates of the upper left corner of the
image, relative to the origin of the specified window before
delta_x, delta_y - the offset between the old image position and the new
Any other graphics on top of the image in the window will move with the
image but will be lost if hidden.
If VCreateColormap is not called earlier, or the image to be scrolled is
totally out of the specified window boundary, VScrollImage prints an error
message to the standard error stream, produces a core dump file and exits
from the current ptocess.