Name: PGSCRL
Purpose: scroll window
Category: GRAPHICS
File: pgplot.src
Author: T.J. Pearson
Use: see description below.
Description:
SUBROUTINE PGSCRL (DX, DY)
REAL DX, DY
This routine moves the window in world-coordinate space while
leaving the viewport unchanged. On devices that have the
capability, the pixels within the viewport are scrolled
horizontally, vertically or both in such a way that graphics
previously drawn in the window are shifted so that their world
coordinates are unchanged.
If the old window coordinate range was (X1, X2, Y1, Y2), the new
coordinate range will be approximately (X1+DX, X2+DX, Y1+DY, Y2+DY).
The size and scale of the window are unchanged.
Thee window can only be shifted by a whole number of pixels
(device coordinates). If DX and DY do not correspond to integral
numbers of pixels, the shift will be slightly different from that
requested. The new window-coordinate range, and hence the exact
amount of the shift, can be determined by calling PGQWIN after this
routine.
Pixels that are moved out of the viewport by this operation are
lost completely; they cannot be recovered by scrolling back.
Pixels that are ``scrolled into'' the viewport are filled with
the background color (color index 0).
If the absolute value of DX is bigger than the width of the window,
or the aboslute value of DY is bigger than the height of the window,
the effect will be the same as zeroing all the pixels in the
viewport.
Not all devices have the capability to support this routine.
It is only available on some interactive devices that have discrete
pixels. To determine whether the current device has scroll capability,
call PGQINF.
Arguments:
DX (input) : distance (in world coordinates) to shift the
window horizontally (positive shifts window to the
right and scrolls to the left).
DY (input) : distance (in world coordinates) to shift the
window vertically (positive shifts window up and
scrolls down).
Updates: Oct 16, 1998: JPT automatically extracted from source.