C Language and Libraries Help (clang.hlp) (
Table of Contents;
Topic list)
Important Notice
The pages on this site contain documentation for very old MS-DOS software,
purely for historical purposes.
If you're looking for up-to-date documentation, particularly for programming,
you should not rely on the information found here, as it will be woefully
out of date.
Graphic Coordinate Systems
◄Up► ◄Contents► ◄Index► ◄Back►
─────Run-Time Library───────────────────────────────────────────────────────
There are three coordinate systems employed by the low-level
graphics functions. The first is the physical screen coordinate
system, where the origin (0,0) is located at the upper-left corner
of the screen and the coordinates increase downward and to the
right. All coordinates must be integral values. Only _setcliprgn,
_setviewport, _setvieworg, _getviewcoord, and _getphyscoord
require physical coordinates.
The second is the viewport (or view) coordinate system. The
graphics viewport is a clipping region with a coordinate system
origin at its upper-left corner. The default viewport is the
physical screen, until a new one is defined using _setviewport.
The viewport origin can also be reset with _setvieworg. All
coordinates must be integral values. Functions without a suffix
use view coordinates, and take shorts for coordinate arguments.
The third is the window coordinate system. The _setwindow function
transforms the current graphics viewport into a window by mapping
a real-valued coordinate system onto the viewport. Each coordinate
can have an arbitrary range specified by the _setwindow arguments.
The y coordinate can be either increasing downward or increasing
upward. Functions ending with _w use window coordinates, and take
doubles for coordinate arguments. Functions ending with _wxy take
_wxycoord structures.
For translating between the various coordinate systems, use the
_getphyscoord, _getviewcoord, and _getwindowcoord functions.
-♦-