Comments:
The xleft, xright,
yhigh and ylow parameters
determine the actual pixels to be ren-dered. They do not affect
the scene or the view being rendered in any way, but are used to
render a rectangular portion of the view.
The rectangle selected
must be valid. That is: 0 <= xleft <xright, and 0 <= ylow
<yhigh.
NoteWhen
specified in SDL, yhigh is an absolute number, but when speci-fied
on the command line, <high> is the number of pixels of height
of the image (that is, yhigh – ylow). This is so SDL retains the
same sense as previous versions and the same sense as the interactive
package, while the command line behavior is consistent with all
the framebuffer standalones.
