[comp.windows.ms.programmer] BitBlt question

welter@ils.nwu.edu (Pete Welter) (01/23/91)

I am trying to display a large colored bitmap using BitBlt.
When the bitmap is drawn, it appears rather slowly in a series
of (about 4 or 5) horizontal swipes.  I have noticed the same
behavior when zooming out on this same image using MS-Paint;
seemingly the use of StretchBlt rather than BitBlt is causing this.
When the image is at normal size is MS-Paint, the drawing seems
pretty fast.

My question is: Is there any reason why BitBlt would redraw in
these horizontal strips?

Thanks!

Pete Welter
Institute for the Learning Sciences
Northwestern University
welter@ils.nwu.edu

jls@hsv3.UUCP (James Seidman) (01/26/91)

In article <703@anaxagoras.ils.nwu.edu> welter@ils.nwu.edu (Pete Welter) writes:
>I am trying to display a large colored bitmap using BitBlt.
>When the bitmap is drawn, it appears rather slowly in a series
>of (about 4 or 5) horizontal swipes...
>My question is: Is there any reason why BitBlt would redraw in
>these horizontal strips?

The BitBlt functionality is implemented by the video display driver, not
the GDI.  Are you using the standard VGA driver?  If not, you might try
switching to it and seeing if the problem goes away.  (I've never seen
the symptoms you're describing.)

-- 
Jim Seidman (Drax), the accidental engineer.
"It doesn't have to work... they'll be paralyzed just from laughing at me."
							- Dr. Who, _Shada_
UUCP: ames!vsi1!hsv3!jls	         INTERNET: hsv3.UUCP!jls@apple.com