Plotting bitmaps

[KeepingRealBusy]

I have developed a program that plots bitmaps. No big deal. It almost works, but has a few things that are not quite what I expected. I added breakpoints to the code.
The breakpoints take and get me into VS, but If I minimize VS (full screen) temporarily to see the plotted lines, the plotted lines on the bitmap (full screen) show nothing (I get a title bar and I get some of my initial black lines to frame the plotting area into two horizontal boxes but none of the red or blue lines following that).
What do I have to do to both take breakpoints and also be able to see what has been plotted?

If I free run, and then hang in a loop, the plotted red and blue lines show up, but the lines seem to have a stray bit or two added just above the top and I was trying to trap where this was coming from. Also, I noticed that the lines seemed to not be drawn down to the middle dividing line, but they should have been.

There has to be some Windows API that must be called to force the display before the breakpoint - but what is that?

Dave.