The way the first Gaddis book examples are structured is not the recommended way of using Dark GDK. Usually you have a loop and use dbSync to update the screen. (However, recommended or not, this should still work.)
Do you have NVidia video card? If yes, you might be affected by this bug.
http://forum.thegamecreators.com/?m=forum_view&t=158209&b=15
The circles show up all right on a computer with ATI video card. One thing you can try is to change the program the "recommended way" and redraw your circles every loop like this:
#include "DarkGDK.h"
void DarkGDK()
{
// Variables for the center points.
int x = 319, y = 239;
// Draw concentric circles.
while (LoopGDK()) {
for (int radius = 50; radius <= 200; radius += 50)
dbCircle(x, y, radius);
dbSync();
}
}
If that fails as well, here are some workaround functions that you can use instead of dbCircle and dbEllipse. (And please, if the above code still doesn't show any circles on your machine and you do have an NVidia card, then add your experience to the problem report thread.)
http://forum.thegamecreators.com/?m=forum_view&t=158250&b=22&p=0
