When you copy pixels to a surface using either IDirectDrawSurface7::Blt or IDirectDrawSurface7::BltFast, the method might fail with DDERR_WASSTILLDRAWING because the hardware blitter was not ready to accept the command.

If your application has no urgent business to perform while waiting for the blitter to come back into a state of readiness, you can specify the DDBLT_WAIT flag in the dwFlags parameter of Blt, or the equivalent DDBLTFAST_WAIT flag for BltFast. The flag causes the method to wait until the blit can be handed off to the blitter (or until an error other than DDERR_WASSTILLDRAWING occurs).

Blt accepts another flag, DDBLT_ASYNC, that takes advantage of any hardware FIFO (first in, first out) queuing capabilities.

When you copy pixels to a surface using either DirectDrawSurface7.Blt, DirectDrawSurface7.BltColorFill, DirectDrawSurface7.BltFast, DirectDrawSurface7.BltFx or DirectDrawSurface7.BltToDC, the method might fail and raise a DDERR_WASSTILLDRAWING error because the hardware blitter was not ready to accept the command.

If your application has no urgent business to perform while waiting for the blitter to come back into a state of readiness, you can specify the DDBLT_WAIT flag in the flags parameter of Blt, or the equivalent DDBLTFAST_WAIT flag for BltFast. The flag causes the method to wait until the blit can be handed off to the blitter (or until an error other than DDERR_WASSTILLDRAWING occurs).

Blt accepts another flag, DDBLT_ASYNC, that takes advantage of any hardware FIFO (first in, first out) queuing capabilities.