ggiWaitRayPos - Wait for the raster to reach a point
int ggiWaitRayPos(ggi_visual_t src, int32_t* x, int32_t* y);
ggiWaitRayPos will wait, as best supported by the target, until the
raster reaches a certain point on the screen. Actual integer
coordinates don’t mean anything under current implementations, and the
units the coordinates are provided in haven’t been firmly decided.
Instead, use one of the following macros: GGI_RP_BORDER means the
raster is in the border of the screen; GGI_RP_BLANK means the raster is
past the border and is turned off; GGI_RP_SYNC means the raster is
retracing to the top of the screen; GGI_RP_DONTCARE means you don’t
care where the raster is in this direction.
0 for OK, otherwise an ggi-error(3) code. In the event that there is
an error, it is most likely that the implementation on the given target
is limited. In this case, the parameters x, y will be assigned values
equal to one of the above macros, which should work on the target,
supposing using those values actually accomplishes what you want to do.