And I have a vague feeling that integrating the mouse driver into the video driver is a big kick in the balls of EXOS. (What about you, Zozo?)
Driver not integrated. But when both are in the EXOS ROM, the possible call directly video driver routines.
These special function calls:
@@SIZE = 2 - return mode & size of page
@@ADDR = 3 - return video RAM address
needed, which are normaly called by EXOS 11, but EXOS call not allowed in interrupt handling. If both in same ROM then possible the direct calls.
The EXOS currently also use some direct calls, for example the KEYBOARD directly call DATE/TIME handler, when PAUSE pressed, for keep the time running. (This function missing from BRD, because it is external ROM, direct call don't possible)