Klapauzius wrote on 18.04.12 at 21:37:49:

This routine sets up the keyboard controler to report absolute mouse packets. It's not a check routine. The ikbd in the ST has two ways of reporting mouse actions by the user: - the usual 'relative' mode, which will report delta values when the mouse is being moved (for example mouse has been moved 2 pixels up, etc.). In the relative mode each mouse action will automatically trigger an interrupt by the ikbd. and - the 'absolute' mode which is activated in your routine. This mode will send absolute mouse coordinates, not deltas. Important: in this mode you won't get an automated report when the mouse is moved or a button is pressed. To get the current mouse position and button status you will have to inquire the mouse state. This is done by sending a $d byte to the ikbd, which will in turn generate an interrupt by the ikbd. Like in the code snippet you asked about on Atari-Forum.  ;) $9 will activate this absolute mouse mode. The next four bytes sent afterwards define coordinate range. The $c byte + the two bytes following set up the 'scale factor'. This will define how far the mouse must be moved by the user for a increment/decrement in the absolute coordinates to occur. The $e byte + the rest will load an initial position for the mouse. Read all about it here: http://d-bug.mooo.com/dbugforums/cgi-bin/yabb2/YaBB.pl?num=1280676368  :)

Thanks for that, so once that routine has been called, the interrupt at $118 then gets activated.

Does that interrupt stay active or does it automatically close when a mouse event has occured?

This is all completely bloody new to me!