Re: Simplification to mouse-avoidance-mode (patch) + redisplay bug?

[Jan Djärv]

Kim F. Storm skrev:

> I've debugged this far -- and need an X-pert (Jan?) to take over:
>
>
> mouse-avoidance-mode 'animate uses set-mouse-position to move
> the mouse cursor in ~10 steps to reach its end position.
>
> If I type very slowly, approaching the window cursor to the mouse
> cursor -- and don't type anything while the mouse cursor is moving,
> everything works, i.e. the mouse cursor shape at the final destination
> is ok.
>
> If I type more quickly, the mouse cursor still moves in steps, but
> it may end up with any of the cursor shapes it had along the path.
>
> I put some trace output into xterm.c, and it seems that (in the first
> case) for each call to x_set_mouse_position (which calls
> XWarpPointer), the event loop receives a MotionNotify event
> (event.type = 6) with the new mouse cursor position.
>
> .. unless I hit a key while the mouse is moving (the second case).
>
> As soon as emacs gets the key event (event.type = 2), no further
> MotionNotify events are delivered for the remaining mouse positions
> along the path.
>
> This looks like an X bug.  This is the Xfree server from redhat 9.0.

Are you sure x_set_mouse_position is called?  When I hold down a key and let 
it repeat, mouse avoidance is not working at all (i.e. x_set_mouse_position is 
not called).  I suspect event processing takes all time so mouse avoidance 
does not get time to check where the cursor is.

Another thing is that X is not guaranteed to deliver MotionNotify for every 
pixel the mouse moves through.  It is actually undefined how many MotionNotify 
you will get when moiving the mouse, but you are guaranteed to get one 
MotionNotify when the mouse movement stops.

A third thing to check is if the XWarpPointer requests are queued or not.  You 
can add a call to XFlush after XWarpPointer and see if that improves the 
situation.

I tried, but could not reproduce the situation where the cursor shape is 
wrong.  I'm sure it is timing related, i.e. events not sent or received when 
expected to.

        Jan D.