Scroll-bar scrolling in Mac (CARBON) Emacs

[Lennart Staflin]

I have notice some scrolling misbehavior in Emacs on a Mac (CARBON, 
recent CVS checkout).

Scrolling thru a buffer using the scroll bar sometimes stops working 
and instead echoes events to the echo area:

 "vertical-scroll-bar double-down-mouse-1 double-mouse-1 ..."

Event keyboard events get echoed and ignored. It seems to be triggered 
by a double click (easy to do a double click when scrolling thru a 
buffer.)

I looked a bit closer to what happens and it seems that 
mac-handle-scroll-bar-event gets called with the double-down-mouse-1 
event and then calls mac-scroll-up that reads events and discards them 
until it gets a mouse-1 event.

As far as I can tell, mac-handle-scroll-bar-event is only bound to 
down-mouse-1. But I think that double click events get simplified if 
they have no binding, so calling the function with the 
double-down-mouse-1 would be expected. Then the mac-scroll-* functions 
are in error, they can't just look for a mouse-1 event.

It is unclear to me what the purpose is of turning on mouse tracking 
and discarding events. It seems to me to work well with out that. I.e. 
with simply:

(defun mac-scroll-down ()
  (scroll-down))
etc.


//Lennart Staflin