kresch@vu-vlsi.Villanova.EDU (Ed Kresch) (10/15/89)
According to Inside Macintosh Volume I (P. 37) the criteria for a successful
double-click are:
"If the downstroke of the second click follows the upstroke of the
first by a short amount of time (as set by the user in the Control
Panel), and if the locations of the two clicks are reasonably close
together, the two clicks constitute a double-click."
I have noticed that very few applications follow this rule. In fact, none
of the versions of the Finder I have used over the years have used it, either.
The rule clearly stipulates that the time is computed from the most recent
mouse up event to the current mouse down event. What the Finder does is
compute the time from the previous mouse down event to the current mouse
up event (i.e., mouse down, mouse up, mouse down, mouse up). In system
subroutines, such as SFGetFile, it seems to use the time from the previous
mouse down event to the current mouse down event, but the action is delayed
until the mouse is released. The only case I have been able to find that
actually seems to follow the guidelines is in MacWrite when double-clicking
a word.
Admittedly, I have not done exhaustive testing on all my programs and their
subroutines. Nevertheless, considering the variety I have found in just
the few I have tested, I am curious if there are any firm guidelines on
what consitutes double-clicking. Anyone have any information on this?
Thanks.
Ed Kresch