Polling the mouse
jphurley at jps.net
Thu Feb 21 11:14:01 EST 2002
Jim Hurley wrote:
>> I regularly use "repeat until the mouseClick" without the same
>> problems I experience with the mouse function. My question is: Does
>> the advice to stay away from polling the mouse extend to the
>> mouseClick function as well? Scott has warned that the mouse()
>> function may/will be discontinued. How about mouseClick()? Is it also
>> in jeopardy?
Scott Rainey wrote:
>Yes. The full list of functions to avoid because they are deprecated is:
>And the very worst thing to do with any of these is "repeat until
><function>", which will condemn you to the fires of eternal damnation
>in multiuser hell ;-)
>The last 3 can be safely acquired with "the keysDown", but be careful
>to not sit in a repeat loop calling that or you may hang your app or
>at the very least have the gods of multiuser development strike you
>And while we're on the subject of bad technique that will cause you
>grief at some point, also avoid using the following messages:
>That's it. Not a long list, and in all cases it's very easy (I would
>even in most cases say trivial) to do it the right way. A small price
>to pay for shrugging off the last of the circa 1984 single-user
>single-tasking design of MacOS and HyperCard.
After 35 years as a professor of physics, it has been my experience
that trivial is in the mind of the beholder.
Scott is quite right is pressing *developers* not to anger the "gods
of multi-user development." But there is also another class of user,
one to which Run Rev is trying to appeal, and that is the *student*
who is using HyperTalk as a computer language--perhaps as young as
eighth grade. And this user would be programming in the development
environment and would be unconcerned with tying up the CPU.
For some time I have been using HC, MC and/or RR to build Turtle
Graphics into HyperTalk and allow grade school students to use the
package to program their own solutions to problems in mathematics and
physics. There are two areas in this work in which HyperCard is quite
superior to MC or RR. (And there are many others, of course, in which
MC and RR are infinitely superior to HC.) The most serious problem is
the glacial speed with which MC draws images (in many cases this
problem is lethal) and the second, and much less important, is the
problems students have in polling the mouse.
There appears to be no remedy in the offing to the speed problem.
However, regarding mouse-polling, my earlier question dealt with the
reliability and continued viability of the mouseClick function.
As an example, students create a button which, when clicked, sends a
satellite on its way into orbit around the earth--leaving a line in
its wake to show the trajectory. (The student has programmed the
turtle to obey the laws of Newtonian gravity.) When the student is
satisfied with the length of the trajectory, he or she clicks again
(anywhere on the screen) to stop the process. This is accomplished
with a "repeat until the mouseClick" or "if the mouseClick then exit
So my question is three-fold:
1. Is this a reliable operation given the current state of the MC
engine? That is, is there a bug similar to that in "repeat until the
mouse is down?"
2. We know that we may lose the mouse() function in the future. Is
mouseClick vulnerable as well?
3. If mouseClick will not be an option, what is the work-around so
that the student may click anywhere on the screen to exit a repeat
loop, and hopefully one which is simple enough for an eighth grader
to discover? (Since the student clicked the button to start the
process, it is more natural to click again to stop the process. It
would be awkward to have to move to the keyboard.)
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