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Re: making something autoexecute before normal execution

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  • Subject: [mg116866] Re: making something autoexecute before normal execution
  • From: John Fultz <jfultz at>
  • Date: Thu, 3 Mar 2011 05:55:26 -0500 (EST)

On Wed, 2 Mar 2011 04:35:02 -0500 (EST), David Bailey wrote:
> On 01/03/2011 10:25, David Bailey wrote:
>> However, I find that there are a lot of circumstances in which
>> Mathematica seems frozen - too frozen to quit the kernel via the menu -
>> where it is possible to recover the FrontEnd by killing the kernel
>> process some other way. I have an icon to do this using the Windows
>> taskkill.exe program. Very occasionally this simply crashes the
>> FrontEnd, but I would say it is 95% successful.
> As an example, execute the following line of code and press the button.
> Button["Clear",If[ChoiceDialog["Are you sure?"],Print["Doing it"]]]
> The FrontEnd will hang (for no obvious reason!), but you can recover if
> you kill the kernel as described.
> David Bailey

David, I think, already knows this...but for those who don't, the way
to workaround this is to add the option


to the Button expression.  That totally erases any hangs which might
happen, but it also puts the evaluation in the same queue as Shift+Enter
evaluations, which means it may take a considerable time for the button
to respond if other activities are in the queue.

The behavior in this case is not merely a minor implementation bug, but
springs from some core design decisions about how to do evaluations in
interfaces (Buttons, Dynamics, EventHandlers) which can interrupt ongoing
kernel evaluations and which should be resolved ASAP.  The best that I
can say here is that we continue to think and ponder over these issues.

As for the original email, if you can reproduce any cases where the FE
is hung or you're unable to kill the kernel, please report them to tech
support.  Even in the worst cases of the sort that David describes, the
FE is supposed to wake up after a generous 6 seconds of waiting around
for the kernel to do these sorts of evaluations and clean things up.
If it doesn't, then that's definitely a bug we're interested in.


John Fultz
jfultz at
User Interface Group
Wolfram Research, Inc.

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