This is in response to Peter Summers' observation in
http://lists.wfu.edu/pipermail/gretl-users/2014-December/010481.html
It's a long story but I'll try to be brief.
Prior to gretl 1.9.91 we had a mechanism that appeared in the 
menubar of a script editor window to indicate progress when a script 
took appreciable time to complete: a "spinner" plus a "stop" button 
that could be used to halt execution of the script. (At that time 
the output window didn't appear until execution of the script was 
finished.)
More recently, I figured it was preferable to open a script output 
window right away, and show the spinner + stop-button in that 
window. In this way, we could arrange for partial output to appear 
as it was produced, giving a more convincing impression that 
progress was being made (see the newish "flush" command).
That worked up to a point, but after Peter's comment I realized that 
the policy "open an output window right away and show a spinner and 
stop-button there" was not always engaged; it depended, in a way 
that I hadn't intended, on certain user choices.
I think this is now fixed in CVS and snapshots. Testing would be 
welcome. If you run a time-consuming script in the GUI you should 
see the output window "come to the front" with spinner and stopper. 
(But if the script completes quickly you probably won't notice 
this.)
This is quite tricky to code, and I'd be particularly interested if 
anyone is able to provoke a crash (e.g. by pressing the stop 
button).
Allin Cottrell