Allowing user to abort a function

[Conrad Hoffman]

I usually disable buttons and prevent the user from doing anything until whatever is currently happening, is done. I want to provide an Abort button so the user can escape/cancel an operation if desired. Let's say I'm in a sub or function, running loops, doing math, saving data to files or whatever. If the Abort button unceremoniously dumps me back to the callback function, how do I clean up the mess from whence I came? Finish storing data, close files, etc. Is there some accepted way to handle this?

[Joe Byrne]

I normally use a global variable and check it at various points in the code. When its 'set', I do whatever 'cleanup' is necessary and then exit out of the current process.

If you don't like globals, you can assign a long value to your form or to a control (like the 'abort button') and accomplish the same thing.

For what its worth, I would never use a strategy that simply bailed out of the current process. I always trap the abort flag myself and deal with it in my code. If the 'cleanup' process will be lengthy, you can popup a warning box, display a statusbar message, or do something else to indicate that the abort has been acknowledged and is being acted upon.

[Michael Mattias]

GUI + Worker Thread + Abort Demo 11-24-07

HEAVILY commented.


MCM

[Conrad Hoffman]

Thanks!

Michael- have you ever considered writing a book? You seem to have an excellent and detailed example at hand for just about everything!

CH

[Walt Thompson]

Minor Update

If you use Michael's GUI + Worker Thread + Abort Demo 11-24-07 with PB 9.0
Note that: THREAD CREATE no longer requires, or accepts, the SUSPEND argument.

Replace:

THREAD CREATE      WorkerThreadFunction (CBHNDL) SUSPEND TO hThread

With:

THREAD CREATE      WorkerThreadFunction (CBHNDL) TO hThread

[Michael Mattias]

Thank you for your kind words. Yes I did think about a book once for about 20 minutes, which is all it took to figure out I could not make any money on one.

>Note that: THREAD CREATE no longer requires, or accepts, the SUSPEND argument

Huh?

My Win 9.0 help shows syntax:

Syntax
THREAD CREATE FuncName (param) [StackSize,] [SUSPEND] TO hThread

Maybe it needs the 'empty' comma to 'hold a place' for stack size eg

THREAD CREATE FuncName (param) , SUSPEND TO hThread

Otherwise I don't know how it could tell if 'SUSPEND' is a keyword option or an invalid stack size. (Unless it assumes that 'SUSPEND' - if used - will always immediately precede the 'TO' keyword).

Of course that would make the correct syntax diagram

 THREAD CREATE FuncName (param) [StackSize] [,SUSPEND] TO hThread

MCM

[Cliff Nichols]

on this one I have to stick with MCM

from the docs
Thread Create Syntax

THREAD CREATE FuncName (param) [StackSize,] [SUSPEND] TO hThread

Thread Suspend Syntax

THREAD SUSPEND hThread TO lResult&

So I do not see where suspend is no longer supported???

[Michael Mattias]

Well, I tried eight different syntax variations with Win/9 this AM and nothing would compile, so I sent in a bug report.

Let me see if I can code up a version-testing way to do this. THis is a nice demo and I'd hate to see it obsoleted.


MCM