Stack check-out/check-in

[Alex Tweedly]

which is fine if you are OK doing manual clean-up when, not if, if the 
stack should ever exit without 'quit'ing, or become disconnected from 
the network, or ... any of which would leave the file-flag behind.

The  easiest alternative is to have the stack update the file 
periodically, and instead of checking for the file's existence, check 
how up-to-date it is. Do the update this periodically (maybe every 
minute, every 5 minutes , ...) and if the file exists but is old by more 
than 3 * the chosen interval then delete the file and continue.  (And do 
be careful of time drift between different machines).

Alex.

On 26/01/2021 01:06, Paul Dupuis via use-livecode wrote:
> If the could storage the stack is on has write access, the easiest 
> mechanism is a file based flag.
>
> When the stack is launched, if checks:
>
> if there is a file <filespec> then
>   -- the stack is already open, so exit
> else
>    put empty into URL ("file:"&<filespec>) -- creates a empty file to 
> mark as open
> end
>
> and  when the stack exists remove the file
>
> on quit
>   delete file <filespec>
> end quit
>
> Or something like that. I do not have LC open to check my code above.
>
>
> On 1/25/2021 7:24 PM, Marty Knapp via use-livecode wrote:
>> I have an app that allows user to create specialized editable 
>> documents (stacks) that open in my app. Some customers use Dropbox, 
>> iCloud, OneDrive or similar to store these documents so that they can 
>> be accessed from 2 different computers. Is there a way to tell if a 
>> stack is already open on one computer? I need to prevent them from 
>> opening a 2nd instance of the stack on the other computer so that 
>> Dropbox (or other cloud sync service) does not create a conflicted copy.
>>
>> If there is not a way to tell, has anyone created some sort of stack 
>> check-out/check-in system that they'd be willing to share? I need 
>> this for Mac, PC and mixed.
>>
>> Marty
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