Quitting standalone, is this a bug?

[Devin Asay]

Hi Michael. Welcome to the list.

On May 17, 2007, at 10:21 AM, Michael Binder wrote:

> Hi everyone,
>
> This is my first post to this list.  I'm new to Rev (but much  
> hypercard experience).  I have just spent a couple of days figuring  
> something out (it may be a bug) so I thought I'd share it.  I am  
> developing with Studio 2.81 and testing on an mac ibook G4 running  
> 10.3.9.
>
> To demonstrate the bug:
> Step 1) create a new main stack and call it "myApp".
> Step 2) Put this handler into the stack script:
>
>   on shutdownrequest
>      answer "This stack: "& the name of this stack &cr& "Quit now?"  
> with "Yes" or "No"
>      if it is "Yes" then pass shutdownrequest
>   end shutdownrequest
>
> Step 3) Save myApp, and then save it as a mac OS X standalone.
> Step 4) Launch the standalone.
> Step 5) Quit (by menu or commandkey Q) and choose "No".  (the  
> behavior is as expected)
> Step 6) Quit again.  This time the bug is evident...
>
> On my system, the second (and all subsequent) quit brings up a  
> dialog box with an unexpected result: This stack: stack "answer  
> dialog"

This is probably more an unexpected result than a bug. The problem  
seems to be caused by the nature of the message hierarchy. Every  
window in Rev is a stack, including the answer dialog, and every time  
you try to quit the Rev engine, a shutdownrequest will be sent to the  
current stack. If it's not handled by that stack it'll pass up the  
hierarchy until it finds a handler.

You might try this and see what happens:

   answer "This stack: " & the mainstack of this stack & cr & "Quit  
now?" etc.

You could also try putting one or more exceptions in your  
shutdownrequest handler:

   if the style of this stack is topLevel then -- would only execute  
if the stack receiving the shutdownrequest was non-modal.

   if the visible of this stack then -- would ensure shutdownrequest  
would only be handled in a visible stack

Or a combination of the above.
>
> I discovered this bug in myBigComplexApp, and the bug there is a  
> bit different.  The first time I quit myBigComplexApp, "This stack"  
> is "revExternalLibrary".  On the second and all subsequent quits  
> "this stack" is "answer dialog". (as in the example above)
>
> This is a problem for me because when a user quits myBigComplexApp  
> I need to validate data and offer the user a chance to save the  
> changes.  In order to do this I need to determine what data entry  
> card the user is viewing when the quit request occurs:
>
>    on shutdownrequest  -- this does not work as expected because of  
> the bug
>       if the short name of this cd is "dataEntry1" then
>         validateData1
>       else if the short name of this cd is "dataEntry2" then
>         validateData2
>       end if
>       offerChanceToSave
>    end shutdownrequest
>
> My workaround for the bug is as follows:
>
>    on shutdownrequest
>       put line 1 of the recentcards of stack "myBigComplexApp" into  
> whichcard
>       if the short name of whichcard is "dataEntry1" then
>         validateData1
>       else if the short name of whichcard is "dataEntry2" then
>         validateData2
>       end if
>       offerChanceToSave
>    end shutdownrequest
>
> I am not all that confident in my workaround because I am not  
> confident that I understand the nature of the bug.  As I mentioned  
> above, the bug in (simple) myApp is a bit different than in  
> myBigComplexApp.
>
> Do any of you have any thoughts on whether this is a bug, whether  
> it occurs on other platforms, and whether my workaround could be  
> improved?

Would it work to do data vaildation on closeStack instead of  
shutdownrequest?

HTH

Devin

Devin Asay
Humanities Technology and Research Support Center
Brigham Young University