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Re: Problems with ChoiceDialog inside a Dynamic: Bug or

• To: mathgroup at smc.vnet.net
• Subject: [mg107783] Re: [mg107725] Problems with ChoiceDialog inside a Dynamic: Bug or
• From: Adam Griffith <adamg at wolfram.com>
• Date: Thu, 25 Feb 2010 17:38:38 -0500 (EST)
• References: <201002250649.BAA20530@smc.vnet.net>

ChoiceDialog[] blocks the kernel evaluation until it is closed. Therefore you could do something like:

TabView[{"Tab1" -> 
   Button["Show ChoiceDialog", 
    result = ChoiceDialog["This holds eval.. :-)."], 
    Method -> "Queued"], 
  "Tab2" -> 
   Button["Show MessageDialog", MessageDialog["This works!"];]}]

-Adam





Guido Tripaldi wrote:
> Hi Group,
> suppose you wanna to display an alert to the user before to continue the 
> execution of your code when some conditions occur : probably you'll use 
> ChoiceDialog[], the useful function that "puts up a standard choice 
> dialog that displays  expr together with OK and Cancel buttons, and 
> returns  True if OK is clicked, and  False if Cancel is clicked.".
>
> But if you use this function inside some Dynamic[] object, it hangs the 
> kernel. I've tried to find in the documentation some references to this 
> bad combination without any luck, so I don't understand if this is a bug 
> or there is something missing in the code.
>
> To better explain the problem here is a very basic example:
>
> (* just a silly example *)
> Grid[{
>   {"Choose a dividend: ",
>    PopupMenu[Dynamic[dividend], Table[i, {i, 0, 10}]]},
>   {"Choose a divisor : ", PopupMenu[Dynamic[divisor], Table[i, {i, 0, 10}]]},
>   {"Quotient: ", Dynamic[dividend / divisor]}
>   }, Frame -> All]
> Dynamic[
> If[divisor == 0,
>    ChoiceDialog["Uh-oh, you are going to do a division by zero! Please select a different divisor.", {"Ok"}];
> ]];
>
> Instead, if you use the MessageDialog[] function to show a message window, all works well, but of course the execution will continue without waiting for the user action (that is not what I want).
>
> Same situation if you try to use ChoiceDialog[] inside a TabView, or other kind of Views:
>
> (* another silly example *)
> TabView[{
>   "Tab1" -> Button["Show ChoiceDialog", result = ChoiceDialog["This hangs.. :-(."];],
>   "Tab2" -> Button["Show MessageDialog", MessageDialog["This works!"];]
>   }]
>
>
> Any suggestion?
> thanks!
>    G
>
> ps
> M7.0.1.0 on Mac Snow 10.6.2
>
> ---
> Guido Tripaldi
>
>
>   

• References:
  • Problems with ChoiceDialog inside a Dynamic: Bug or not (well) documented limitation?
    • From: Guido Tripaldi <guido@gtripaldi.it>