Creating a warning before executing a function if not cancelled?

Question

How could I create a warning dialog that executes a function if not cancelled after a delay ? Also I would like the time remaining before execution to be displayed and the dialog to be non blocking.

Answer 1

I think this does what you want:

SetAttributes[countdownConfirm, HoldRest]

countdownConfirm[msg_, body_] :=
  CreateDialog[
    Column[{
      Row[{msg, " ", 
       Dynamic[If[# > 0, #, DialogReturn[body]; #] & @ 
        Ceiling @ Clock[{5, 0}, 5, 1]]}],
      CancelButton[]
    }]
  ]

Test:

countdownConfirm["A print will happen in", Print@"A print happened indeed!"]

Answer 2

Using the function below we can do:

ExecuteIfNotCanceled["A print will happen in",Print@"A print happened indeed!"&]

This function is interesting as it uses many different aspects of Mathematica.

ExecuteIfNotCanceled[message_,function_,delay:_Integer:5]:=
    DynamicModule[{n=delay,decrementTask,closeScheduledTask,dialog,tasks},

        tasks = {decrementTask,closeScheduledTask};

        decrementTask=CreateScheduledTask[n--];         

        closeScheduledTask=
            CreateScheduledTask[
                NotebookClose@dialog;
                RemoveScheduledTask /@ tasks;
                function[];
                ,
                {delay}
            ];

        StartScheduledTask /@ tasks;

        dialog=
            CreateDialog[
                Column[
                    {
                        Dynamic[message~~" in "~~ToString@n~~" seconds.",TrackedSymbols:>{n}]
                        ,
                        CancelButton@DialogReturn[RemoveScheduledTask /@ tasks]
                    }
                    , 
                    Alignment -> Right
                ]
                ,
                Modal->False
            ];
    ];