Get program control if user is inactive

Execute some code after a given number of seconds, when the user does not interact with the program.

When to use the ON IDLE trigger?

If an interactive instruction has the control, the program waits for a user interaction like an action or field input. If the end user leaves the workstation, or switches to another application, the program cannot get the control and is frozen until the user comes back. You might want to execute some code, after a period of inactivity, for example to refresh the displayed data by doing a new database query, or even after a long period, to terminate the program automatically.

Implementing the ON IDLE trigger

To detect user inactivity during a dialog, define an ON IDLE trigger in the dialog. This trigger is dialog specific, it is typically defined in the main dialog of the program, but it can also be defined in every dialog.
  • Consider using the ON IDLE only in dialogs that do not handle field input, such as DISPLAY ARRAY and MENU. If used in input dialogs, this trigger may execute while the current field contains an incomplete value. The trigger will produce field value validation and raise an input error. However, ON IDLE can be used in input dialogs where the user cannot enter invalid values (for example when using CHECKBOX, RADIOGROUP, COMBOBOX, and character-type fields like TEXTEDIT).
  • When implementing multiple dialogs with DIALOG block, do not mix several ON IDLE clauses in different sub-dialog blocks: specify a unique ON IDLE clause at the DIALOG block level.
  • Obviously, it does not make much sense to mix ON TIMER and ON IDLE clauses.
For example:
LET seconds = 120
   ON IDLE seconds
      MESSAGE "Automatic data refresh..."
      -- Reload the array with a new database result set

Note that the parameter of the ON IDLE trigger can be an integer variable, but it will only be read when the dialog is started. Changing the variable during dialog execution will have no effect.

A value of zero or less than zero disables the timeout trigger.