Triggering User-Defined Events

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# Triggering User-Defined Events

This document covers the following topics:

- About User-Defined Events

- Passing Parameters to the Dialog

## About User-Defined Events

Aside from standard events, such as before-open, you may define user-defined events for dialogs. User-defined events are useful whenever it is necessary for one dialog to cause an action to occur in another dialog.

A user-defined event occurs whenever you have specified a `SEND EVENT` statement in dialog A with the name of a user-defined event in the target dialog B. This target dialog B for which you wish to trigger the user-defined event must already be active. You can activate dialog B by using the `OPEN DIALOG` statement. If you do not issue the `OPEN DIALOG` statement first, the `SEND EVENT` statement will cause a runtime error.

You can define your own events for dialogs by choosing the New button in the Events dialog event handler menu or from the dialog's context menu. Enter any name for your newly-defined event and specify the corresponding event section. It is recommended that this name begin with a hash (#) to distinguish your event from predefined events.

During execution of an event handler, the `SEND EVENT` statement triggers the user-defined event handler in a different dialog. After this user-defined event handler has been executed, control will be returned to the previous dialog, whose execution will resume at the statement following the `SEND EVENT` statement. This can be compared to a `CALLNAT` statement that causes a subprogram to be executed.

Similar to the `OPEN DIALOG` statement, parameters may be passed to the dialog. In order to pass parameters selectively (PARAMETERS-clause), you have to specify the name of the dialog in addition to the identifier of the dialog (operand2).

The `SEND EVENT` statement must not trigger an event in a dialog that is about to process an event. This is the case, for example, when dialog A sends an event to dialog B and the event handler in dialog B sends an event to dialog A which has not yet finished its event handling. A similar case is when dialog A opens dialog B and the before-open or after-open event contains a `SEND EVENT` back to dialog A.

To trigger a user-defined event, you specify the following syntax:

`SEND EVENT` operand1 `TO [DIALOG-ID]` operand2 |  |
|  |  |  | `WITH` operand3... `USING [DIALOG]` 'dialog-name' `WITH` PARAMETRS-clause |  |

#### Operands

Operand1 is the name of the event to be sent.

Operand2 is the identifier of the dialog receiving the user-defined event and must be defined with format/length I4. You can retrieve this identifier, for example, by querying the value of `#DLG$PARENT.CLIENT-DATA`.

## Passing Parameters to the Dialog

It is possible to pass parameters to the dialog receiving the user event.

As operand3 you specify the parameters which are passed to the dialog.

With the PARAMETERS-clause, parameters may be passed selectively.

#### PARAMETERS-clause

`PARAMETERS` [parameter-name = operand3]_ `END-PARAMETERS`

Note
You may only use the PARAMETERS-clause if the target dialog is cataloged.

Dialog-name is the name of the dialog receiving the user-defined event.

When you use only operand3 to pass parameters, it might look like this:

    /* The following parameters are defined in the dialog's
    /* parameter data area:
    1 #DLG-PARM1 (A10)
    1 #DLG-PARM2 (A10)
    1 #DLG-PARM3 (A10)
    1 #DLG-PARM4 (A10)
    /* When sending the user-defined event, pass the operands #MYPARM1 'MYPARM2' to
    the parameters #DLG-PARM1 and #DLG-PARM2:
    SEND EVENT 'MYEVENT' TO #DLG$DIA-ID WITH #MYPARM1 'MYPARM2'

When you use the PARAMETERS-clause, the user-defined event might look like this:

    /* The following parameters are defined in the dialog's
    /* parameter data area:
    1 #DLG-PARM1 (A10)
    1 #DLG-PARM2 (A10)
    1 #DLG-PARM3 (A10)
    1 #DLG-PARM4 (A10)
    /* When sending the user-defined event, the operand #MYPARM2 is passed to the
    /* parameter #DLG-PARM2 and the operand 'MYPARM3' is passed to the parameter
    /* #DLG-PARM3:
    SEND EVENT 'MYEVENT' TO #DLG$DIA-ID
      USING DIALOG 'MYDIALOG'
      WITH PARAMETERS
        #DLG-PARM3='MYPARM3'
        #DLG-PARM2=#MYPARM2
      END-PARAMETERS

To avoid format/length conflicts between operands passed and their parameter definitions, see the `BY VALUE` option of the `DEFINE DATA` statement in the Statements documentation.

### On this page

- About User-Defined Events
- Passing Parameters to the Dialog