Event handler procedures in form modules
In addition to variable declarations and the main program, a form module can contain procedures that are handlers of the events related to the form. The events of opening and closing the form window are the most common events that can be handled in the form module (listing 5.18).
Listing 5.18. Form module
&AtServer Procedure OnCreateAtServer(Cancel, StandardProcessing) // Insert handler content EndProcedure &AtClient Procedure OnOpen(Cancel) // Insert handler content EndProcedure
It is important that the names of these procedures are not fixed, you can name them as you like. And it is not sufficient, for example, to define the OnCreateAtServer or OnOpen procedures in the module. You also have to link them to the respective form events in Designer (fig. 5.17).
Fig. 5.17. Form events
Novice developers often forget about this aspect. To avoid such situations, we recommend that you use the opening buttons in the property palette to generate the procedures (fig. 5.18).
Fig. 5.18. Form events
Alternatively, you can select them from the drop-down list that is available when you are in the form module (fig. 5.19).
Fig. 5.19. List of form events
In this case the procedure definitions are automatically generated and linked to the respective form properties.