Trigger (PRE-QUERY), set dynamically properties....

Introduction

A form trigger is a block of PL/SQL code that adds functionality to your application. Triggers are attached to objects in your application. When a trigger is fired, it execute the code it contains. Each trigger's name defines what event will fire it, for instance, a WHEN-BUTTON-PRESSED trigger executes it's code each time click on the button which trigger is attached, or we can say , a form trigger is a set of PL/SQL actions that happen each time an event such as WHEN-CHECKBOX-CHANGED, WHEN-BUTTON-PRESSED, or WHEN-NEW-RECORD-INSTANCE occurs. You can attach several triggers to data QUERY. The most populer of them are PRE-QUERY and POST-QUERY. 

PRE-QUERY Trigger

The PRE-QUERY trigger fires before SELECT statement finalized.The POST-QUERY trigger fires before selected records are presented to the user. It fires after records are retrieved but before they are displayed. So you can use it to enhance a query's in a number of ways. Your POST-QUERY trigger can contain code to calculate or populate control items.

Change an OBJECT PROPERTY DYNAMICALLY

 You can always change object property dynamically. The SET_OBJECTNAME_PROPERTY built_in sub program will change an object property dynamically.