On System Event database method

$1 -> On System Event database method

Parameter	Type		Description
$1	Integer	←	Event code

This command is not thread-safe, it cannot be used in preemptive code.

Description

The On System Event database method is called each time a system event occurs. This concerns all 4D environments: 4D (all modes) and 4D Server, as well as 4D applications that are compiled and merged with 4D Volume Desktop.

To process an event, you must test the value of the $1 parameter within the method and compare it to one of the following constants, found in the Database Events theme:

Constant	Type	Value	Comment
On application background move	Integer	1	The 4D application moves to the background
On application foreground move	Integer	2	The 4D application moves to the foreground

These events are generated when a 4D application changes level, irrespective of the user action initiating this change. For example:

• Clicking the window of the application or of another application,
• selecting it using the Alt+Tab (Windows) or Command+Tab (Mac OS) keyboard shortcut,
• Selecting the Hide command in the dock (Mac OS),
• Clicking the application icon in the dock or task bar,
• Clicking the minimize button of the main window (Windows).

It is absolutely necessary to declare the $1 parameter (longint) in the database method. The structure of the database method code is therefore:

  // On System Event database method
 
 var $1 : Integer
 Case of
    :($1=On application background move)
  //Do something
    :($1=On application foreground move)
  //Do something else
 End case