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4D v14.3

On System Event database method


$1 -> On System Event database method

Parameter	Type	Description
$1	Longint	Event 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 after host database exit	Longint	4	The On Exit database method of the host database has just finished running
On after host database startup	Longint	2	The On Startup database method of the host database just finished running
On application background move	Longint	1	The 4D application moves to the background
On application foreground move	Longint	2	The 4D application moves to the foreground
On before host database exit	Longint	3	The host database is closing. The On Exit database method of the host database has not yet been called. The On Exit database method of the host database is not called while the On Host Database Event database method of the component is running
On before host database startup	Longint	1	The host database has just been started. The On Startup database method method of the host database has not yet been called. The On Startup database method of the host database is not called while the On Host Database Event database method of the component is running

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

 

 C_LONGINT($1)

 Case of

    :($1=On application background move)

  //Do something

    :($1=On application foreground move)

  //Do something else

 End case