On System Event database method
$1 -> On System Event database method
| Parameter | Type | Description | |
|---|---|---|---|
| $1 | Longint | ← | 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 | Longint | 1 | The 4D application moves to the background |
| On application foreground move | Longint | 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