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**REGISTER(** //event//,// handler//,// object// [,//window//] [,//control//] **)**

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| **REGISTER** | Registers an event handling procedure. |
| //event// | An integer constant, variable, expression, or EQUATE containing an event number. A value in the range 400h to 0FFFh is a User-defined event. |
| //handler// | A LONG variable, or expression containing the return value from ADDRESS for the PROCEDURE to handle the //event//. |
| //object// | A LONG integer constant, variable, or expression containing any 32-bit unique value to identify the specific //handler//. This is generally the return value of ADDRESS(SELF) when the //handler// is a CLASS method. |
| //window// | The label of the WINDOW or REPORT whose //event// to handle. If omitted, the current target WINDOW or REPORT is assumed. |
| //control// | An integer constant, EQUATE, variable, or expression containing the field number of the specific control whose //event// to handle. If omitted, the //event// is handled for every control on the //window//. |

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Can also be prototyped as **REGISTEREVENT**.

**REGISTER** registers an event //handler// PROCEDURE called internally by the currently active ACCEPT loop of the specified //window// whenever the specified //event// occurs. This may be a User-defined event, or any other event. User-defined event numbers can be defined as any integer between 400h and 0FFFh.

You may REGISTER multiple //handlers// for the same //event //if you choose--the //handlers// are called by ACCEPT in reverse order of their registration (the last one registered executes first). You may explicitly call UNREGISTER to remove the registration of any specific //handler//. The Clarion runtime library automatically unregisters all registered //event handlers //(for the WINDOW passed as the 4th parameter) as a part of the window's closing (when the outer most ACCEPT loop that is running in the window terminates its execution), so explicitly calling UNREGISTER is not required unless your program's logic requires it.

Anytime the //event// occurs, the //handler// procedure is called internally by the events processor running from within the ACCEPT statement. The value returned by the //handler// determines whether or not ACCEPT cycles for any additional //event// processing.

The handler procedure MUST have 1 parameter: when the //handler// is called the runtime library is passing the //object// value (the 3rd parameter in the call to REGISTER) as its parameter.

The //handler// PROCEDURE must not take any parameters and must return a BYTE containing one of the following EQUATEd values (these EQUATEs are defined in the ABERROR.INC file):

| Level:Benign | Calls any other //handlers// and the ACCEPT loop, if available. |
| Level:Notify | Doesn't call other //handlers// or the ACCEPT loop. This is like executing CYCLE when processing the event in an ACCEPT loop. |
| Level:Fatal | Doesn't call other //handlers// or the ACCEPT loop. This is like executing BREAK when processing the event in an ACCEPT loop. |

**Example:**

**WindowResizeClass.Init PROCEDURE**

** CODE**

** ****REGISTER****(EVENT:Sized,ADDRESS(SELF.TakeResize),ADDRESS(SELF))**

** !Other code follows**

**WindowResizeClass.TakeResize PROCEDURE**

**ReturnValue  BYTE**

** CODE**

** ReturnValue  = Level:Benign**

** RETURN(ReturnValue)**

**See Also:**

[[unregister  unregister event handler .htm|UNREGISTER]]

[[accept  the event processor .htm|ACCEPT]]

[[event  return event number .htm|EVENT]]