# register_key_event_handler<no value>

{{< callout context="note" title="NOTE" icon="outline/bulb" >}}

Deprecated. Use `fsEventsRegisterKeyEventHandler` instead.

{{< /callout >}}

 

The **register\_key\_event\_handler** function registers a key event callback function.

 

##### Syntax

``` wasm
void register_key_event_handler(
    GAUGE_KEY_EVENT_HANDLER  handler,
    PVOID  userdata
    );
```

 

##### Members

<table><thead><tr class="header"><th>Parameters</th><th>Description</th></tr></thead><tbody><tr class="odd"><td><code>handler</code></td><td><p>Specifies the handler function, which should match the following definition:</p><p><code>typedef void (*GAUGE_KEY_EVENT_HANDLER) (ID32 event, UINT32 evdata, PVOID userdata);</code></p></td></tr><tr class="even"><td><code>userdata</code></td><td>Specifies an optional value for use by the gauge developer. This value will be returned to the key event handler function, whenever it is called.</td></tr></tbody></table>

 

##### Return Values

This function does not return a value.

 

##### Example

This example shows how to receive custom numeric events from part animations.

 

Defined in `gauges.h`:

``` wasm
const int EVENT_BUTTON_PUSH = 0x11000; 
```

Code in the gauge handler:

``` wasm
bool g_ButtonState = false;
    void EventHandler(ID32 event, UINT32 evdata, PVOID userdata)
    {
        switch(event)
        {
            case EVENT_BUTTON_PUSH:
                g_ButtonState = !g_ButtonState;
                break;
            default:
                break;
        }
    }
void FSAPI module_init(void)
    {
        if (NULL != Panels)
            {
                ImportTable.PANELSentry.fnptr = (PPANELS)Panels;
                PanelCallbackInit();
            }
        register_key_event_handler((GAUGE_KEY_EVENT_HANDLER)EventHandler, NULL);
    }  
```

 

##### Remarks

Note that `GAUGE_KEY_EVENT_HANDLER` is **deprecated** along with this function and you should instead be using `GAUGE_KEY_EVENT_HANDLER_EX1` along with the `register_key_event_handler_EX1` function.