The applications do not normally grab hardware key events, because each key event is delivered to the focused window by default. Some applications, however, have more advanced functionalities and behavior. For example, in most applications, a volume key press opens a volume control popup. But, in a memo application, you can use the volume key to resize the text.

To receive special hardware key events in the application, use the eext_win_keygrab_set() and eext_win_keygrab_unset() functions.

To grab hardware key events:

1. To use the functions and data types of the EFL Extension API (in mobile and wearable applications), include the <efl_extension.h> header file in your application:

   #include <efl_extension.h>
   

2. Create the application window and add UI components to it, as needed.

   For more information, see Building UI Layouts.

   static void
   create_base_gui(appdata_s *ad)
   {
       Evas_Object *win = NULL;
   
       /* Create the window */
       win = elm_win_util_standard_add(NULL, "extension sample");
       evas_object_smart_callback_add(win, "delete,request", _win_del, NULL);
   
       /* Create UI containers and components */
   
       /* Show the window */
       evas_object_show(win);
   }
   

3. Register and define key event callbacks for the window using the Ecore events:

   Eina_Bool ctrl_pressed = EINA_FALSE;
   
   /* Define the callback */
   static Eina_Bool
   _key_down_cb(void *data __UNUSED__, int type __UNUSED__, void *ev)
   {
       /* Access the fields of the event key type ("*ev") */
       Ecore_Event_Key *event = ev;
   
       /* Test whether the pressed key is Ctrl */
       if (!strcmp("Control_L", event->key)) {
           /* If it is, store that information */
           ctrl_pressed = EINA_TRUE;
       }
   
       /* Let the event continue to other callbacks */
       return ECORE_CALLBACK_PASS_ON;
   }
   
   /* Register the callback */
   ecore_event_handler_add(ECORE_EVENT_KEY_DOWN, _key_down_cb, NULL);
   

4. Grab key events using the eext_win_keygrab_set() function with the application window object and the key string as parameters.

   eext_win_keygrab_set(win, "XF86AudioRaiseVolume");
   

5. When the application no longer needs to grab key events, call the eext_win_keygrab_unset() function:

   eext_win_keygrab_unset(win, "XF86AudioRaiseVolume");
   

The following table lists the hardware keys from which you can grab events in different profiles.

Table: Supported hardware keys