Interactive UI

The 2D canvas in Tizen (the Evas object) has been designed to draw scenes optimally. This means that when drawing a new frame, it does not always read the Evas_Object data. This mechanism can cause a problem for a 3D scene, because the 3D scene is updated by the external module, such as the GPU, and Evas does not know whether the 3D scene is updated.

To solve the problem, GLView provides the elm_glview_changed_set() function to notify Evas that the 3D scene must be updated in the next frame. The draw_glview() callback is then invoked while Evas renders the next frame. The application must call the elm_glview_changed_set() function whenever necessary:

  • Touch Event Handling updates the scene by touch event, and you have to invoke the elm_glview_changed_set() function.
  • Automatic Update must be enabled to be used, and also requires calling the elm_glview_changed_set() function.

Touch Event Handling

To handle touch events in Tizen, you must connect the event callback functions with Evas_object. The functions are registered by the evas_object_event_callback_add() function for a set of specific events which are already defined in EFL. To learn more about EFL event handling, see the Event Handling.

The following examples show how to register callback functions for handling touch information and rotating a cube object:

  1. Registering callback functions

    The following code shows how to add callback functions to Evas_object. The parameters, EVAS_CALLBACK_MOUSE_DOWN, EVAS_CALLBACK_MOUSE_UP, and EVAS_CALLBACK_MOUSE_MOVE, represent the specific events for which callbacks must be called. These events are defined in Evas_Callback_Type.

    static Evas_Object*
    add_glview(Evas_Object *parent, appdata_s *ad)
        Evas_Object *glview;
        /* Create and initialize GLView */
        glview = elm_glview_add(parent);
        /* Initialize elm_GLView and set the rendering callback functions */
        evas_object_event_callback_add(glview, EVAS_CALLBACK_MOUSE_DOWN, mouse_down_cb, ad);
        evas_object_event_callback_add(glview, EVAS_CALLBACK_MOUSE_UP, mouse_up_cb, ad);
        evas_object_event_callback_add(glview, EVAS_CALLBACK_MOUSE_MOVE, mouse_move_cb, ad);
  2. Handling touch events in callback functions

    The following code shows how to define the registered callback functions:

    static void
    mouse_down_cb(void *data, Evas *e, Evas_Object *obj, void *event_info)
        appdata_s *ad = (appdata_s *)data;
        ad->mouse_down = EINA_TRUE;
    static void
    mouse_move_cb(void *data, Evas *e, Evas_Object *obj, void *event_info)
        Evas_Event_Mouse_Move *ev;
        ev = (Evas_Event_Mouse_Move *)event_info;
        appdata_s *ad = (appdata_s *)data;
        float dx = 0, dy = 0;
        if (ad->mouse_down) {
            dx = ev->cur.canvas.x - ev->prev.canvas.x;
            dy = ev->cur.canvas.y - ev->prev.canvas.y;
            ad->xangle += dy;
            ad->yangle += dx;
    static void
    mouse_up_cb(void *data, Evas *e, Evas_Object *obj, void *event_info)
        appdata_s *ad = (appdata_s *)data;
        ad->mouse_down = EINA_FALSE;

    Each callback function has the void *event_info parameter in their signature. However, the parameter works differently depending on the registered events. In the mouse_move_cb() function, the void pointer event_info is cast to the Evas_Event_Mouse_Move type, which is associated with EVAS_CALLBACK_MOUSE_MOVE. Therefore, you can get the information about the screen point when the user touches the screen. Using this information, the angles, xangle and yangle, are accumulated and the accumulated data are used for calculating the rotation matrix in the draw_glview() callback functions.

    Notice the elm_glview_changed_set() function. It notifies EFL that there has been a change in GLView. Then, the main loop of EFL invokes the rendering callback functions in GLView.

Automatic Update

In order to allow GLView to update scenes continuously, you must trigger the GLView rendering at every frame. The Ecore_Animator represents a method to enable the automatic update. It invokes the registered callback at every N seconds where N is the frametime interval set by the ecore_animator_frametime_set() function. Then you can call the elm_glview_changed_set() function at the animator’s callback to keep the 3D scene being rendered while the animator works.

The Ecore_Animator instance can be replaced by Ecore_Timer, which produces the same result as Ecore_Animator. However, since Ecore_Animator provides more advantages in maintaining the update loop, preferably use Ecore_Animator instead of Ecore_Timer. For more information, see the Ecore Animator API (in mobile and wearable applications).

The following example adds and deletes an animator with the callback function:

  1. Adding Ecore_Animator

       Add an animator so that the app regularly
       triggers updates of the GLView using elm_glview_changed_set()
       NOTE: If you delete OpenGL ES, the animator keeps running trying to access it
       To prevent this, delete the animator with ecore_animator_del()
    Ecore_Animator *ani = ecore_animator_add(anim_cb, glview);
    evas_object_data_set(glview, "ani", ani);
    evas_object_event_callback_add(glview, EVAS_CALLBACK_DEL, del_anim_cb, ad);
  2. Setting up callback functions

    static void
    del_anim_cb(void *data, Evas *evas, Evas_Object *obj, void *event_info)
        Ecore_Animator *ani = (Ecore_Animator *)evas_object_data_get(obj, "ani");
    static Eina_Bool
    anim_cb(void *data)
        elm_glview_changed_set((Evas_Object *)data);
        return EINA_TRUE;

    The animator callback function is also triggered when the display is off. Use the ecore_animator_freeze() and ecore_animator_thaw() functions in the app_pause_cb() and app_resume_cb() callbacks for power saving.

Integrating 3D Scene and 2D UI Components

GLView can be used together with Elementary UI components. The following example creates a GLView and Elementary button component together in a simple box container. It is also possible to support interactions between 2D components and 3D scene.

/* Create the box */
Evas_Object *box = elm_box_add(parent);

/* Set the box to vertical */
elm_box_horizontal_set(box, EINA_FALSE);
/* Box expands when its contents need more space */
evas_object_size_hint_weight_set(box, EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);
/* Box fills the available space */
evas_object_size_hint_align_set(box, EVAS_HINT_FILL, EVAS_HINT_FILL);

/* Add glview to the box container */
ad->glview = add_glview(box, ad);
elm_box_pack_end(box, ad->glview);

/* Add button to the box container */
Evas_Object *button = elm_button_add(box);
evas_object_size_hint_weight_set(button, EVAS_HINT_EXPAND, EVAS_HINT_FILL);
evas_object_size_hint_align_set(button, EVAS_HINT_FILL, 1);
elm_object_text_set(button, "Reset Animation");
evas_object_smart_callback_add(button, "clicked", clicked_cb, ad);
elm_box_pack_end(box, button);

static void
clicked_cb(void *user_data, Evas_Object *obj, void *event_info)
    appdata_s *ad = (appdata_s *)user_data;

       It is possible to change the 3D scene
       For example, start animator to rotate the cube
    if (!ad->reset_anim) {
        ad->reset_anim = EINA_TRUE;

        /* Setting animation angle for 0.75 seconds */
        ad->tic_xangle = (ad->xangle - 45.0f) / 45.0f;
        ad->tic_yangle = (ad->yangle - 45.0f) / 45.0f;

           Add animator which calls elm_glview_changed_set() per frame
           This rotates the object tic_x(y)angle along X(Y) axis
           until object reaches the initial angle
        ad->ani = ecore_animator_add(anim_cb, ad);
        evas_object_event_callback_add(ad->glview, EVAS_CALLBACK_DEL, del_anim, ad);
  • Dependencies
    • Tizen 2.4 and Higher for Mobile
    • Tizen 2.3.1 and Higher for Wearable