Signal Handling

Elementary objects have a communication interface between the application logic (code) and UI (theme). You can emit signals from the code to a theme, or create handles for the signals emitted from themes. Signals are identified by strings.

Using signals in the EDC file is simple:

  1. Create a program that changes the rectangle color between red and blue when specific signals are received. Set the signal name to the signal attribute:

    collections {
   group { name: "main";
      parts {
         part { name: "rect1";
            type: RECT;
            description {
               state: "default" 0.0;
               min: 100 100;
               max: 100 100;
               color: 255 0 0 255;
            }
            description {
               state: "default" 1.0;
               min: 100 100;
               max: 100 100;
               color: 0 0 255 255;
            }
         }
         part { name: "swallow.check";
            type: SWALLOW;
            description {
               state: "default" 0.0;
               align: 0.0 0.0;
               rel1.relative: 0.0 0.0;
               rel2.relative: 0.0 0.0;
            }
         }
      }
      programs {
         program { name: "to_default_0";
            signal: "to,state,default,0";
            action: STATE_SET "default" 0.00;
            transition: ACCELERATE 0.5 CURRENT;
            target: "rect1";
         }
         program { name: "to_default_1";
            signal: "to,state,default,1";
            action: STATE_SET "default" 1.00;
            transition: ACCELERATE 0.5 CURRENT;
            target: "rect1";
         }
      }
   }
}

  2. Emit signals from the C code:

    1. Create a window with the check UI component. Define a callback for when the check component is selected.

      static void
create_base_gui(appdata_s *ad)
{
   char edj_path[PATH_MAX] = {0,};

   /* Create a window */
   ad->win = elm_win_util_standard_add(PACKAGE, PACKAGE);
   elm_win_conformant_set(ad->win, EINA_TRUE);
   elm_win_autodel_set(ad->win, EINA_TRUE);

   if (elm_win_wm_rotation_supported_get(ad->win)) {
      int rots[4] = {0, 90, 180, 270};
      elm_win_wm_rotation_available_rotations_set(ad->win,
                                                  (const int *)(&rots), 4);
   }

   evas_object_smart_callback_add(ad->win, "delete,request",
                                  win_delete_request_cb, NULL);
   eext_object_event_callback_add(ad->win, EEXT_CALLBACK_BACK, win_back_cb, ad);

   /* Create a conformant */
   ad->conform = elm_conformant_add(ad->win);
   elm_win_indicator_mode_set(ad->win, ELM_WIN_INDICATOR_SHOW);
   elm_win_indicator_opacity_set(ad->win, ELM_WIN_INDICATOR_OPAQUE);
   evas_object_size_hint_weight_set(ad->conform, EVAS_HINT_EXPAND,
                                    EVAS_HINT_EXPAND);
   elm_win_resize_object_add(ad->win, ad->conform);
   evas_object_show(ad->conform);

   /* Set a base layout */
   app_get_resource(EDJ_FILE, edj_path, (int)PATH_MAX);
   ad->layout = elm_layout_add(ad->win);
   elm_layout_file_set(ad->layout, edj_path, GRP_MAIN);
   evas_object_size_hint_weight_set(ad->layout, EVAS_HINT_EXPAND,
                                    EVAS_HINT_EXPAND);

   ad->check = elm_check_add(ad->win);
   elm_object_part_content_set(ad->layout, "swallow.check", ad->check);
   evas_object_smart_callback_add(ad->check, "changed", _check_toggled, ad);

   /* Show the window */
   evas_object_show(ad->win);
}

      The following figure displays the result.

      Signal implemented on the screen

    2. The following example implements the callback for the changed event from the check component. When the changed event is triggered, a signal is emitted from the C code to the EDC file.

      static void
_check_toggled(void *data, Evas_Object *obj, void *event_info)
{
   appdata_s *ad = data;

   if (elm_check_state_get(obj))
      elm_object_signal_emit(ad->layout, "to,state,default,1", "");
   else
      elm_object_signal_emit(ad->layout, "to,state,default,0", "");
}

      The following figure displays the result.

      Check component status changed

  • Dependencies
    • Tizen 2.4 and Higher for Mobile
    • Tizen 2.3.1 and Higher for Wearable
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