Theme - Using overlays

Overlays are like extensions in that you tell Elementary that some other theme contains the styles you need for your program. The difference is that they will be look in first, so they can override the default style of any widget.

There's not much to say about them that hasn't been said in our previous example about extensions, so going quickly through the code we have a function to load or unload the theme, which will be called when we click any button.

#include <Elementary.h>
static void
_btn_clicked_cb(void *data EINA_UNUSED, Evas_Object *obj EINA_UNUSED, void *ev EINA_UNUSED)
{
static int loaded = 1;
if (loaded)
elm_theme_overlay_del(NULL, edj_path);
else
elm_theme_overlay_add(NULL, edj_path);
loaded = 1 - loaded;
}

And the main function, creating the window and adding some buttons to it. We load our theme as an overlay and nothing else. Notice there's no style set for any button there, which means they should be using the default that we override.

EAPI_MAIN int
elm_main(int argc EINA_UNUSED, char **argv EINA_UNUSED)
{
Evas_Object *win, *box, *btn;
#ifdef PACKAGE_DATA_DIR
elm_app_compile_data_dir_set(PACKAGE_DATA_DIR);
#endif
if (ecore_file_exists("./theme_example.edj"))
{
strcpy(edj_path, "./theme_example.edj");
}
else
{
elm_app_info_set(elm_main, "elementary", "examples/theme_example.edj");
snprintf(edj_path, sizeof(edj_path), "%s/examples/theme_example.edj",
}
elm_theme_overlay_add(NULL, edj_path);
win = elm_win_util_standard_add("theme", "Theme example");
box = elm_box_add(win);
evas_object_size_hint_weight_set(box, EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);
btn = elm_button_add(win);
elm_object_text_set(btn, "Button 1");
elm_box_pack_end(box, btn);
evas_object_smart_callback_add(btn, "clicked", _btn_clicked_cb, NULL);
btn = elm_button_add(win);
elm_object_text_set(btn, "Button 2");
elm_box_pack_end(box, btn);
evas_object_smart_callback_add(btn, "clicked", _btn_clicked_cb, NULL);
btn = elm_button_add(win);
elm_object_text_set(btn, "Button 3");
elm_box_pack_end(box, btn);
evas_object_smart_callback_add(btn, "clicked", _btn_clicked_cb, NULL);
btn = elm_button_add(win);
elm_object_text_set(btn, "Button 4");
elm_box_pack_end(box, btn);
evas_object_smart_callback_add(btn, "clicked", _btn_clicked_cb, NULL);
evas_object_resize(win, 300, 320);
return 0;
}

That's pretty much it. The full code is here and the definition of the theme is the same as before, and can be found in here.

ELM_POLICY_QUIT_LAST_WINDOW_CLOSED
quit when the application's last window is closed
Definition: elm_general.h:248
elm_app_compile_data_dir_set
void elm_app_compile_data_dir_set(const char *dir)
Provide information on the fallback application's data directory, on scenarios where they get overrid...
Definition: elm_main.c:528
elm_box_add
EAPI Evas_Object * elm_box_add(Evas_Object *parent)
Add a new box to the parent.
Definition: elm_box.c:366
elm_app_data_dir_get
const char * elm_app_data_dir_get(void)
Get the application's run time data prefix directory, as set by elm_app_info_set() and the way (envir...
Definition: elm_main.c:586
EINA_UNUSED
#define EINA_UNUSED
Definition: eina_types.h:321
elm_button_add
EAPI Evas_Object * elm_button_add(Evas_Object *parent)
Add a new button to the parent's canvas.
Definition: efl_ui_button.c:477
EVAS_HINT_EXPAND
#define EVAS_HINT_EXPAND
Use with evas_object_size_hint_weight_set(), evas_object_size_hint_weight_get(), evas_object_size_hin...
Definition: Evas_Common.h:292
evas_object_smart_callback_add
void evas_object_smart_callback_add(Evas_Object *eo_obj, const char *event, Evas_Smart_Cb func, const void *data)
Add (register) a callback function to the smart event specified by event on the smart object obj.
Definition: evas_object_smart.c:980
Evas_Object
Efl_Canvas_Object Evas_Object
Definition: Evas_Common.h:180
elm_run
void elm_run(void)
Run Elementary's main loop.
Definition: elm_main.c:1385
ELM_MAIN
#define ELM_MAIN()
macro to be used after the elm_main() function
Definition: elm_general.h:528
elm_theme_overlay_del
void elm_theme_overlay_del(Elm_Theme *th, const char *item)
Delete a theme overlay from the list of overlays.
Definition: elm_theme.c:645
elm_app_info_set
void elm_app_info_set(void *mainfunc, const char *dom, const char *checkfile)
Re-locate the application somewhere else after compilation, if the developer wishes for easier distri...
Definition: elm_main.c:496
elm_win_util_standard_add
Evas_Object * elm_win_util_standard_add(const char *name, const char *title)
Adds a window object with standard setup.
Definition: efl_ui_win.c:9199
evas_object_show
void evas_object_show(Evas_Object *eo_obj)
Makes the given Evas object visible.
Definition: evas_object_main.c:1853
EINA_TRUE
#define EINA_TRUE
Definition: eina_types.h:508
ecore_file_exists
Eina_Bool ecore_file_exists(const char *file)
Checks if the given file exists.
Definition: ecore_file.c:165
elm_policy_set
Eina_Bool elm_policy_set(unsigned int policy, int value)
Set a new policy's value (for a given policy group/identifier).
Definition: elm_main.c:1408
elm_theme_overlay_add
void elm_theme_overlay_add(Elm_Theme *th, const char *item)
Prepends a theme overlay to the list of overlays.
Definition: elm_theme.c:637
elm_win_resize_object_add
void elm_win_resize_object_add(Eo *obj, Evas_Object *subobj)
Add subobj as a resize object of window obj.
Definition: efl_ui_win.c:8899
elm_win_autodel_set
void elm_win_autodel_set(Eo *obj, Eina_Bool autodel)
Set the window's autodel state.
Definition: efl_ui_win.c:6146
ELM_POLICY_QUIT
under which circumstances the application should quit automatically.
Definition: elm_general.h:227