[framework/uifw/elementary.git] / src / lib / elm_theme.h

   /**
    * @defgroup Theme Theme
    *
    * Elementary uses Edje to theme its widgets, naturally. But for the most
    * part this is hidden behind a simpler interface that lets the user set
    * extensions and choose the style of widgets in a much easier way.
    *
    * Instead of thinking in terms of paths to Edje files and their groups
    * each time you want to change the appearance of a widget, Elementary
    * works so you can add any theme file with extensions or replace the
    * main theme at one point in the application, and then just set the style
    * of widgets with elm_object_style_set() and related functions. Elementary
    * will then look in its list of themes for a matching group and apply it,
    * and when the theme changes midway through the application, all widgets
    * will be updated accordingly.
    *
    * There are three concepts you need to know to understand how Elementary
    * theming works: default theme, extensions and overlays.
    *
    * Default theme, obviously enough, is the one that provides the default
    * look of all widgets. End users can change the theme used by Elementary
    * by setting the @c ELM_THEME environment variable before running an
    * application, or globally for all programs using the @c elementary_config
    * utility. Applications can change the default theme using elm_theme_set(),
    * but this can go against the user wishes, so it's not an adviced practice.
    *
    * Ideally, applications should find everything they need in the already
    * provided theme, but there may be occasions when that's not enough and
    * custom styles are required to correctly express the idea. For this
    * cases, Elementary has extensions.
    *
    * Extensions allow the application developer to write styles of its own
    * to apply to some widgets. This requires knowledge of how each widget
    * is themed, as extensions will always replace the entire group used by
    * the widget, so important signals and parts need to be there for the
    * object to behave properly (see documentation of Edje for details).
    * Once the theme for the extension is done, the application needs to add
    * it to the list of themes Elementary will look into, using
    * elm_theme_extension_add(), and set the style of the desired widgets as
    * he would normally with elm_object_style_set().
    *
    * Overlays, on the other hand, can replace the look of all widgets by
    * overriding the default style. Like extensions, it's up to the application
    * developer to write the theme for the widgets it wants, the difference
    * being that when looking for the theme, Elementary will check first the
    * list of overlays, then the set theme and lastly the list of extensions,
    * so with overlays it's possible to replace the default view and every
    * widget will be affected. This is very much alike to setting the whole
    * theme for the application and will probably clash with the end user
    * options, not to mention the risk of ending up with not matching styles
    * across the program. Unless there's a very special reason to use them,
    * overlays should be avoided for the resons exposed before.
    *
    * All these theme lists are handled by ::Elm_Theme instances. Elementary
    * keeps one default internally and every function that receives one of
    * these can be called with NULL to refer to this default (except for
    * elm_theme_free()). It's possible to create a new instance of a
    * ::Elm_Theme to set other theme for a specific widget (and all of its
    * children), but this is as discouraged, if not even more so, than using
    * overlays. Don't use this unless you really know what you are doing.
    *
    * But to be less negative about things, you can look at the following
    * examples:
    * @li @ref theme_example_01 "Using extensions"
    * @li @ref theme_example_02 "Using overlays"
    *
    * @{
    */
   /**
    * @typedef Elm_Theme
    *
    * Opaque handler for the list of themes Elementary looks for when
    * rendering widgets.
    *
    * Stay out of this unless you really know what you are doing. For most
    * cases, sticking to the default is all a developer needs.
    */
   typedef struct _Elm_Theme Elm_Theme;

   /**
    * Create a new specific theme
    *
    * This creates an empty specific theme that only uses the default theme. A
    * specific theme has its own private set of extensions and overlays too
    * (which are empty by default). Specific themes do not fall back to themes
    * of parent objects. They are not intended for this use. Use styles, overlays
    * and extensions when needed, but avoid specific themes unless there is no
    * other way (example: you want to have a preview of a new theme you are
    * selecting in a "theme selector" window. The preview is inside a scroller
    * and should display what the theme you selected will look like, but not
    * actually apply it yet. The child of the scroller will have a specific
    * theme set to show this preview before the user decides to apply it to all
    * applications).
    */
   EAPI Elm_Theme       *elm_theme_new(void);

   /**
    * Free a specific theme
    *
    * @param th The theme to free
    *
    * This frees a theme created with elm_theme_new().
    */
   EAPI void             elm_theme_free(Elm_Theme *th);

   /**
    * Copy the theme fom the source to the destination theme
    *
    * @param th The source theme to copy from
    * @param thdst The destination theme to copy data to
    *
    * This makes a one-time static copy of all the theme config, extensions
    * and overlays from @p th to @p thdst. If @p th references a theme, then
    * @p thdst is also set to reference it, with all the theme settings,
    * overlays and extensions that @p th had.
    */
   EAPI void             elm_theme_copy(Elm_Theme *th, Elm_Theme *thdst);

   /**
    * Tell the source theme to reference the ref theme
    *
    * @param th The theme that will do the referencing
    * @param thref The theme that is the reference source
    *
    * This clears @p th to be empty and then sets it to refer to @p thref
    * so @p th acts as an override to @p thref, but where its overrides
    * don't apply, it will fall through to @p thref for configuration.
    */
   EAPI void             elm_theme_ref_set(Elm_Theme *th, Elm_Theme *thref);

   /**
    * Return the theme referred to
    *
    * @param th The theme to get the reference from
    * @return The referenced theme handle
    *
    * This gets the theme set as the reference theme by elm_theme_ref_set().
    * If no theme is set as a reference, NULL is returned.
    */
   EAPI Elm_Theme       *elm_theme_ref_get(Elm_Theme *th);

   /**
    * Return the default theme
    *
    * @return The default theme handle
    *
    * This returns the internal default theme setup handle that all widgets
    * use implicitly unless a specific theme is set. This is also often use
    * as a shorthand of NULL.
    */
   EAPI Elm_Theme       *elm_theme_default_get(void);

   /**
    * Prepends a theme overlay to the list of overlays
    *
    * @param th The theme to add to, or if NULL, the default theme
    * @param item The Edje file path to be used
    *
    * Use this if your application needs to provide some custom overlay theme
    * (An Edje file that replaces some default styles of widgets) where adding
    * new styles, or changing system theme configuration is not possible. Do
    * NOT use this instead of a proper system theme configuration. Use proper
    * configuration files, profiles, environment variables etc. to set a theme
    * so that the theme can be altered by simple confiugration by a user. Using
    * this call to achieve that effect is abusing the API and will create lots
    * of trouble.
    *
    * @see elm_theme_extension_add()
    */
   EAPI void             elm_theme_overlay_add(Elm_Theme *th, const char *item);

   /**
    * Delete a theme overlay from the list of overlays
    *
    * @param th The theme to delete from, or if NULL, the default theme
    * @param item The name of the theme overlay
    *
    * @see elm_theme_overlay_add()
    */
   EAPI void             elm_theme_overlay_del(Elm_Theme *th, const char *item);

   /**
    * Appends a theme extension to the list of extensions.
    *
    * @param th The theme to add to, or if NULL, the default theme
    * @param item The Edje file path to be used
    *
    * This is intended when an application needs more styles of widgets or new
    * widget themes that the default does not provide (or may not provide). The
    * application has "extended" usage by coming up with new custom style names
    * for widgets for specific uses, but as these are not "standard", they are
    * not guaranteed to be provided by a default theme. This means the
    * application is required to provide these extra elements itself in specific
    * Edje files. This call adds one of those Edje files to the theme search
    * path to be search after the default theme. The use of this call is
    * encouraged when default styles do not meet the needs of the application.
    * Use this call instead of elm_theme_overlay_add() for almost all cases.
    *
    * @see elm_object_style_set()
    */
   EAPI void             elm_theme_extension_add(Elm_Theme *th, const char *item);

   /**
    * Deletes a theme extension from the list of extensions.
    *
    * @param th The theme to delete from, or if NULL, the default theme
    * @param item The name of the theme extension
    *
    * @see elm_theme_extension_add()
    */
   EAPI void             elm_theme_extension_del(Elm_Theme *th, const char *item);

   /**
    * Set the theme search order for the given theme
    *
    * @param th The theme to set the search order, or if NULL, the default theme
    * @param theme Theme search string
    *
    * This sets the search string for the theme in path-notation from first
    * theme to search, to last, delimited by the : character. Example:
    *
    * "shiny:/path/to/file.edj:default"
    *
    * See the ELM_THEME environment variable for more information.
    *
    * @see elm_theme_get()
    * @see elm_theme_list_get()
    */
   EAPI void             elm_theme_set(Elm_Theme *th, const char *theme);

   /**
    * Return the theme search order
    *
    * @param th The theme to get the search order, or if NULL, the default theme
    * @return The internal search order path
    *
    * This function returns a colon separated string of theme elements as
    * returned by elm_theme_list_get().
    *
    * @see elm_theme_set()
    * @see elm_theme_list_get()
    */
   EAPI const char      *elm_theme_get(Elm_Theme *th);

   /**
    * Return a list of theme elements to be used in a theme.
    *
    * @param th Theme to get the list of theme elements from.
    * @return The internal list of theme elements
    *
    * This returns the internal list of theme elements (will only be valid as
    * long as the theme is not modified by elm_theme_set() or theme is not
    * freed by elm_theme_free(). This is a list of strings which must not be
    * altered as they are also internal. If @p th is NULL, then the default
    * theme element list is returned.
    *
    * A theme element can consist of a full or relative path to a .edj file,
    * or a name, without extension, for a theme to be searched in the known
    * theme paths for Elemementary.
    *
    * @see elm_theme_set()
    * @see elm_theme_get()
    */
   EAPI const Eina_List *elm_theme_list_get(const Elm_Theme *th);

   /**
    * Return the full patrh for a theme element
    *
    * @param f The theme element name
    * @param in_search_path Pointer to a boolean to indicate if item is in the search path or not
    * @return The full path to the file found.
    *
    * This returns a string you should free with free() on success, NULL on
    * failure. This will search for the given theme element, and if it is a
    * full or relative path element or a simple searchable name. The returned
    * path is the full path to the file, if searched, and the file exists, or it
    * is simply the full path given in the element or a resolved path if
    * relative to home. The @p in_search_path boolean pointed to is set to
    * EINA_TRUE if the file was a searchable file andis in the search path,
    * and EINA_FALSE otherwise.
    */
   EAPI char            *elm_theme_list_item_path_get(const char *f, Eina_Bool *in_search_path);

   /**
    * Flush the current theme.
    *
    * @param th Theme to flush
    *
    * This flushes caches that let elementary know where to find theme elements
    * in the given theme. If @p th is NULL, then the default theme is flushed.
    * Call this function if source theme data has changed in such a way as to
    * make any caches Elementary kept invalid.
    */
   EAPI void             elm_theme_flush(Elm_Theme *th);

   /**
    * This flushes all themes (default and specific ones).
    *
    * This will flush all themes in the current application context, by calling
    * elm_theme_flush() on each of them.
    */
   EAPI void             elm_theme_full_flush(void);

   /**
    * Set the theme for all elementary using applications on the current display
    *
    * @param theme The name of the theme to use. Format same as the ELM_THEME
    * environment variable.
    */
   EAPI void             elm_theme_all_set(const char *theme);

   /**
    * Return a list of theme elements in the theme search path
    *
    * @return A list of strings that are the theme element names.
    *
    * This lists all available theme files in the standard Elementary search path
    * for theme elements, and returns them in alphabetical order as theme
    * element names in a list of strings. Free this with
    * elm_theme_name_available_list_free() when you are done with the list.
    */
   EAPI Eina_List       *elm_theme_name_available_list_new(void);

   /**
    * Free the list returned by elm_theme_name_available_list_new()
    *
    * This frees the list of themes returned by
    * elm_theme_name_available_list_new(). Once freed the list should no longer
    * be used. a new list mys be created.
    */
   EAPI void             elm_theme_name_available_list_free(Eina_List *list);

   /**
    * Set a specific theme to be used for this object and its children
    *
    * @param obj The object to set the theme on
    * @param th The theme to set
    *
    * This sets a specific theme that will be used for the given object and any
    * child objects it has. If @p th is NULL then the theme to be used is
    * cleared and the object will inherit its theme from its parent (which
    * ultimately will use the default theme if no specific themes are set).
    *
    * Use special themes with great care as this will annoy users and make
    * configuration difficult. Avoid any custom themes at all if it can be
    * helped.
    */
   EAPI void             elm_object_theme_set(Evas_Object *obj, Elm_Theme *th) EINA_ARG_NONNULL(1);

   /**
    * Get the specific theme to be used
    *
    * @param obj The object to get the specific theme from
    * @return The specifc theme set.
    *
    * This will return a specific theme set, or NULL if no specific theme is
    * set on that object. It will not return inherited themes from parents, only
    * the specific theme set for that specific object. See elm_object_theme_set()
    * for more information.
    */
   EAPI Elm_Theme       *elm_object_theme_get(const Evas_Object *obj) EINA_ARG_NONNULL(1);

   /**
    * Get a data item from a theme
    *
    * @param th The theme, or NULL for default theme
    * @param key The data key to search with
    * @return The data value, or NULL on failure
    *
    * This function is used to return data items from edc in @p th, an overlay, or an extension.
    * It works the same way as edje_file_data_get() except that the return is stringshared.
    */
   EAPI const char      *elm_theme_data_get(Elm_Theme *th, const char *key) EINA_ARG_NONNULL(2);

   /**
    * @}
    */