GtkIconTheme

GtkIconTheme — Looking up icons by name

Synopsis


#include <gtk/gtk.h>

                    GtkIconInfo;
                    GtkIconTheme;
enum                GtkIconLookupFlags;
#define             GTK_ICON_THEME_ERROR
enum                GtkIconThemeError;
GtkIconTheme*       gtk_icon_theme_new                  (void);
GtkIconTheme*       gtk_icon_theme_get_default          (void);
GtkIconTheme*       gtk_icon_theme_get_for_screen       (GdkScreen *screen);
void                gtk_icon_theme_set_screen           (GtkIconTheme *icon_theme,
                                                         GdkScreen *screen);
void                gtk_icon_theme_set_search_path      (GtkIconTheme *icon_theme,
                                                         const gchar *path[],
                                                         gint n_elements);
void                gtk_icon_theme_get_search_path      (GtkIconTheme *icon_theme,
                                                         gchar **path[],
                                                         gint *n_elements);
void                gtk_icon_theme_append_search_path   (GtkIconTheme *icon_theme,
                                                         const gchar *path);
void                gtk_icon_theme_prepend_search_path  (GtkIconTheme *icon_theme,
                                                         const gchar *path);
void                gtk_icon_theme_set_custom_theme     (GtkIconTheme *icon_theme,
                                                         const gchar *theme_name);
gboolean            gtk_icon_theme_has_icon             (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name);
GtkIconInfo*        gtk_icon_theme_lookup_icon          (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name,
                                                         gint size,
                                                         GtkIconLookupFlags flags);
GtkIconInfo*        gtk_icon_theme_choose_icon          (GtkIconTheme *icon_theme,
                                                         const gchar *icon_names[],
                                                         gint size,
                                                         GtkIconLookupFlags flags);
GdkPixbuf*          gtk_icon_theme_load_icon            (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name,
                                                         gint size,
                                                         GtkIconLookupFlags flags,
                                                         GError **error);
GList*              gtk_icon_theme_list_contexts        (GtkIconTheme *icon_theme);
GList*              gtk_icon_theme_list_icons           (GtkIconTheme *icon_theme,
                                                         const gchar *context);
gint*               gtk_icon_theme_get_icon_sizes       (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name);
char*               gtk_icon_theme_get_example_icon_name
                                                        (GtkIconTheme *icon_theme);
gboolean            gtk_icon_theme_rescan_if_needed     (GtkIconTheme *icon_theme);
void                gtk_icon_theme_add_builtin_icon     (const gchar *icon_name,
                                                         gint size,
                                                         GdkPixbuf *pixbuf);
GtkIconInfo*        gtk_icon_info_copy                  (GtkIconInfo *icon_info);
void                gtk_icon_info_free                  (GtkIconInfo *icon_info);
gint                gtk_icon_info_get_base_size         (GtkIconInfo *icon_info);
const gchar*        gtk_icon_info_get_filename          (GtkIconInfo *icon_info);
GdkPixbuf*          gtk_icon_info_get_builtin_pixbuf    (GtkIconInfo *icon_info);
GdkPixbuf*          gtk_icon_info_load_icon             (GtkIconInfo *icon_info,
                                                         GError **error);
void                gtk_icon_info_set_raw_coordinates   (GtkIconInfo *icon_info,
                                                         gboolean raw_coordinates);
gboolean            gtk_icon_info_get_embedded_rect     (GtkIconInfo *icon_info,
                                                         GdkRectangle *rectangle);
gboolean            gtk_icon_info_get_attach_points     (GtkIconInfo *icon_info,
                                                         GdkPoint **points,
                                                         gint *n_points);
const gchar*        gtk_icon_info_get_display_name      (GtkIconInfo *icon_info);

Object Hierarchy

  GObject
   +----GtkIconTheme

Signals

  "changed"                                        : Run Last

Description

GtkIconTheme provides a facility for looking up icons by name and size. The main reason for using a name rather than simply providing a filename is to allow different icons to be used depending on what icon theme is selecetd by the user. The operation of icon themes on Linux and Unix follows the Icon Theme Specification. There is a default icon theme, named hicolor where applications should install their icons, but more additional application themes can be installed as operating system vendors and users choose.

Named icons are similar to the Themeable Stock Images(3) facility, and the distinction between the two may be a bit confusing. A few things to keep in mind:

  • Stock images usually are used in conjunction with Stock Items(3)., such as GTK_STOCK_OK or GTK_STOCK_OPEN. Named icons are easier to set up and therefore are more useful for new icons that an application wants to add, such as application icons or window icons.

  • Stock images can only be loaded at the symbolic sizes defined by the GtkIconSize enumeration, or by custom sizes defined by gtk_icon_size_register(), while named icons are more flexible and any pixel size can be specified.

  • Because stock images are closely tied to stock items, and thus to actions in the user interface, stock images may come in multiple variants for different widget states or writing directions.

A good rule of thumb is that if there is a stock image for what you want to use, use it, otherwise use a named icon. It turns out that internally stock images are generally defined in terms of one or more named icons. (An example of the more than one case is icons that depend on writing direction; GTK_STOCK_GO_FORWARD uses the two themed icons "gtk-stock-go-forward-ltr" and "gtk-stock-go-forward-rtl".)

In many cases, named themes are used indirectly, via GtkImage or stock items, rather than directly, but looking up icons directly is also simple. The GtkIconTheme object acts as a database of all the icons in the current theme. You can create new GtkIconTheme objects, but its much more efficient to use the standard icon theme for the GdkScreen so that the icon information is shared with other people looking up icons. In the case where the default screen is being used, looking up an icon can be as simple as:

GError *error = NULL;
GtkIconTheme *icon_theme;
GdkPixbuf *pixbuf;

icon_theme = gtk_icon_theme_get_default ();
pixbuf = gtk_icon_theme_load_icon (icon_theme,
                                   "my-icon-name", /* icon name */
                                   48, /* size */
                                   0,  /* flags */
                                   &error);
if (!pixbuf)
  {
    g_warning ("Couldn't load icon: %s", error->message);
    g_error_free (error);
  }
else
  {
    /* Use the pixbuf */
    g_object_unref (pixbuf);
  }

Details

GtkIconInfo

typedef struct _GtkIconInfo GtkIconInfo;

Contains information found when looking up an icon in an icon theme.


GtkIconTheme

typedef struct _GtkIconTheme GtkIconTheme;

Acts as a database of information about an icon theme. Normally, you retrieve the icon theme for a particular screen using gtk_icon_theme_get_for_screen() and it will contain information about current icon theme for that screen, but you can also create a new GtkIconTheme object and set the icon theme name explicitely using gtk_icon_theme_set_custom_theme().


enum GtkIconLookupFlags

typedef enum
{
  GTK_ICON_LOOKUP_NO_SVG = 1 << 0,
  GTK_ICON_LOOKUP_FORCE_SVG = 1 << 1,
  GTK_ICON_LOOKUP_USE_BUILTIN = 1 << 2,
  GTK_ICON_LOOKUP_GENERIC_FALLBACK = 1 << 3
} GtkIconLookupFlags;

Used to specify options for gtk_icon_theme_lookup_icon()

GTK_ICON_LOOKUP_NO_SVG Never return SVG icons, even if gdk-pixbuf supports them. Cannot be used together with GTK_ICON_LOOKUP_FORCE_SVG.
GTK_ICON_LOOKUP_FORCE_SVG Return SVG icons, even if gdk-pixbuf doesn't support them. Cannot be used together with GTK_ICON_LOOKUP_NO_SVG.
GTK_ICON_LOOKUP_USE_BUILTIN When passed to gtk_icon_theme_lookup_icon() includes builtin icons as well as files. For a builtin icon, gtk_icon_info_get_filename() returns NULL and you need to call gtk_icon_info_get_builtin_pixbuf().
GTK_ICON_LOOKUP_GENERIC_FALLBACK Try to shorten icon name at '-' characters before looking at inherited themes. For more general fallback, see gtk_icon_theme_choose_icon(). Since 2.12.

GTK_ICON_THEME_ERROR

#define GTK_ICON_THEME_ERROR gtk_icon_theme_error_quark ()

The GQuark used for GtkIconThemeError errors.


enum GtkIconThemeError

typedef enum {
  GTK_ICON_THEME_NOT_FOUND,
  GTK_ICON_THEME_FAILED
} GtkIconThemeError;

Error codes for GtkIconTheme operations.

GTK_ICON_THEME_NOT_FOUND The icon specified does not exist in the theme
GTK_ICON_THEME_FAILED An unspecified error occurred.

gtk_icon_theme_new ()

GtkIconTheme*       gtk_icon_theme_new                  (void);

Creates a new icon theme object. Icon theme objects are used to lookup up an icon by name in a particular icon theme. Usually, you'll want to use gtk_icon_theme_get_default() or gtk_icon_theme_get_for_screen() rather than creating a new icon theme object for scratch.

Returns : the newly created GtkIconTheme object.

Since 2.4


gtk_icon_theme_get_default ()

GtkIconTheme*       gtk_icon_theme_get_default          (void);

Gets the icon theme for the default screen. See gtk_icon_theme_get_for_screen().

Returns : A unique GtkIconTheme associated with the default screen. This icon theme is associated with the screen and can be used as long as the screen is open. Do not ref or unref it.

Since 2.4


gtk_icon_theme_get_for_screen ()

GtkIconTheme*       gtk_icon_theme_get_for_screen       (GdkScreen *screen);

Gets the icon theme object associated with screen; if this function has not previously been called for the given screen, a new icon theme object will be created and associated with the screen. Icon theme objects are fairly expensive to create, so using this function is usually a better choice than calling than gtk_icon_theme_new() and setting the screen yourself; by using this function a single icon theme object will be shared between users.

screen : a GdkScreen
Returns : A unique GtkIconTheme associated with the given screen. This icon theme is associated with the screen and can be used as long as the screen is open. Do not ref or unref it.

Since 2.4


gtk_icon_theme_set_screen ()

void                gtk_icon_theme_set_screen           (GtkIconTheme *icon_theme,
                                                         GdkScreen *screen);

Sets the screen for an icon theme; the screen is used to track the user's currently configured icon theme, which might be different for different screens.

icon_theme : a GtkIconTheme
screen : a GdkScreen

Since 2.4


gtk_icon_theme_set_search_path ()

void                gtk_icon_theme_set_search_path      (GtkIconTheme *icon_theme,
                                                         const gchar *path[],
                                                         gint n_elements);

Sets the search path for the icon theme object. When looking for an icon theme, GTK+ will search for a subdirectory of one or more of the directories in path with the same name as the icon theme. (Themes from multiple of the path elements are combined to allow themes to be extended by adding icons in the user's home directory.)

In addition if an icon found isn't found either in the current icon theme or the default icon theme, and an image file with the right name is found directly in one of the elements of path, then that image will be used for the icon name. (This is legacy feature, and new icons should be put into the default icon theme, which is called DEFAULT_THEME_NAME, rather than directly on the icon path.)

icon_theme : a GtkIconTheme
path : array of directories that are searched for icon themes
n_elements : number of elements in path.

Since 2.4


gtk_icon_theme_get_search_path ()

void                gtk_icon_theme_get_search_path      (GtkIconTheme *icon_theme,
                                                         gchar **path[],
                                                         gint *n_elements);

Gets the current search path. See gtk_icon_theme_set_search_path().

icon_theme : a GtkIconTheme
path : location to store a list of icon theme path directories or NULL The stored value should be freed with g_strfreev().
n_elements : location to store number of elements in path, or NULL

Since 2.4


gtk_icon_theme_append_search_path ()

void                gtk_icon_theme_append_search_path   (GtkIconTheme *icon_theme,
                                                         const gchar *path);

Appends a directory to the search path. See gtk_icon_theme_set_search_path().

icon_theme : a GtkIconTheme
path : directory name to append to the icon path

Since 2.4


gtk_icon_theme_prepend_search_path ()

void                gtk_icon_theme_prepend_search_path  (GtkIconTheme *icon_theme,
                                                         const gchar *path);

Prepends a directory to the search path. See gtk_icon_theme_set_search_path().

icon_theme : a GtkIconTheme
path : directory name to prepend to the icon path

Since 2.4


gtk_icon_theme_set_custom_theme ()

void                gtk_icon_theme_set_custom_theme     (GtkIconTheme *icon_theme,
                                                         const gchar *theme_name);

Sets the name of the icon theme that the GtkIconTheme object uses overriding system configuration. This function cannot be called on the icon theme objects returned from gtk_icon_theme_get_default() and gtk_icon_theme_get_for_screen().

icon_theme : a GtkIconTheme
theme_name : name of icon theme to use instead of configured theme, or NULL to unset a previously set custom theme

Since 2.4


gtk_icon_theme_has_icon ()

gboolean            gtk_icon_theme_has_icon             (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name);

Checks whether an icon theme includes an icon for a particular name.

icon_theme : a GtkIconTheme
icon_name : the name of an icon
Returns : TRUE if icon_theme includes an icon for icon_name.

Since 2.4


gtk_icon_theme_lookup_icon ()

GtkIconInfo*        gtk_icon_theme_lookup_icon          (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name,
                                                         gint size,
                                                         GtkIconLookupFlags flags);

Looks up a named icon and returns a structure containing information such as the filename of the icon. The icon can then be rendered into a pixbuf using gtk_icon_info_load_icon(). (gtk_icon_theme_load_icon() combines these two steps if all you need is the pixbuf.)

icon_theme : a GtkIconTheme
icon_name : the name of the icon to lookup
size : desired icon size
flags : flags modifying the behavior of the icon lookup
Returns : a GtkIconInfo structure containing information about the icon, or NULL if the icon wasn't found. Free with gtk_icon_info_free()

Since 2.4


gtk_icon_theme_choose_icon ()

GtkIconInfo*        gtk_icon_theme_choose_icon          (GtkIconTheme *icon_theme,
                                                         const gchar *icon_names[],
                                                         gint size,
                                                         GtkIconLookupFlags flags);

Looks up a named icon and returns a structure containing information such as the filename of the icon. The icon can then be rendered into a pixbuf using gtk_icon_info_load_icon(). (gtk_icon_theme_load_icon() combines these two steps if all you need is the pixbuf.)

If icon_names contains more than one name, this function tries them all in the given order before falling back to inherited icon themes.

icon_theme : a GtkIconTheme
icon_names : NULL-terminated array of icon names to lookup
size : desired icon size
flags : flags modifying the behavior of the icon lookup
Returns : a GtkIconInfo structure containing information about the icon, or NULL if the icon wasn't found. Free with gtk_icon_info_free()

Since 2.12


gtk_icon_theme_load_icon ()

GdkPixbuf*          gtk_icon_theme_load_icon            (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name,
                                                         gint size,
                                                         GtkIconLookupFlags flags,
                                                         GError **error);

Looks up an icon in an icon theme, scales it to the given size and renders it into a pixbuf. This is a convenience function; if more details about the icon are needed, use gtk_icon_theme_lookup_icon() followed by gtk_icon_info_load_icon().

Note that you probably want to listen for icon theme changes and update the icon. This is usually done by connecting to the GtkWidget::style-set signal. If for some reason you do not want to update the icon when the icon theme changes, you should consider using gdk_pixbuf_copy() to make a private copy of the pixbuf returned by this function. Otherwise GTK+ may need to keep the old icon theme loaded, which would be a waste of memory.

icon_theme : a GtkIconTheme
icon_name : the name of the icon to lookup
size : the desired icon size. The resulting icon may not be exactly this size; see gtk_icon_info_load_icon().
flags : flags modifying the behavior of the icon lookup
error : Location to store error information on failure, or NULL.
Returns : the rendered icon; this may be a newly created icon or a new reference to an internal icon, so you must not modify the icon. Use g_object_unref() to release your reference to the icon. NULL if the icon isn't found.

Since 2.4


gtk_icon_theme_list_contexts ()

GList*              gtk_icon_theme_list_contexts        (GtkIconTheme *icon_theme);

Gets the list of contexts available within the current hierarchy of icon themes

icon_theme : a GtkIconTheme
Returns : a GList list holding the names of all the contexts in the theme. You must first free each element in the list with g_free(), then free the list itself with g_list_free().

Since 2.12


gtk_icon_theme_list_icons ()

GList*              gtk_icon_theme_list_icons           (GtkIconTheme *icon_theme,
                                                         const gchar *context);

Lists the icons in the current icon theme. Only a subset of the icons can be listed by providing a context string. The set of values for the context string is system dependent, but will typically include such values as "Applications" and "MimeTypes".

icon_theme : a GtkIconTheme
context : a string identifying a particular type of icon, or NULL to list all icons.
Returns : a GList list holding the names of all the icons in the theme. You must first free each element in the list with g_free(), then free the list itself with g_list_free().

Since 2.4


gtk_icon_theme_get_icon_sizes ()

gint*               gtk_icon_theme_get_icon_sizes       (GtkIconTheme *icon_theme,
                                                         const gchar *icon_name);

Returns an array of integers describing the sizes at which the icon is available without scaling. A size of -1 means that the icon is available in a scalable format. The array is zero-terminated.

icon_theme : a GtkIconTheme
icon_name : the name of an icon
Returns : An newly allocated array describing the sizes at which the icon is available. The array should be freed with g_free() when it is no longer needed.

Since 2.6


gtk_icon_theme_get_example_icon_name ()

char*               gtk_icon_theme_get_example_icon_name
                                                        (GtkIconTheme *icon_theme);

Gets the name of an icon that is representative of the current theme (for instance, to use when presenting a list of themes to the user.)

icon_theme : a GtkIconTheme
Returns : the name of an example icon or NULL. Free with g_free().

Since 2.4


gtk_icon_theme_rescan_if_needed ()

gboolean            gtk_icon_theme_rescan_if_needed     (GtkIconTheme *icon_theme);

Checks to see if the icon theme has changed; if it has, any currently cached information is discarded and will be reloaded next time icon_theme is accessed.

icon_theme : a GtkIconTheme
Returns : TRUE if the icon theme has changed and needed to be reloaded.

Since 2.4


gtk_icon_theme_add_builtin_icon ()

void                gtk_icon_theme_add_builtin_icon     (const gchar *icon_name,
                                                         gint size,
                                                         GdkPixbuf *pixbuf);

Registers a built-in icon for icon theme lookups. The idea of built-in icons is to allow an application or library that uses themed icons to function requiring files to be present in the file system. For instance, the default images for all of GTK+'s stock icons are registered as built-icons.

In general, if you use gtk_icon_theme_add_builtin_icon() you should also install the icon in the icon theme, so that the icon is generally available.

This function will generally be used with pixbufs loaded via gdk_pixbuf_new_from_inline().

icon_name : the name of the icon to register
size : the size at which to register the icon (different images can be registered for the same icon name at different sizes.)
pixbuf : GdkPixbuf that contains the image to use for icon_name.

Since 2.4


gtk_icon_info_copy ()

GtkIconInfo*        gtk_icon_info_copy                  (GtkIconInfo *icon_info);

Make a copy of a GtkIconInfo.

icon_info : a GtkIconInfo
Returns : the new GtkIconInfo

Since 2.4


gtk_icon_info_free ()

void                gtk_icon_info_free                  (GtkIconInfo *icon_info);

Free a GtkIconInfo and associated information

icon_info : a GtkIconInfo

Since 2.4


gtk_icon_info_get_base_size ()

gint                gtk_icon_info_get_base_size         (GtkIconInfo *icon_info);

Gets the base size for the icon. The base size is a size for the icon that was specified by the icon theme creator. This may be different than the actual size of image; an example of this is small emblem icons that can be attached to a larger icon. These icons will be given the same base size as the larger icons to which they are attached.

icon_info : a GtkIconInfo
Returns : the base size, or 0, if no base size is known for the icon.

Since 2.4


gtk_icon_info_get_filename ()

const gchar*        gtk_icon_info_get_filename          (GtkIconInfo *icon_info);

Gets the filename for the icon. If the GTK_ICON_LOOKUP_USE_BUILTIN flag was passed to gtk_icon_theme_lookup_icon(), there may be no filename if a builtin icon is returned; in this case, you should use gtk_icon_info_get_builtin_pixbuf().

icon_info : a GtkIconInfo
Returns : the filename for the icon, or NULL if gtk_icon_info_get_builtin_pixbuf() should be used instead. The return value is owned by GTK+ and should not be modified or freed.

Since 2.4


gtk_icon_info_get_builtin_pixbuf ()

GdkPixbuf*          gtk_icon_info_get_builtin_pixbuf    (GtkIconInfo *icon_info);

Gets the built-in image for this icon, if any. To allow GTK+ to use built in icon images, you must pass the GTK_ICON_LOOKUP_USE_BUILTIN to gtk_icon_theme_lookup_icon().

icon_info : a GtkIconInfo structure
Returns : the built-in image pixbuf, or NULL. No extra reference is added to the returned pixbuf, so if you want to keep it around, you must use g_object_ref(). The returned image must not be modified.

Since 2.4


gtk_icon_info_load_icon ()

GdkPixbuf*          gtk_icon_info_load_icon             (GtkIconInfo *icon_info,
                                                         GError **error);

Renders an icon previously looked up in an icon theme using gtk_icon_theme_lookup_icon(); the size will be based on the size passed to gtk_icon_theme_lookup_icon(). Note that the resulting pixbuf may not be exactly this size; an icon theme may have icons that differ slightly from their nominal sizes, and in addition GTK+ will avoid scaling icons that it considers sufficiently close to the requested size or for which the source image would have to be scaled up too far. (This maintains sharpness.)

icon_info : a GtkIconInfo structure from gtk_icon_theme_lookup_icon()
error : location to store error information on failure, or NULL.
Returns : the rendered icon; this may be a newly created icon or a new reference to an internal icon, so you must not modify the icon. Use g_object_unref() to release your reference to the icon.

Since 2.4


gtk_icon_info_set_raw_coordinates ()

void                gtk_icon_info_set_raw_coordinates   (GtkIconInfo *icon_info,
                                                         gboolean raw_coordinates);

Sets whether the coordinates returned by gtk_icon_info_get_embedded_rect() and gtk_icon_info_get_attach_points() should be returned in their original form as specified in the icon theme, instead of scaled appropriately for the pixbuf returned by gtk_icon_info_load_icon().

Raw coordinates are somewhat strange; they are specified to be with respect to the unscaled pixmap for PNG and XPM icons, but for SVG icons, they are in a 1000x1000 coordinate space that is scaled to the final size of the icon. You can determine if the icon is an SVG icon by using gtk_icon_info_get_filename(), and seeing if it is non-NULL and ends in '.svg'.

This function is provided primarily to allow compatibility wrappers for older API's, and is not expected to be useful for applications.

icon_info : a GtkIconInfo
raw_coordinates : whether the coordinates of embedded rectangles and attached points should be returned in their original (unscaled) form.

Since 2.4


gtk_icon_info_get_embedded_rect ()

gboolean            gtk_icon_info_get_embedded_rect     (GtkIconInfo *icon_info,
                                                         GdkRectangle *rectangle);

Gets the coordinates of a rectangle within the icon that can be used for display of information such as a preview of the contents of a text file. See gtk_icon_info_set_raw_coordinates() for further information about the coordinate system.

icon_info : a GtkIconInfo
rectangle : GdkRectangle in which to store embedded rectangle coordinates; coordinates are only stored when this function returns TRUE.
Returns : TRUE if the icon has an embedded rectangle

Since 2.4


gtk_icon_info_get_attach_points ()

gboolean            gtk_icon_info_get_attach_points     (GtkIconInfo *icon_info,
                                                         GdkPoint **points,
                                                         gint *n_points);

Fetches the set of attach points for an icon. An attach point is a location in the icon that can be used as anchor points for attaching emblems or overlays to the icon.

icon_info : a GtkIconInfo
points : location to store pointer to an array of points, or NULL free the array of points with g_free().
n_points : location to store the number of points in points, or NULL
Returns : TRUE if there are any attach points for the icon.

Since 2.4


gtk_icon_info_get_display_name ()

const gchar*        gtk_icon_info_get_display_name      (GtkIconInfo *icon_info);

Gets the display name for an icon. A display name is a string to be used in place of the icon name in a user visible context like a list of icons.

icon_info : a GtkIconInfo
Returns : the display name for the icon or NULL, if the icon doesn't have a specified display name. This value is owned icon_info and must not be modified or free.

Since 2.4

Signal Details

The "changed" signal

void                user_function                      (GtkIconTheme *icon_theme,
                                                        gpointer      user_data)       : Run Last

Emitted when the current icon theme is switched or GTK+ detects that a change has occurred in the contents of the current icon theme.

icon_theme : the icon theme
user_data : user data set when the signal handler was connected.