Description A GtkUIManager constructs a user interface (menus and toolbars) from one or more UI definitions, which reference actions from one or more action groups. UI Definitions The UI definitions are specified in an XML format which can be roughly described by the following DTD. Do not confuse the GtkUIManager UI Definitions described here with the similarly named GtkBuilder UI Definitions. <!ELEMENT ui (menubar|toolbar|popup|accelerator)* > <!ELEMENT menubar (menuitem|separator|placeholder|menu)* > <!ELEMENT menu (menuitem|separator|placeholder|menu)* > <!ELEMENT popup (menuitem|separator|placeholder|menu)* > <!ELEMENT toolbar (toolitem|separator|placeholder)* > <!ELEMENT placeholder (menuitem|toolitem|separator|placeholder|menu)* > <!ELEMENT menuitem EMPTY > <!ELEMENT toolitem (menu?) > <!ELEMENT separator EMPTY > <!ELEMENT accelerator EMPTY > <!ATTLIST menubar name num;IMPLIED action num;IMPLIED > <!ATTLIST toolbar name num;IMPLIED action num;IMPLIED > <!ATTLIST popup name num;IMPLIED action num;IMPLIED accelerators (true|false) num;IMPLIED > <!ATTLIST placeholder name num;IMPLIED action num;IMPLIED > <!ATTLIST separator name num;IMPLIED action num;IMPLIED expand (true|false) num;IMPLIED > <!ATTLIST menu name num;IMPLIED action num;REQUIRED position (top|bot) num;IMPLIED > <!ATTLIST menuitem name num;IMPLIED action num;REQUIRED position (top|bot) num;IMPLIED always-show-image (true|false) num;IMPLIED > <!ATTLIST toolitem name num;IMPLIED action num;REQUIRED position (top|bot) num;IMPLIED > <!ATTLIST accelerator name num;IMPLIED action num;REQUIRED > There are some additional restrictions beyond those specified in the DTD, e.g. every toolitem must have a toolbar in its anchestry and every menuitem must have a menubar or popup in its anchestry. Since a GMarkup parser is used to parse the UI description, it must not only be valid XML, but valid GMarkup. If a name is not specified, it defaults to the action. If an action is not specified either, the element name is used. The name and action attributes must not contain '/' characters after parsing (since that would mess up path lookup) and must be usable as XML attributes when enclosed in doublequotes, thus they must not '"' characters or references to the quot; entity. The constructed widget hierarchy is very similar to the element tree of the XML, with the exception that placeholders are merged into their parents. The correspondence of XML elements to widgets should be almost obvious: menubar a GtkMenuBar toolbar a GtkToolbar popup a toplevel GtkMenu menu a GtkMenu attached to a menuitem menuitem a GtkMenuItem subclass, the exact type depends on the action toolitem a GtkToolItem subclass, the exact type depends on the action. Note that toolitem elements may contain a menu element, but only if their associated action specifies a GtkMenuToolButton as proxy. separator a GtkSeparatorMenuItem or GtkSeparatorToolItem accelerator a keyboard accelerator The "position" attribute determines where a constructed widget is positioned wrt. to its siblings in the partially constructed tree. If it is "top", the widget is prepended, otherwise it is appended. <hr> UI Merging The most remarkable feature of GtkUIManager is that it can overlay a set of menuitems and toolitems over another one, and demerge them later. Merging is done based on the names of the XML elements. Each element is identified by a path which consists of the names of its anchestors, separated by slashes. For example, the menuitem named "Left" in the example above has the path /ui/menubar/JustifyMenu/Left and the toolitem with the same name has path /ui/toolbar1/JustifyToolItems/Left. <hr> Accelerators Every action has an accelerator path. Accelerators are installed together with menuitem proxies, but they can also be explicitly added with <accelerator> elements in the UI definition. This makes it possible to have accelerators for actions even if they have no visible proxies. <hr> Smart Separators The separators created by GtkUIManager are "smart", i.e. they do not show up in the UI unless they end up between two visible menu or tool items. Separators which are located at the very beginning or end of the menu or toolbar containing them, or multiple separators next to each other, are hidden. This is a useful feature, since the merging of UI elements from multiple sources can make it hard or impossible to determine in advance whether a separator will end up in such an unfortunate position. For separators in toolbars, you can set expand="true" to turn them from a small, visible separator to an expanding, invisible one. Toolitems following an expanding separator are effectively right-aligned. <hr> Empty Menus Submenus pose similar problems to separators inconnection with merging. It is impossible to know in advance whether they will end up empty after merging. GtkUIManager offers two ways to treat empty submenus: make them disappear by hiding the menu item they're attached to add an insensitive "Empty" item The behaviour is chosen based on the "hide_if_empty" property of the action to which the submenu is associated. <hr> GtkUIManager as GtkBuildable The GtkUIManager implementation of the GtkBuildable interface accepts GtkActionGroup objects as <child> elements in UI definitions. A GtkUIManager UI definition as described above can be embedded in an GtkUIManager <object> element in a GtkBuilder UI definition. The widgets that are constructed by a GtkUIManager can be embedded in other parts of the constructed user interface with the help of the "constructor" attribute. See the example below.