|GTK+ Reference Manual|
GtkUIManager is an object that can construct menu and toolbar widgets from an XML description. These widgets are in turn associated to corresponding actions and action groups.
GtkUIManager supports merging of menus and toolbars for applications that have multiple components, each with separate sets of commands. For example, a word processor that can embed images may want to have toolbar buttons for Bold and Italic when the cursor is on a text block, but Crop and Brightness/Contrast buttons when the cursor is on an image. These actions, which change depending on the state of the application, can be merged and de-merged from a GtkUIManager as appropriate.