Emacs/docs/latest/emacs/GTK-Widget-Names

From Get docs

D.5.2 GTK+ widget names

A GTK+ widget is specified by a widget name and a widget class. The widget name refers to a specific widget (e.g., ‘emacs-menuitem’), while the widget class refers to a collection of similar widgets (e.g., ‘GtkMenuItem’). A widget always has a class, but need not have a name.

Absolute names are sequences of widget names or widget classes, corresponding to hierarchies of widgets embedded within other widgets. For example, if a GtkWindow named top contains a GtkVBox named box, which in turn contains a GtkMenuBar called menubar, the absolute class name of the menu-bar widget is GtkWindow.GtkVBox.GtkMenuBar, and its absolute widget name is top.box.menubar.

GTK+ resource files can contain two types of commands for specifying widget appearances:

widget
specifies a style for widgets based on the class name, or just the class.
widget_class
specifies a style for widgets based on the class name.

See the previous subsection for examples of using the widget command; the widget_class command is used similarly. Note that the widget name/class and the style must be enclosed in double-quotes, and these commands must be at the top level in the GTK+ resource file.

As previously noted, you may specify a widget name or class with shell wildcard syntax: ‘*’ matches zero or more characters and ‘?’ matches one character. This example assigns a style to all widgets:

widget "*" style "my_style"