Installing a key binding

A resource file binding consists of a 'binding' definition and a match statement to apply the binding to specific widget types. Details on the matching mechanism are described under Pathnames and patterns. Inside the binding definition, key combinations are bound to specific signal emissions on the target widget. Key combinations are strings consisting of an optional GdkModifierType name and key names such as those defined in <gdk/gdkkeysyms.h> or returned from gdk_keyval_name(), they have to be parsable by gtk_accelerator_parse(). Specifications of signal emissions consist of a string identifying the signal name, and a list of signal specific arguments in parenthesis. For example for binding Control and the left or right cursor keys of a GtkEntry widget to the GtkEntry::move-cursor signal, so movement occurs in 3 letter steps, the following binding can be used:

binding "MoveCursor3" {
  bind "<Control>Right" {
    "move-cursor" (visual-positions, 3, 0)
  }
  bind "<Control>Left" {
    "move-cursor" (visual-positions, -3, 0)
  }
}
class "GtkEntry" binding "MoveCursor3"

Unbinding existing key bindings

Gtk+ already defines a number of useful bindings for the widgets it provides. Because custom bindings set up in RC files take precedence over the default bindings shipped with Gtk+, overriding existing bindings as demonstrated in Installing a key binding works as expected. The same mechanism can not be used to "unbind" existing bindings, however.

binding "MoveCursor3" {
  bind "<Control>Right" { }
  bind "<Control>Left" { }
}
class "GtkEntry" binding "MoveCursor3"

The above example will not have the desired effect of causing "<Control>Right" and "<Control>Left" key presses to be ignored by Gtk+. Instead, it just causes any existing bindings from the bindings set "MoveCursor3" to be deleted, so when "<Control>Right" or "<Control>Left" are pressed, no binding for these keys is found in binding set "MoveCursor3". Gtk+ will thus continue to search for matching key bindings, and will eventually lookup and find the default Gtk+ bindings for entries which implement word movement. To keep Gtk+ from activating its default bindings, the "unbind" keyword can be used like this:

binding "MoveCursor3" {
  unbind "<Control>Right"
  unbind "<Control>Left"
}
class "GtkEntry" binding "MoveCursor3"

Now, Gtk+ will find a match when looking up "<Control>Right" and "<Control>Left" key presses before it resorts to its default bindings, and the match instructs it to abort ("unbind") the search, so the key presses are not consumed by this widget. As usual, further processing of the key presses, e.g. by an entries parent widget, is now possible.

GtkBindingSet

typedef struct {
  gchar			*set_name;
  gint			 priority;
  GSList		*widget_path_pspecs;
  GSList		*widget_class_pspecs;
  GSList		*class_branch_pspecs;
  GtkBindingEntry	*entries;
  GtkBindingEntry	*current;
  guint                  parsed : 1; /* From RC content */
} GtkBindingSet;

A binding set maintains a list of activatable key bindings. A single binding set can match multiple types of widgets. Similar to styles, widgets can be mapped by widget name paths, widget class paths or widget class types. When a binding within a set is matched upon activation, an action signal is emitted on the target widget to carry out the actual activation.

GtkBindingEntry

typedef struct {
  /* key portion
   */
  guint			 keyval;
  GdkModifierType	 modifiers;
  
  GtkBindingSet		*binding_set;
  guint			destroyed : 1;
  guint			in_emission : 1;
  guint                 marks_unbound : 1;
  GtkBindingEntry	*set_next;
  GtkBindingEntry	*hash_next;
  GtkBindingSignal	*signals;
} GtkBindingEntry;

Each key binding element of a binding sets binding list is represented by a GtkBindingEntry.

GtkBindingSignal

typedef struct {
  GtkBindingSignal	*next;
  gchar 		*signal_name;
  guint			 n_args;
  GtkBindingArg		*args;
} GtkBindingSignal;

A GtkBindingSignal stores the necessary information to activate a widget in response to a key press via a signal emission.

GtkBindingArg

typedef struct {
  GType		 arg_type;
  union {
    glong	 long_data;
    gdouble	 double_data;
    gchar	*string_data;
  } d;
} GtkBindingArg;

A GtkBindingArg holds the data associated with an argument for a key binding signal emission as stored in GtkBindingSignal.

gtk_binding_set_new ()

GtkBindingSet* gtk_binding_set_new          (const gchar *set_name);

Gtk+ maintains a global list of binding sets. Each binding set has a unique name which needs to be specified upon creation.

gtk_binding_set_by_class ()

GtkBindingSet* gtk_binding_set_by_class     (gpointer object_class);

This function returns the binding set named after the type name of the passed in class structure. New binding sets are created on demand by this function.

gtk_binding_set_find ()

GtkBindingSet* gtk_binding_set_find         (const gchar *set_name);

Find a binding set by its globally unique name. The set_name can either be a name used for gtk_binding_set_new() or the type name of a class used in gtk_binding_set_by_class().

gtk_bindings_activate ()

gboolean    gtk_bindings_activate           (GtkObject *object,
                                             guint keyval,
                                             GdkModifierType modifiers);

Find a key binding matching keyval and modifiers and activate the binding on object.

gtk_bindings_activate_event ()

gboolean    gtk_bindings_activate_event     (GtkObject *object,
                                             GdkEventKey *event);

Looks up key bindings for object to find one matching event, and if one was found, activate it.

gtk_binding_set_activate ()

gboolean    gtk_binding_set_activate        (GtkBindingSet *binding_set,
                                             guint keyval,
                                             GdkModifierType modifiers,
                                             GtkObject *object);

Find a key binding matching keyval and modifiers within binding_set and activate the binding on object.

gtk_binding_entry_add_signal ()

void        gtk_binding_entry_add_signal    (GtkBindingSet *binding_set,
                                             guint keyval,
                                             GdkModifierType modifiers,
                                             const gchar *signal_name,
                                             guint n_args,
                                             ...);

Override or install a new key binding for keyval with modifiers on binding_set. When the binding is activated, signal_name will be emitted on the target widget, with n_args Varargs used as arguments.

gtk_binding_entry_skip ()

void        gtk_binding_entry_skip          (GtkBindingSet *binding_set,
                                             guint keyval,
                                             GdkModifierType modifiers);

Since 2.12 Install a binding on @binding_set which causes key lookups to be aborted, to prevent bindings from lower priority sets to be activated.

gtk_binding_entry_remove ()

void        gtk_binding_entry_remove        (GtkBindingSet *binding_set,
                                             guint keyval,
                                             GdkModifierType modifiers);

Remove a binding previously installed via gtk_binding_entry_add_signal() on binding_set.

gtk_binding_set_add_path ()

void        gtk_binding_set_add_path        (GtkBindingSet *binding_set,
                                             GtkPathType path_type,
                                             const gchar *path_pattern,
                                             GtkPathPriorityType priority);

This function is used internally by the GtkRC parsing mechanism to assign match patterns to GtkBindingSet structures.