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Events

Events — Functions for handling events from the window system

Types and Values

Includes

#include <gdk/gdk.h>

Description

This section describes functions dealing with events from the window system.

In GTK+ applications the events are handled automatically in gtk_main_do_event() and passed on to the appropriate widgets, so these functions are rarely needed. Though some of the fields in the Event Structures are useful.

Functions

GDK_PRIORITY_EVENTS

#define             GDK_PRIORITY_EVENTS

This is the priority that events from the X server are given in the GLib Main Loop.


GDK_PRIORITY_REDRAW

#define GDK_PRIORITY_REDRAW     (G_PRIORITY_HIGH_IDLE + 20)

This is the priority that the idle handler processing window updates is given in the GLib Main Loop.


GDK_EVENT_PROPAGATE

#define GDK_EVENT_PROPAGATE     (FALSE)

Use this macro as the return value for continuing the propagation of an event handler.

Since 3.4


GDK_EVENT_STOP

#define GDK_EVENT_STOP          (TRUE)

Use this macro as the return value for stopping the propagation of an event handler.

Since 3.4


GDK_BUTTON_PRIMARY

#define GDK_BUTTON_PRIMARY      (1)

The primary button. This is typically the left mouse button, or the right button in a left-handed setup.

Since 3.4


GDK_BUTTON_MIDDLE

#define GDK_BUTTON_MIDDLE       (2)

The middle button.

Since 3.4


GDK_BUTTON_SECONDARY

#define GDK_BUTTON_SECONDARY    (3)

The secondary button. This is typically the right mouse button, or the left button in a left-handed setup.

Since 3.4


gdk_events_pending ()

gboolean
gdk_events_pending (void);

Checks if any events are ready to be processed for any display.

Returns

TRUE if any events are pending.


gdk_event_peek ()

GdkEvent *
gdk_event_peek (void);

If there is an event waiting in the event queue of some open display, returns a copy of it. See gdk_display_peek_event().

Returns

a copy of the first GdkEvent on some event queue, or NULL if no events are in any queues. The returned GdkEvent should be freed with gdk_event_free().


gdk_event_get ()

GdkEvent *
gdk_event_get (void);

Checks all open displays for a GdkEvent to process,to be processed on, fetching events from the windowing system if necessary. See gdk_display_get_event().

Returns

the next GdkEvent to be processed, or NULL if no events are pending. The returned GdkEvent should be freed with gdk_event_free().


gdk_event_put ()

void
gdk_event_put (const GdkEvent *event);

Appends a copy of the given event onto the front of the event queue for event->any.window’s display, or the default event queue if event->any.window is NULL. See gdk_display_put_event().

Parameters

event

a GdkEvent.

 

gdk_event_new ()

GdkEvent *
gdk_event_new (GdkEventType type);

Creates a new event of the given type. All fields are set to 0.

Parameters

type

a GdkEventType

 

Returns

a newly-allocated GdkEvent. The returned GdkEvent should be freed with gdk_event_free().

Since 2.2


gdk_event_copy ()

GdkEvent *
gdk_event_copy (const GdkEvent *event);

Copies a GdkEvent, copying or incrementing the reference count of the resources associated with it (e.g. GdkWindow’s and strings).

Parameters

event

a GdkEvent

 

Returns

a copy of event . The returned GdkEvent should be freed with gdk_event_free().


gdk_event_free ()

void
gdk_event_free (GdkEvent *event);

Frees a GdkEvent, freeing or decrementing any resources associated with it. Note that this function should only be called with events returned from functions such as gdk_event_peek(), gdk_event_get(), gdk_event_copy() and gdk_event_new().

Parameters

event

a GdkEvent.

 

gdk_event_get_axis ()

gboolean
gdk_event_get_axis (const GdkEvent *event,
                    GdkAxisUse axis_use,
                    gdouble *value);

Extract the axis value for a particular axis use from an event structure.

Parameters

event

a GdkEvent

 

axis_use

the axis use to look for

 

value

location to store the value found.

[out]

Returns

TRUE if the specified axis was found, otherwise FALSE


gdk_event_get_button ()

gboolean
gdk_event_get_button (const GdkEvent *event,
                      guint *button);

Extract the button number from an event.

Parameters

event

a GdkEvent

 

button

location to store mouse button number.

[out]

Returns

TRUE if the event delivered a button number

Since 3.2


gdk_event_get_click_count ()

gboolean
gdk_event_get_click_count (const GdkEvent *event,
                           guint *click_count);

Extracts the click count from an event.

Parameters

event

a GdkEvent

 

click_count

location to store click count.

[out]

Returns

TRUE if the event delivered a click count

Since 3.2


gdk_event_get_coords ()

gboolean
gdk_event_get_coords (const GdkEvent *event,
                      gdouble *x_win,
                      gdouble *y_win);

Extract the event window relative x/y coordinates from an event.

Parameters

event

a GdkEvent

 

x_win

location to put event window x coordinate.

[out]

y_win

location to put event window y coordinate.

[out]

Returns

TRUE if the event delivered event window coordinates


gdk_event_get_keycode ()

gboolean
gdk_event_get_keycode (const GdkEvent *event,
                       guint16 *keycode);

Extracts the hardware keycode from an event.

Parameters

event

a GdkEvent

 

keycode

location to store the keycode.

[out]

Returns

TRUE if the event delivered a hardware keycode

Since 3.2


gdk_event_get_keyval ()

gboolean
gdk_event_get_keyval (const GdkEvent *event,
                      guint *keyval);

Extracts the keyval from an event.

Parameters

event

a GdkEvent

 

keyval

location to store the keyval.

[out]

Returns

TRUE if the event delivered a key symbol

Since 3.2


gdk_event_get_root_coords ()

gboolean
gdk_event_get_root_coords (const GdkEvent *event,
                           gdouble *x_root,
                           gdouble *y_root);

Extract the root window relative x/y coordinates from an event.

Parameters

event

a GdkEvent

 

x_root

location to put root window x coordinate.

[out]

y_root

location to put root window y coordinate.

[out]

Returns

TRUE if the event delivered root window coordinates


gdk_event_get_scroll_direction ()

gboolean
gdk_event_get_scroll_direction (const GdkEvent *event,
                                GdkScrollDirection *direction);

Extracts the scroll direction from an event.

Parameters

event

a GdkEvent

 

direction

location to store the scroll direction.

[out]

Returns

TRUE if the event delivered a scroll direction

Since 3.2


gdk_event_get_scroll_deltas ()

gboolean
gdk_event_get_scroll_deltas (const GdkEvent *event,
                             gdouble *delta_x,
                             gdouble *delta_y);

Retrieves the scroll deltas from a GdkEvent

Parameters

event

a GdkEvent

 

delta_x

return location for X delta.

[out]

delta_y

return location for Y delta.

[out]

Returns

TRUE if the event contains smooth scroll information

Since 3.4


gdk_event_get_state ()

gboolean
gdk_event_get_state (const GdkEvent *event,
                     GdkModifierType *state);

If the event contains a “state” field, puts that field in state . Otherwise stores an empty state (0). Returns TRUE if there was a state field in the event. event may be NULL, in which case it’s treated as if the event had no state field.

Parameters

event

a GdkEvent or NULL

 

state

return location for state.

[out]

Returns

TRUE if there was a state field in the event


gdk_event_get_time ()

guint32
gdk_event_get_time (const GdkEvent *event);

returns GDK_CURRENT_TIME. If event is NULL, returns GDK_CURRENT_TIME.

Parameters

event

a GdkEvent

 

Returns

time stamp field from event


gdk_event_get_window ()

GdkWindow *
gdk_event_get_window (const GdkEvent *event);

Extracts the GdkWindow associated with an event.

Parameters

event

a GdkEvent

 

Returns

The GdkWindow associated with the event.

[transfer none]

Since 3.10


gdk_event_get_event_type ()

GdkEventType
gdk_event_get_event_type (const GdkEvent *event);

Retrieves the type of the event.

Parameters

event

a GdkEvent

 

Returns

a GdkEventType

Since 3.10


gdk_event_get_event_sequence ()

GdkEventSequence *
gdk_event_get_event_sequence (const GdkEvent *event);

If event if of type GDK_TOUCH_BEGIN, GDK_TOUCH_UPDATE, GDK_TOUCH_END or GDK_TOUCH_CANCEL, returns the GdkEventSequence to which the event belongs. Otherwise, return NULL.

Parameters

event

a GdkEvent

 

Returns

the event sequence that the event belongs to

Since 3.4


gdk_event_request_motions ()

void
gdk_event_request_motions (const GdkEventMotion *event);

Request more motion notifies if event is a motion notify hint event.

This function should be used instead of gdk_window_get_pointer() to request further motion notifies, because it also works for extension events where motion notifies are provided for devices other than the core pointer. Coordinate extraction, processing and requesting more motion events from a GDK_MOTION_NOTIFY event usually works like this:

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{
  // motion_event handler
  x = motion_event->x;
  y = motion_event->y;
  // handle (x,y) motion
  gdk_event_request_motions (motion_event); // handles is_hint events
}

Parameters

event

a valid GdkEvent

 

Since 2.12


gdk_events_get_angle ()

gboolean
gdk_events_get_angle (GdkEvent *event1,
                      GdkEvent *event2,
                      gdouble *angle);

If both events contain X/Y information, this function will return TRUE and return in angle the relative angle from event1 to event2 . The rotation direction for positive angles is from the positive X axis towards the positive Y axis.

Parameters

event1

first GdkEvent

 

event2

second GdkEvent

 

angle

return location for the relative angle between both events.

[out]

Returns

TRUE if the angle could be calculated.

Since 3.0


gdk_events_get_center ()

gboolean
gdk_events_get_center (GdkEvent *event1,
                       GdkEvent *event2,
                       gdouble *x,
                       gdouble *y);

If both events contain X/Y information, the center of both coordinates will be returned in x and y .

Parameters

event1

first GdkEvent

 

event2

second GdkEvent

 

x

return location for the X coordinate of the center.

[out]

y

return location for the Y coordinate of the center.

[out]

Returns

TRUE if the center could be calculated.

Since 3.0


gdk_events_get_distance ()

gboolean
gdk_events_get_distance (GdkEvent *event1,
                         GdkEvent *event2,
                         gdouble *distance);

If both events have X/Y information, the distance between both coordinates (as in a straight line going from event1 to event2 ) will be returned.

Parameters

event1

first GdkEvent

 

event2

second GdkEvent

 

distance

return location for the distance.

[out]

Returns

TRUE if the distance could be calculated.

Since 3.0


gdk_event_triggers_context_menu ()

gboolean
gdk_event_triggers_context_menu (const GdkEvent *event);

This function returns whether a GdkEventButton should trigger a context menu, according to platform conventions. The right mouse button always triggers context menus. Additionally, if gdk_keymap_get_modifier_mask() returns a non-0 mask for GDK_MODIFIER_INTENT_CONTEXT_MENU, then the left mouse button will also trigger a context menu if this modifier is pressed.

This function should always be used instead of simply checking for event->button == GDK_BUTTON_SECONDARY.

Parameters

event

a GdkEvent, currently only button events are meaningful values

 

Returns

TRUE if the event should trigger a context menu.

Since 3.4


gdk_event_handler_set ()

void
gdk_event_handler_set (GdkEventFunc func,
                       gpointer data,
                       GDestroyNotify notify);

Sets the function to call to handle all events from GDK.

Note that GTK+ uses this to install its own event handler, so it is usually not useful for GTK+ applications. (Although an application can call this function then call gtk_main_do_event() to pass events to GTK+.)

Parameters

func

the function to call to handle events from GDK.

 

data

user data to pass to the function.

 

notify

the function to call when the handler function is removed, i.e. when gdk_event_handler_set() is called with another event handler.

 

GdkEventFunc ()

void
(*GdkEventFunc) (GdkEvent *event,
                 gpointer data);

Specifies the type of function passed to gdk_event_handler_set() to handle all GDK events.

Parameters

event

the GdkEvent to process.

 

data

user data set when the event handler was installed with gdk_event_handler_set().

[closure]

gdk_get_show_events ()

gboolean
gdk_get_show_events (void);

Gets whether event debugging output is enabled.

Returns

TRUE if event debugging output is enabled.


gdk_set_show_events ()

void
gdk_set_show_events (gboolean show_events);

Sets whether a trace of received events is output. Note that GTK+ must be compiled with debugging (that is, configured using the --enable-debug option) to use this option.

Parameters

show_events

TRUE to output event debugging information.

 

gdk_event_set_screen ()

void
gdk_event_set_screen (GdkEvent *event,
                      GdkScreen *screen);

Sets the screen for event to screen . The event must have been allocated by GTK+, for instance, by gdk_event_copy().

Parameters

event

a GdkEvent

 

screen

a GdkScreen

 

Since 2.2


gdk_event_get_screen ()

GdkScreen *
gdk_event_get_screen (const GdkEvent *event);

Returns the screen for the event. The screen is typically the screen for event->any.window, but for events such as mouse events, it is the screen where the pointer was when the event occurs - that is, the screen which has the root window to which event->motion.x_root and event->motion.y_root are relative.

Parameters

event

a GdkEvent

 

Returns

the screen for the event.

[transfer none]

Since 2.2


gdk_event_get_device ()

GdkDevice *
gdk_event_get_device (const GdkEvent *event);

If the event contains a “device” field, this function will return it, else it will return NULL.

Parameters

event

a GdkEvent.

 

Returns

a GdkDevice, or NULL.

[transfer none]

Since 3.0


gdk_event_set_device ()

void
gdk_event_set_device (GdkEvent *event,
                      GdkDevice *device);

Sets the device for event to device . The event must have been allocated by GTK+, for instance, by gdk_event_copy().

Parameters

event

a GdkEvent

 

device

a GdkDevice

 

Since 3.0


gdk_event_get_source_device ()

GdkDevice *
gdk_event_get_source_device (const GdkEvent *event);

This function returns the hardware (slave) GdkDevice that has triggered the event, falling back to the virtual (master) device (as in gdk_event_get_device()) if the event wasn’t caused by interaction with a hardware device. This may happen for example in synthesized crossing events after a GdkWindow updates its geometry or a grab is acquired/released.

If the event does not contain a device field, this function will return NULL.

Parameters

event

a GdkEvent

 

Returns

a GdkDevice, or NULL.

[transfer none]

Since 3.0


gdk_event_set_source_device ()

void
gdk_event_set_source_device (GdkEvent *event,
                             GdkDevice *device);

Sets the slave device for event to device .

The event must have been allocated by GTK+, for instance by gdk_event_copy().

Parameters

event

a GdkEvent

 

device

a GdkDevice

 

Since 3.0


gdk_setting_get ()

gboolean
gdk_setting_get (const gchar *name,
                 GValue *value);

Obtains a desktop-wide setting, such as the double-click time, for the default screen. See gdk_screen_get_setting().

Parameters

name

the name of the setting.

 

value

location to store the value of the setting.

 

Returns

TRUE if the setting existed and a value was stored in value , FALSE otherwise.

Types and Values

enum GdkEventType

Specifies the type of the event.

Do not confuse these events with the signals that GTK+ widgets emit. Although many of these events result in corresponding signals being emitted, the events are often transformed or filtered along the way.

In some language bindings, the values GDK_2BUTTON_PRESS and GDK_3BUTTON_PRESS would translate into something syntactically invalid (eg Gdk.EventType.2ButtonPress, where a symbol is not allowed to start with a number). In that case, the aliases GDK_DOUBLE_BUTTON_PRESS and GDK_TRIPLE_BUTTON_PRESS can be used instead.

Members

GDK_NOTHING

a special code to indicate a null event.

 

GDK_DELETE

the window manager has requested that the toplevel window be hidden or destroyed, usually when the user clicks on a special icon in the title bar.

 

GDK_DESTROY

the window has been destroyed.

 

GDK_EXPOSE

all or part of the window has become visible and needs to be redrawn.

 

GDK_MOTION_NOTIFY

the pointer (usually a mouse) has moved.

 

GDK_BUTTON_PRESS

a mouse button has been pressed.

 

GDK_2BUTTON_PRESS

a mouse button has been double-clicked (clicked twice within a short period of time). Note that each click also generates a GDK_BUTTON_PRESS event.

 

GDK_DOUBLE_BUTTON_PRESS

alias for GDK_2BUTTON_PRESS, added in 3.6.

 

GDK_3BUTTON_PRESS

a mouse button has been clicked 3 times in a short period of time. Note that each click also generates a GDK_BUTTON_PRESS event.

 

GDK_TRIPLE_BUTTON_PRESS

alias for GDK_3BUTTON_PRESS, added in 3.6.

 

GDK_BUTTON_RELEASE

a mouse button has been released.

 

GDK_KEY_PRESS

a key has been pressed.

 

GDK_KEY_RELEASE

a key has been released.

 

GDK_ENTER_NOTIFY

the pointer has entered the window.

 

GDK_LEAVE_NOTIFY

the pointer has left the window.

 

GDK_FOCUS_CHANGE

the keyboard focus has entered or left the window.

 

GDK_CONFIGURE

the size, position or stacking order of the window has changed. Note that GTK+ discards these events for GDK_WINDOW_CHILD windows.

 

GDK_MAP

the window has been mapped.

 

GDK_UNMAP

the window has been unmapped.

 

GDK_PROPERTY_NOTIFY

a property on the window has been changed or deleted.

 

GDK_SELECTION_CLEAR

the application has lost ownership of a selection.

 

GDK_SELECTION_REQUEST

another application has requested a selection.

 

GDK_SELECTION_NOTIFY

a selection has been received.

 

GDK_PROXIMITY_IN

an input device has moved into contact with a sensing surface (e.g. a touchscreen or graphics tablet).

 

GDK_PROXIMITY_OUT

an input device has moved out of contact with a sensing surface.

 

GDK_DRAG_ENTER

the mouse has entered the window while a drag is in progress.

 

GDK_DRAG_LEAVE

the mouse has left the window while a drag is in progress.

 

GDK_DRAG_MOTION

the mouse has moved in the window while a drag is in progress.

 

GDK_DRAG_STATUS

the status of the drag operation initiated by the window has changed.

 

GDK_DROP_START

a drop operation onto the window has started.

 

GDK_DROP_FINISHED

the drop operation initiated by the window has completed.

 

GDK_CLIENT_EVENT

a message has been received from another application.

 

GDK_VISIBILITY_NOTIFY

the window visibility status has changed.

 

GDK_SCROLL

the scroll wheel was turned

 

GDK_WINDOW_STATE

the state of a window has changed. See GdkWindowState for the possible window states

 

GDK_SETTING

a setting has been modified.

 

GDK_OWNER_CHANGE

the owner of a selection has changed. This event type was added in 2.6

 

GDK_GRAB_BROKEN

a pointer or keyboard grab was broken. This event type was added in 2.8.

 

GDK_DAMAGE

the content of the window has been changed. This event type was added in 2.14.

 

GDK_TOUCH_BEGIN

A new touch event sequence has just started. This event type was added in 3.4.

 

GDK_TOUCH_UPDATE

A touch event sequence has been updated. This event type was added in 3.4.

 

GDK_TOUCH_END

A touch event sequence has finished. This event type was added in 3.4.

 

GDK_TOUCH_CANCEL

A touch event sequence has been canceled. This event type was added in 3.4.

 

GDK_EVENT_LAST

marks the end of the GdkEventType enumeration. Added in 2.18

 

enum GdkEventMask

A set of bit-flags to indicate which events a window is to receive. Most of these masks map onto one or more of the GdkEventType event types above.

GDK_POINTER_MOTION_HINT_MASK is deprecated. It is a special mask to reduce the number of GDK_MOTION_NOTIFY events received. When using GDK_POINTER_MOTION_HINT_MASK, fewer GDK_MOTION_NOTIFY events will be sent, some of which are marked as a hint (the is_hint member is TRUE). To receive more motion events after a motion hint event, the application needs to asks for more, by calling gdk_event_request_motions().

Since GTK 3.8, motion events are already compressed by default, independent of this mechanism. This compression can be disabled with gdk_window_set_event_compression(). See the documentation of that function for details.

If GDK_TOUCH_MASK is enabled, the window will receive touch events from touch-enabled devices. Those will come as sequences of GdkEventTouch with type GDK_TOUCH_UPDATE, enclosed by two events with type GDK_TOUCH_BEGIN and GDK_TOUCH_END (or GDK_TOUCH_CANCEL). gdk_event_get_event_sequence() returns the event sequence for these events, so different sequences may be distinguished.

Members

GDK_EXPOSURE_MASK

receive expose events

 

GDK_POINTER_MOTION_MASK

receive all pointer motion events

 

GDK_POINTER_MOTION_HINT_MASK

deprecated. see the explanation above

 

GDK_BUTTON_MOTION_MASK

receive pointer motion events while any button is pressed

 

GDK_BUTTON1_MOTION_MASK

receive pointer motion events while 1 button is pressed

 

GDK_BUTTON2_MOTION_MASK

receive pointer motion events while 2 button is pressed

 

GDK_BUTTON3_MOTION_MASK

receive pointer motion events while 3 button is pressed

 

GDK_BUTTON_PRESS_MASK

receive button press events

 

GDK_BUTTON_RELEASE_MASK

receive button release events

 

GDK_KEY_PRESS_MASK

receive key press events

 

GDK_KEY_RELEASE_MASK

receive key release events

 

GDK_ENTER_NOTIFY_MASK

receive window enter events

 

GDK_LEAVE_NOTIFY_MASK

receive window leave events

 

GDK_FOCUS_CHANGE_MASK

receive focus change events

 

GDK_STRUCTURE_MASK

receive events about window configuration change

 

GDK_PROPERTY_CHANGE_MASK

receive property change events

 

GDK_VISIBILITY_NOTIFY_MASK

receive visibility change events

 

GDK_PROXIMITY_IN_MASK

receive proximity in events

 

GDK_PROXIMITY_OUT_MASK

receive proximity out events

 

GDK_SUBSTRUCTURE_MASK

receive events about window configuration changes of child windows

 

GDK_SCROLL_MASK

receive scroll events

 

GDK_TOUCH_MASK

receive touch events. Since 3.4

 

GDK_SMOOTH_SCROLL_MASK

receive smooth scrolling events. Since 3.4

 

GDK_ALL_EVENTS_MASK

the combination of all the above event masks.

 

GDK_CURRENT_TIME

#define GDK_CURRENT_TIME     0L

Represents the current time, and can be used anywhere a time is expected.


GdkEventSequence

typedef struct _GdkEventSequence GdkEventSequence;

See Also

Event Structures

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