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In addition to a single pointer and keyboard for user interface input, GDK contains support for a variety of input devices, including graphics tablets, touchscreens and multiple pointers/keyboards interacting simultaneously with the user interface. Such input devices often have additional features, such as sub-pixel positioning information and additional device-dependent information.
In order to query the device hierarchy and be aware of changes in the device hierarchy (such as virtual devices being created or removed, or physical devices being plugged or unplugged), GDK provides GdkDeviceManager.
By default, and if the platform supports it, GDK is aware of multiple
keyboard/pointer pairs and multitouch devices. This behavior can be
changed by calling gdk_disable_multidevice() before gdk_display_open().
There should rarely be a need to do that though, since GDK defaults
to a compatibility mode in which it will emit just one enter/leave
event pair for all devices on a window. To enable per-device
enter/leave events and other multi-pointer interaction features,
gdk_window_set_support_multidevice() must be called on
GdkWindows (or gtk_widget_set_support_multidevice() on widgets).
window. See the gdk_window_set_support_multidevice() documentation
for more information.
On X11, multi-device support is implemented through XInput 2.
Unless gdk_disable_multidevice() is called, the XInput 2
GdkDeviceManager implementation will be used as the input source.
Otherwise either the core or XInput 1 implementations will be used.
For simple applications that don’t have any special interest in
input devices, the so-called “client pointer”
provides a reasonable approximation to a simple setup with a single
pointer and keyboard. The device that has been set as the client
pointer can be accessed via gdk_device_manager_get_client_pointer().
Conceptually, in multidevice mode there are 2 device types. Virtual devices (or master devices) are represented by the pointer cursors and keyboard foci that are seen on the screen. Physical devices (or slave devices) represent the hardware that is controlling the virtual devices, and thus have no visible cursor on the screen.
Virtual devices are always paired, so there is a keyboard device for every
pointer device. Associations between devices may be inspected through
gdk_device_get_associated_device().
There may be several virtual devices, and several physical devices could be controlling each of these virtual devices. Physical devices may also be “floating”, which means they are not attached to any virtual device.
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carlos@sacarino:~$ xinput list ⎡ Virtual core pointer id=2 [master pointer (3)] ⎜ ↳ Virtual core XTEST pointer id=4 [slave pointer (2)] ⎜ ↳ Wacom ISDv4 E6 Pen stylus id=10 [slave pointer (2)] ⎜ ↳ Wacom ISDv4 E6 Finger touch id=11 [slave pointer (2)] ⎜ ↳ SynPS/2 Synaptics TouchPad id=13 [slave pointer (2)] ⎜ ↳ TPPS/2 IBM TrackPoint id=14 [slave pointer (2)] ⎜ ↳ Wacom ISDv4 E6 Pen eraser id=16 [slave pointer (2)] ⎣ Virtual core keyboard id=3 [master keyboard (2)] ↳ Virtual core XTEST keyboard id=5 [slave keyboard (3)] ↳ Power Button id=6 [slave keyboard (3)] ↳ Video Bus id=7 [slave keyboard (3)] ↳ Sleep Button id=8 [slave keyboard (3)] ↳ Integrated Camera id=9 [slave keyboard (3)] ↳ AT Translated Set 2 keyboard id=12 [slave keyboard (3)] ↳ ThinkPad Extra Buttons id=15 [slave keyboard (3)] |
By default, GDK will automatically listen for events coming from all
master devices, setting the GdkDevice for all events coming from input
devices. Events containing device information are GDK_MOTION_NOTIFY,
GDK_BUTTON_PRESS, GDK_2BUTTON_PRESS, GDK_3BUTTON_PRESS,
GDK_BUTTON_RELEASE, GDK_SCROLL, GDK_KEY_PRESS, GDK_KEY_RELEASE,
GDK_ENTER_NOTIFY, GDK_LEAVE_NOTIFY, GDK_FOCUS_CHANGE,
GDK_PROXIMITY_IN, GDK_PROXIMITY_OUT, GDK_DRAG_ENTER, GDK_DRAG_LEAVE,
GDK_DRAG_MOTION, GDK_DRAG_STATUS, GDK_DROP_START, GDK_DROP_FINISHED
and GDK_GRAB_BROKEN. When dealing with an event on a master device,
it is possible to get the source (slave) device that the event originated
from via gdk_event_get_source_device().
On a standard session, all physical devices are connected by default to the "Virtual Core Pointer/Keyboard" master devices, hence routing all events through these. This behavior is only modified by device grabs, where the slave device is temporarily detached for as long as the grab is held, and more permanently by user modifications to the device hierarchy.
On certain application specific setups, it may make sense
to detach a physical device from its master pointer, and mapping it to
an specific window. This can be achieved by the combination of
gdk_device_grab() and gdk_device_set_mode().
In order to listen for events coming from devices
other than a virtual device, gdk_window_set_device_events() must be
called. Generally, this function can be used to modify the event mask
for any given device.
Input devices may also provide additional information besides X/Y.
For example, graphics tablets may also provide pressure and X/Y tilt
information. This information is device-dependent, and may be
queried through gdk_device_get_axis(). In multidevice mode, virtual
devices will change axes in order to always represent the physical
device that is routing events through it. Whenever the physical device
changes, the “n-axes” property will be notified, and
gdk_device_list_axes() will return the new device axes.
Devices may also have associated “keys” or
macro buttons. Such keys can be globally set to map into normal X
keyboard events. The mapping is set using gdk_device_set_key().
In GTK+ 3.20, a new GdkSeat object has been introduced that supersedes GdkDeviceManager and should be preferred in newly written code.
void
gdk_disable_multidevice (void);
Disables multidevice support in GDK. This call must happen prior
to gdk_display_open(), gtk_init(), gtk_init_with_args() or
gtk_init_check() in order to take effect.
Most common GTK+ applications won’t ever need to call this. Only applications that do mixed GDK/Xlib calls could want to disable multidevice support if such Xlib code deals with input devices in any way and doesn’t observe the presence of XInput 2.
Since: 3.0
GdkDisplay *
gdk_device_manager_get_display (GdkDeviceManager *device_manager);
Gets the GdkDisplay associated to device_manager
.
the GdkDisplay to which
device_manager
is associated to, or NULL. This memory is
owned by GDK and must not be freed or unreferenced.
[nullable][transfer none]
Since: 3.0
GList * gdk_device_manager_list_devices (GdkDeviceManager *device_manager,GdkDeviceType type);
gdk_device_manager_list_devices has been deprecated since version 3.20 and should not be used in newly-written code.
, use gdk_seat_get_pointer(), gdk_seat_get_keyboard()
and gdk_seat_get_slaves() instead.
Returns the list of devices of type type
currently attached to
device_manager
.
a list of
GdkDevices. The returned list must be
freed with g_list_free(). The list elements are owned by
GTK+ and must not be freed or unreffed.
[transfer container][element-type Gdk.Device]
Since: 3.0
GdkDevice *
gdk_device_manager_get_client_pointer (GdkDeviceManager *device_manager);
gdk_device_manager_get_client_pointer has been deprecated since version 3.20 and should not be used in newly-written code.
Use gdk_seat_get_pointer() instead.
Returns the client pointer, that is, the master pointer that acts as the core pointer for this application. In X11, window managers may change this depending on the interaction pattern under the presence of several pointers.
You should use this function seldomly, only in code that isn’t triggered by a GdkEvent and there aren’t other means to get a meaningful GdkDevice to operate on.
The client pointer. This memory is owned by GDK and must not be freed or unreferenced.
[transfer none]
Since: 3.0
“display” property“display” GdkDisplay *
Display for the device manager.
Owner: GdkDeviceManager
Flags: Read / Write / Construct Only
“device-added” signalvoid user_function (GdkDeviceManager *device_manager, GdkDevice *device, gpointer user_data)
The ::device-added signal is emitted either when a new master pointer is created, or when a slave (Hardware) input device is plugged in.
device_manager |
the object on which the signal is emitted |
|
device |
the newly added GdkDevice. |
|
user_data |
user data set when the signal handler was connected. |
Flags: Run Last
“device-changed” signalvoid user_function (GdkDeviceManager *device_manager, GdkDevice *device, gpointer user_data)
The ::device-changed signal is emitted whenever a device has changed in the hierarchy, either slave devices being disconnected from their master device or connected to another one, or master devices being added or removed a slave device.
If a slave device is detached from all master devices
(gdk_device_get_associated_device() returns NULL), its
GdkDeviceType will change to GDK_DEVICE_TYPE_FLOATING,
if it's attached, it will change to GDK_DEVICE_TYPE_SLAVE.
device_manager |
the object on which the signal is emitted |
|
device |
the GdkDevice that changed. |
|
user_data |
user data set when the signal handler was connected. |
Flags: Run Last
“device-removed” signalvoid user_function (GdkDeviceManager *device_manager, GdkDevice *device, gpointer user_data)
The ::device-removed signal is emitted either when a master pointer is removed, or when a slave (Hardware) input device is unplugged.
device_manager |
the object on which the signal is emitted |
|
device |
the just removed GdkDevice. |
|
user_data |
user data set when the signal handler was connected. |
Flags: Run Last