g-object, common-lisp:standard-object, common-lisp:t

None

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 the gdk-device-manager object.

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 the gdk-disable-multidevice function before the gdk-display-open function. 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, the gdk-window-support-multidevice function must be called on gdk-window objects, or the gtk-widget-support-multidevice function on widgets. See the gdk-window-support-multidevice documentation for more information.

On X11, multi-device support is implemented through XInput 2. Unless the gdk-disable-multidevice function is called, the XInput 2 gdk-device-manager implementation will be used as the input source. Otherwise either the core or XInput 1 implementations will be used.

For simple applications that do not 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 the gdk-device-manager-client-pointer function.

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 the gdk-device-associated-device function.

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.

Example: Master and slave devices

 carlossacarino:~$ 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 gdk-device object for all events coming from input devices. Events containing device information are :motion-notify, :button-press, :2button-press, :3button-press, :button-release, :scroll, :key-press, :key-release, :enter-notify, :leave-notify, :focus-change, :proximity-in, :proximity-out, :drag-enter, :drag-leave, :drag-motion, :drag-status, :drop-start, :drop-finished and :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 the gdk-event-source-device function.

In order to listen for events coming from devices other than a virtual device, the gdk-window-device-events function 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 the gdk-device-axis function. 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 the gdk-device-list-axes function 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 the gdk-device-key function.

In GTK 3.20, a new gdk-seat object has been introduced that supersedes the gdk-device-manager object and should be preferred in newly written code.

The "device-added" signal

 lambda (manager device)    :run-last      

The signal is emitted either when a new master pointer is created, or when a slave (hardware) input device is plugged in.

manager

The gdk-device-manager object on which the signal is emitted.

device

The newly added gdk-device object.

The "device-changed" signal

 lambda (manager device)    :run-last      

The 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 its gdk-device-type value will change to the :floating value, if it is attached, it will change to the :slave value.

manager

The gdk-device-manager object on which the signal is emitted.

device

The gdk-device object that changed.

The "device-removed" signal

 lambda (manager device)    :run-last      

The signal is emitted either when a master pointer is removed, or when a slave (hardware) input device is unplugged.

manager

The gdk-device-manager object on which the signal is emitted.

device

The just removed gdk-device object.