Input Devices
3
GDK Library

# Input Devices

Functions for handling extended input devices

## Synopsis

    #include <gdk/gdk.h>

                        GdkDevice;
    enum                GdkInputSource;
    enum                GdkInputMode;
                        GdkDeviceKey;
                        GdkDeviceAxis;
    enum                GdkAxisUse;
    GList *             gdk_devices_list                    (void);
    void                gdk_device_set_source               (GdkDevice *device,
                                                             GdkInputSource source);
    gboolean            gdk_device_set_mode                 (GdkDevice *device,
                                                             GdkInputMode mode);
    void                gdk_device_set_key                  (GdkDevice *device,
                                                             guint index_,
                                                             guint keyval,
                                                             GdkModifierType modifiers);
    void                gdk_device_set_axis_use             (GdkDevice *device,
                                                             guint index_,
                                                             GdkAxisUse use);
    GdkDevice *         gdk_device_get_core_pointer         (void);

    void                gdk_device_get_state                (GdkDevice *device,
                                                             GdkWindow *window,
                                                             gdouble *axes,
                                                             GdkModifierType *mask);
    gboolean            gdk_device_get_history              (GdkDevice *device,
                                                             GdkWindow *window,
                                                             guint32 start,
                                                             guint32 stop,
                                                             GdkTimeCoord ***events,
                                                             gint *n_events);
    void                gdk_device_free_history             (GdkTimeCoord **events,
                                                             gint n_events);
                        GdkTimeCoord;
    gboolean            gdk_device_get_axis                 (GdkDevice *device,
                                                             gdouble *axes,
                                                             GdkAxisUse use,
                                                             gdouble *value);

    void                gdk_input_set_extension_events      (GdkWindow *window,
                                                             gint mask,
                                                             GdkExtensionMode mode);
    enum                GdkExtensionMode;

## Description

In addition to the normal keyboard and mouse input devices, GTK+ also contains support for extended input devices. In particular, this support is targeted at graphics tablets. Graphics tablets typically return sub-pixel positioning information and possibly information about the pressure and tilt of the stylus. Under X, the support for extended devices is done through the XInput extension.

Because handling extended input devices may involve considerable overhead, they need to be turned on for each GdkWindow individually using `gdk_input_set_extension_events()`. (Or, more typically, for GtkWidgets, using `gtk_widget_set_extension_events()`). As an additional complication, depending on the support from the windowing system, its possible that a normal mouse cursor will not be displayed for a particular extension device. If an application does not want to deal with displaying a cursor itself, it can ask only to get extension events from devices that will display a cursor, by passing the `GDK_EXTENSION_EVENTS_CURSOR` value to `gdk_input_set_extension_events()`. Otherwise, the application must retrieve the device information using `gdk_devices_list()`, check the has_cursor field, and, if it is `FALSE`, draw a cursor itself when it receives motion events.

Each pointing device is assigned a unique integer ID; events from a particular device can be identified by the deviceid field in the event structure. The events generated by pointer devices have also been extended to contain pressure, xtilt and ytilt fields which contain the extended information reported as additional valuators from the device. The pressure field is a a double value ranging from 0.0 to 1.0, while the tilt fields are double values ranging from -1.0 to 1.0. (With -1.0 representing the maximum tilt to the left or up, and 1.0 representing the maximum tilt to the right or down.)

One additional field in each event is the source field, which contains an enumeration value describing the type of device; this currently can be one of `GDK_SOURCE_MOUSE`, `GDK_SOURCE_PEN`, `GDK_SOURCE_ERASER`, or `GDK_SOURCE_CURSOR`. This field is present to allow simple applications to (for instance) delete when they detect eraser devices without having to keep track of complicated per-device settings.

Various aspects of each device may be configured. The easiest way of creating a GUI to allow the user to configure such a device is to use the GtkInputDialog widget in GTK+. However, even when using this widget, application writers will need to directly query and set the configuration parameters in order to save the state between invocations of the application. The configuration of devices is queried using `gdk_devices_list()`. Each device must be activated using `gdk_device_set_mode()`, which also controls whether the device's range is mapped to the entire screen or to a single window. The mapping of the valuators of the device onto the predefined valuator types is set using `gdk_device_set_axis_use()`. And the source type for each device can be set with `gdk_device_set_source()`.

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()`.

The interfaces in this section will most likely be considerably modified in the future to accomodate devices that may have different sets of additional valuators than the pressure xtilt and ytilt.

## Details

### GdkDevice

    typedef struct {
      GObject parent_instance;
      /* All fields are read-only */

      gchar *name;
      GdkInputSource source;
      GdkInputMode mode;
      gboolean has_cursor;	     /* TRUE if the X pointer follows device motion */

      gint num_axes;
      GdkDeviceAxis *axes;

      gint num_keys;
      GdkDeviceKey *keys;
    } GdkDevice;

A GdkDevice structure contains a detailed description of an extended input device. All fields are read-only; but you can use `gdk_device_set_source()`, `gdk_device_set_mode()`, `gdk_device_set_key()` and `gdk_device_set_axis_use()` to configure various aspects of the device.

GObject parent_instance;

  the parent instance

gchar *name;

  the name of this device.

GdkInputSource source;

  the type of this device.

GdkInputMode mode;

  the mode of this device

gboolean has_cursor;

  %TRUE if the pointer follows device motion.

gint num_axes;

  the length of the `axes` array.

GdkDeviceAxis *axes;

  an array of GdkDeviceAxis, describing the axes of this device.

gint num_keys;

  the length of the `keys` array.

GdkDeviceKey *keys;

  an array of GdkDeviceKey, describing the mapped macro buttons of this device.

### enum GdkInputSource

    typedef enum
    {
      GDK_SOURCE_MOUSE,
      GDK_SOURCE_PEN,
      GDK_SOURCE_ERASER,
      GDK_SOURCE_CURSOR
    } GdkInputSource;

An enumeration describing the type of an input device in general terms.

`GDK_SOURCE_MOUSE`

  the device is a mouse. (This will be reported for the core pointer, even if it is something else, such as a trackball.)

`GDK_SOURCE_PEN`

  the device is a stylus of a graphics tablet or similar device.

`GDK_SOURCE_ERASER`

  the device is an eraser. Typically, this would be the other end of a stylus on a graphics tablet.

`GDK_SOURCE_CURSOR`

  the device is a graphics tablet "puck" or similar device.

### enum GdkInputMode

    typedef enum
    {
      GDK_MODE_DISABLED,
      GDK_MODE_SCREEN,
      GDK_MODE_WINDOW
    } GdkInputMode;

An enumeration that describes the mode of an input device.

`GDK_MODE_DISABLED`

  the device is disabled and will not report any events.

`GDK_MODE_SCREEN`

  the device is enabled. The device's coordinate space maps to the entire screen.

`GDK_MODE_WINDOW`

  the device is enabled. The device's coordinate space is mapped to a single window. The manner in which this window is chosen is undefined, but it will typically be the same way in which the focus window for key events is determined.

### GdkDeviceKey

    typedef struct {
      guint keyval;
      GdkModifierType modifiers;
    } GdkDeviceKey;

The GdkDeviceKey structure contains information about the mapping of one device macro button onto a normal X key event. It has the following fields:

guint keyval;

  the keyval to generate when the macro button is pressed. If this is 0, no keypress will be generated.

GdkModifierType modifiers;

  the modifiers set for the generated key event.

### GdkDeviceAxis

    typedef struct {
      GdkAxisUse use;
      gdouble    min;
      gdouble    max;
    } GdkDeviceAxis;

The GdkDeviceAxis structure contains information about the range and mapping of a device axis.

GdkAxisUse use;

  specifies how the axis is used.

gdouble min;

  the minimal value that will be reported by this axis.

gdouble max;

  the maximal value that will be reported by this axis.

### enum GdkAxisUse

    typedef enum
    {
      GDK_AXIS_IGNORE,
      GDK_AXIS_X,
      GDK_AXIS_Y,
      GDK_AXIS_PRESSURE,
      GDK_AXIS_XTILT,
      GDK_AXIS_YTILT,
      GDK_AXIS_WHEEL,
      GDK_AXIS_LAST
    } GdkAxisUse;

An enumeration describing the way in which a device axis (valuator) maps onto the predefined valuator types that GTK+ understands.

`GDK_AXIS_IGNORE`

  the axis is ignored.

`GDK_AXIS_X`

  the axis is used as the x axis.

`GDK_AXIS_Y`

  the axis is used as the y axis.

`GDK_AXIS_PRESSURE`

  the axis is used for pressure information.

`GDK_AXIS_XTILT`

  the axis is used for x tilt information.

`GDK_AXIS_YTILT`

  the axis is used for x tilt information.

`GDK_AXIS_WHEEL`

  the axis is used for wheel information.

`GDK_AXIS_LAST`

  a constant equal to the numerically highest axis value.

### gdk_devices_list ()

    GList *             gdk_devices_list                    (void);

Returns the list of available input devices for the default display. The list is statically allocated and should not be freed.

Returns :

  a list of GdkDevice

### gdk_device_set_source ()

    void                gdk_device_set_source               (GdkDevice *device,
                                                             GdkInputSource source);

Sets the source type for an input device.

`device` :

  a GdkDevice.

`source` :

  the source type.

### gdk_device_set_mode ()

    gboolean            gdk_device_set_mode                 (GdkDevice *device,
                                                             GdkInputMode mode);

Sets a the mode of an input device. The mode controls if the device is active and whether the device's range is mapped to the entire screen or to a single window.

`device` :

  a GdkDevice.

`mode` :

  the input mode.

Returns :

  %TRUE if the mode was successfully changed.

### gdk_device_set_key ()

    void                gdk_device_set_key                  (GdkDevice *device,
                                                             guint index_,
                                                             guint keyval,
                                                             GdkModifierType modifiers);

Specifies the X key event to generate when a macro button of a device is pressed.

`device` :

  a GdkDevice.

`index_` :

  the index of the macro button to set.

`keyval` :

  the keyval to generate.

`modifiers` :

  the modifiers to set.

### gdk_device_set_axis_use ()

    void                gdk_device_set_axis_use             (GdkDevice *device,
                                                             guint index_,
                                                             GdkAxisUse use);

Specifies how an axis of a device is used.

`device` :

  a GdkDevice.

`index_` :

  the index of the axis.

`use` :

  specifies how the axis is used.

### gdk_device_get_core_pointer ()

    GdkDevice *         gdk_device_get_core_pointer         (void);

Returns the core pointer device for the default display.

Returns :

  the core pointer device; this is owned by the display and should not be freed.

### gdk_device_get_state ()

    void                gdk_device_get_state                (GdkDevice *device,
                                                             GdkWindow *window,
                                                             gdouble *axes,
                                                             GdkModifierType *mask);

Gets the current state of a device.

`device` :

  a GdkDevice.

`window` :

  a GdkWindow.

`axes` :

  an array of doubles to store the values of the axes of `device` in, or `NULL`.

`mask` :

  location to store the modifiers, or `NULL`.

### gdk_device_get_history ()

    gboolean            gdk_device_get_history              (GdkDevice *device,
                                                             GdkWindow *window,
                                                             guint32 start,
                                                             guint32 stop,
                                                             GdkTimeCoord ***events,
                                                             gint *n_events);

Obtains the motion history for a device; given a starting and ending timestamp, return all events in the motion history for the device in the given range of time. Some windowing systems do not support motion history, in which case, `FALSE` will be returned. (This is not distinguishable from the case where motion history is supported and no events were found.)

`device` :

  a GdkDevice

`window` :

  the window with respect to which which the event coordinates will be reported

`start` :

  starting timestamp for range of events to return

`stop` :

  ending timestamp for the range of events to return

`events` :

  location to store a newly-allocated array of GdkTimeCoord, or `NULL`

`n_events` :

  location to store the length of `events`, or `NULL`

Returns :

  `TRUE` if the windowing system supports motion history and at least one event was found.

### gdk_device_free_history ()

    void                gdk_device_free_history             (GdkTimeCoord **events,
                                                             gint n_events);

Frees an array of GdkTimeCoord that was returned by `gdk_device_get_history()`.

`events` :

  an array of GdkTimeCoord.

`n_events` :

  the length of the array.

### GdkTimeCoord

    typedef struct {
      guint32 time;
      gdouble axes[GDK_MAX_TIMECOORD_AXES];
    } GdkTimeCoord;

The GdkTimeCoord structure stores a single event in a motion history. It contains the following fields:

guint32 time;

  The timestamp for this event.

gdouble axes[GDK_MAX_TIMECOORD_AXES];

  the values of the device's axes.

### gdk_device_get_axis ()

    gboolean            gdk_device_get_axis                 (GdkDevice *device,
                                                             gdouble *axes,
                                                             GdkAxisUse use,
                                                             gdouble *value);

Interprets an array of double as axis values for a given device, and locates the value in the array for a given axis use.

`device` :

  a GdkDevice

`axes` :

  pointer to an array of axes

`use` :

  the use to look for

`value` :

  location to store the found value.

Returns :

  `TRUE` if the given axis use was found, otherwise `FALSE`

### gdk_input_set_extension_events ()

    void                gdk_input_set_extension_events      (GdkWindow *window,
                                                             gint mask,
                                                             GdkExtensionMode mode);

Turns extension events on or off for a particular window, and specifies the event mask for extension events.

`window` :

  a GdkWindow.

`mask` :

  the event mask

`mode` :

  the type of extension events that are desired.

### enum GdkExtensionMode

    typedef enum
    {
      GDK_EXTENSION_EVENTS_NONE,
      GDK_EXTENSION_EVENTS_ALL,
      GDK_EXTENSION_EVENTS_CURSOR
    } GdkExtensionMode;

An enumeration used to specify which extension events are desired for a particular widget.

`GDK_EXTENSION_EVENTS_NONE`

  no extension events are desired.

`GDK_EXTENSION_EVENTS_ALL`

  all extension events are desired.

`GDK_EXTENSION_EVENTS_CURSOR`

  extension events are desired only if a cursor will be displayed for the device.