XIQUERYDEVICE(3)

NAME
XIQueryDevice, XIFreeDeviceInfo - get information about devices.

SYNOPSIS

#include <X11/extensions/XInput2.h>

XIDeviceInfo* XIQueryDevice( Display *display,
                             int deviceid,
                             int *ndevices_return);

XIFreeDeviceInfo( XIDeviceInfo *info);

deviceid
       Specifies the device to query or XIAllDevices or
       XIAllMasterDevices.

display
       Specifies the connection to the X server.

ndevices_return
       Returns the number of devices returned.

info
       A list of device XIDeviceInfo structs to be freed.

DESCRIPTION

    The XIQueryDevice returns information about one or more input
    devices. If the deviceid specifies a device, ndevices_return is
    1 and the returned information describes only the requested
    device. If deviceid is XIAllDevices or XIAllMasterDevices,
    ndevices_return is the number of devices or master devices,
    respectively, and the returned information represents all
    devices or all master devices, respectively.

    To free the XIDeviceInfo array returned by XIQueryDevice, use
    XIFreeDeviceInfo.

    For each input device requested, the XIQueryDevice returns an
    XIDeviceInfo structure. Each structure contains information
    about the capabilities of one input device available to the
    server.

    typedef struct
    {
        int                 deviceid;
        char                *name;
        int                 use;
        int                 attachment;
        Bool                enabled;
        int                 num_classes;
        XIAnyClassInfo      **classes;
    } XIDeviceInfo;

    The deviceid is the numeric unique id of the device. A deviceid
    is unique for the life-time of a device but a server may re-use
    the id once a device has been removed.

    The name points to a null-terminated string specifying the
    identifier of the device.

    The use and attachment fields specify the type of the device
    and the current attachment or pairing.
    - If use is XIMasterPointer, the device is a master pointer and
      attachment specifies the deviceid of the paired master
      keyboard.
    - If use is XIMasterKeyboard, the device is a master keyboard,
      and the attachment field specifies the paired master pointer.
    - If use is XISlavePointer, the device is a slave device and
      currently attached to the master pointer specified in
      attachement.
    - If use is XISlaveKeyboard, the device is a slave device an
      currently attached to the master keyboard specified in
      attachment.
    - If use is XIFloatingSlave, the device is a slave device
      currently not attached to any master device. The value of the
      attachment field for floating slave devices is undefined.

    The enabled field specifies if the device is currently enabled
    and can send events. Disabled devices will not send events.

    The num_classes field specifies the number of input classes
    pointed to by classes. The first two fields of all input
    classes are identical.

    typedef struct
    {
        int         type;
        int         sourceid;
    } XIAnyClassInfo;

    The type field specifies the type of the input class.
    Currently, the following types are defined:
        XIKeyClass, XIButtonClass, XIValuatorClass, XIScrollClass,
        XITouchClass

    In the future, additional types may be added. Clients are
    required to ignore unknown input classes.

    The sourceid is the deviceid this class originated from. For
    master devices, the sourceid is typically the id of the slave
    device currently sending events. For slave devices, the
    sourceid is typically the device's id.

    A device may have zero or one XIButtonClass, denoting the
    device's capability to send button events.

    typedef struct {
        int           mask_len;
        unsigned char *mask;
    } XIButtonState;

    typedef struct
    {
        int         type;
        int         sourceid;
        int         num_buttons;
        Atom        *labels;
        XIButtonState state;
    } XIButtonClassInfo;

    The num_buttons field specifies the number of buttons available
    on this device. A device that has an XIButtonClass must have at
    least one button.

    labels is a list of num_buttons Atoms specifying the button
    labels for this device. If the label is not None, then the
    label specifies the type of button in physical device order
    (i.e. as the buttons are numbered on the physical input
    device).

    The state is the current button state as seen by clients (i.e.
    after button mapping is applied). The mask_len field specifies
    the length of mask in bytes. For each button on the device, the
    respective bit in mask is set if the button is currently
    logically down.

    A device may have zero or one XIKeyClass, denoting the device's
    capability to send key events.

    typedef struct
    {
        int         type;
        int         sourceid;
        int         num_keycodes;
        int         *keycodes;
    } XIKeyClassInfo;

    The num_keycodes field specifies the number of keycodes
    available on this device. A device that has an XIKeyClass must
    have at least one keycode.

    keycodes is a list of num_keycodes keycodes the device may
    send.

    A device may have zero or more XIValuatorClass, denoting the
    device's capability to send coordinates.

    typedef struct
    {
        int         type;
        int         sourceid;
        int         number;
        Atom        label;
        double      min;
        double      max;
        double      value;
        int         resolution;
        int         mode;
    } XIValuatorClassInfo;

    The number field specifies the number of the axis on the
    physical device.

    If the label field is not None, the value of label is an Atom
    describing the axis.

    min and max are the minimum and maximum values allowed on this
    axis. If both are zero, no minumum or maximum values are set on
    this device. value is the current value of this axis.

    The resolution field specifies the resolution of the device in
    units/m.

    The mode specifies the mode of this axis. If the mode is
    XIModeAbsolute this axis sends absolute coordinates. If the
    mode is XIModeRelative, this device sends relative coordinates.

    typedef struct
    {
        int         type;
        int         sourceid;
        int         number;
        int         scroll_type;
        double      increment;
        int         flags;
    } XIScrollClassInfo;

    This class describes scrolling capability on a valuator. For
    each XIScrollClassInfo, an XIValuatorClassInfo with the same
    number is present on the device.

    The number field specifies the valuator number on the physical
    device that this scroll information applies to. See the
    respective XIValuatorClassInfo for detailed information on this
    valuator.

    The scroll_type field specifies the type of scrolling, either
    XIScrollTypeVertical or XIScrollTypeHorizontal.

    The increment specifies the value change considered one unit of
    scrolling down.

    The flags field specifies flags that apply to this scrolling
    information:

    If XIScrollFlagNoEmulation is set, the server will not
    emulate legacy button events for valuator changes on this
    valuator.

    If XIScrollFlagPreferred is set, this axis is the
    preferred axis for this scroll type and will be used for
    the emulation of XI_Motion events when the driver submits
    legacy scroll button events.

    typedef struct
    {
        int         type;
        int         sourceid;
        int         mode;
        int         num_touches;
    } XITouchClassInfo;

    A device may have zero or one XITouchClassInfo, denoting
    multi-touch capability on the device. A device with a XITouchClassInfo
    may send TouchBegin, TouchUpdate, TouchEnd and TouchOwnership events.

    The mode field is either XIDirectTouch for direct-input touch devices
    such as touchscreens or XIDependentTouch for indirect input devices such
    as touchpads. For XIDirectTouch devices, touch events are sent to window
    at the position the touch occured. For XIDependentTouch devices, touch
    events are sent to the window at the position of the device's sprite.

    The num_touches field defines the maximum number of simultaneous touches
    the device supports. A num_touches of 0 means the maximum number of
    simultaneous touches is undefined or unspecified. This field should be
    used as a guide only, devices will lie about their capabilities.

    A device with an XITouchClassInfo may still send pointer events. The
    valuators must be defined with the respective XIValuatorClass
    classes. A valuator may send both pointer and touch-events.

    XIQueryDevice can generate a BadDevice error.

    XIFreeDeviceInfo frees the information returned by
    XIQueryDevice.

DIAGNOSTICS

    BadDevice
           An invalid device was specified. The device does not
           exist or is not a pointer device.