Table of Contents

## Name

XGetFeedbackControl, XChangeFeedbackControl - query and change input device feedbacks

## Syntax

XFeedbackState * XGetFeedbackControl(display, device, num_feedbacks)
Display *display;
XDevice *device;
int *num_feedbacks;

int XChangeFeedbackControl(display, device, mask, control)
Display *display;
XDevice *device;
Mask mask;
XFeedbackControl *control;

## Arguments

display
  Specifies the connection to the X server.
device
  Specifies the device whose feedbacks are to be queried or modified.
num_feedbacks
  Specifies an address into which the number of feedbacks supported by the device is to be returned.
mask
  Specifies a mask specific to each type of feedback that describes how the feedback is to be modified.
control
  Specifies the address of an XFeedbackControl structure that contains the new values for the feedback.

## Description

These requests are provided to manipulate those input devices that support feedbacks. A BadMatch error will be generated if the requested device does not support feedbacks. Whether or not a given device supports feedbacks can be determined by examining the information returned by the XOpenDevice request. For those devices that support feedbacks, XOpenDevice will return an XInputClassInfo structure with the input_class field equal to the constant FeedbackClass (defined in the file XI.h).

The XGetFeedbackControl request returns a pointer to a list of XFeedbackState structures. Each item in this list describes one of the feedbacks supported by the device. The items are variable length, so each contains its length to allow traversal to the next item in the list.

The feedback classes that are currently defined are: KbdFeedbackClass, PtrFeedbackClass, StringFeedbackClass, IntegerFeedbackClass, LedFeedbackClass, and BellFeedbackClass. These constants are defined in the file XI.h. An input device may support zero or more classes of feedback, and may support multiple feedbacks of the same class. Each feedback contains a class identifier and an id that is unique within that class for that input device. The id is used to identify the feedback when making an XChangeFeedbackControl request.

XGetFeedbackControl can generate a BadDevice or BadMatch error.

The XChangeFeedbackControl request modifies the values of one feedback on the specified device. The feedback is identified by the id field of the XFeedbackControl structure that is passed with the request. The fields of the feedback that are to be modified are identified by the bits of the mask that is passed with the request.

XChangeFeedbackControl can generate a BadDevice, BadMatch, or BadValue error.

## Structures

Each class of feedback is described by a structure specific to that class. These structures are defined in the file XInput.h. XFeedbackState and XFeedbackControl are generic structures that contain three fields that are at the beginning of each class of feedback:

typedef struct {
`` `` XID class;
`` `` int length;
`` `` XID id;
} XFeedbackState, XFeedbackControl;

The XKbdFeedbackState structure defines the attributes that are returned for feedbacks equivalent to those on the X keyboard.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     click;
        int     percent;
        int     pitch;
        int     duration;
        int     led_mask;
        int     global_auto_repeat;
        char    auto_repeats[32];
    } XKbdFeedbackState;

The XPtrFeedbackState structure defines the attributes that are returned for feedbacks equivalent to those on the the X pointer.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     accelNum;
        int     accelDenom;
        int     threshold;
    } XPtrFeedbackState;

The XIntegerFeedbackState structure defines attributes that are returned for integer feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     resolution;
        int     minVal;
        int     maxVal;
    } XIntegerFeedbackState;

The XStringFeedbackState structure defines the attributes that are returned for string feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     max_symbols;
        int     num_syms_supported;
        KeySym  *syms_supported;
    } XStringFeedbackState;

The XBellFeedbackState structure defines the attributes that are returned for bell feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     percent;
        int     pitch;
        int     duration;
    } XBellFeedbackState;

The XLedFeedbackState structure defines the attributes that are returned for LED feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     led_values;
    } XLedFeedbackState;

The XPrtFeedbackControl structure defines the attributes that can be controlled for pointer feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     accelNum;
        int     accelDenom;
        int     threshold;
    } XPtrFeedbackControl;

The XKbdFeedbackControl structure defines the attributes that can be controlled for keyboard feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     click;
        int     percent;
        int     pitch;
        int     duration;
        int     led_mask;
        int     led_value;
        int     key;
        int     auto_repeat_mode;
    } XKbdFeedbackControl;

The XStringFeedbackControl structure defines the attributes that can be controlled for string feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     num_keysyms;
        KeySym  *syms_to_display;
    } XStringFeedbackControl;

The XIntegerFeedbackControl structure defines the attributes that can be controlled for integer feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     int_to_display;
    } XIntegerFeedbackControl;

The XBellFeedbackControl structure defines the attributes that can be controlled for bell feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     percent;
        int     pitch;
        int     duration;
    } XBellFeedbackControl;

The XLedFeedbackControl structure defines the attributes that can be controlled for LED feedbacks.

    typedef struct {
        XID     class;
        int     length;
        XID     id;
        int     led_mask;
        int     led_values;
    } XLedFeedbackControl;

## Diagnostics

BadDevice
  An invalid device was specified. The specified device does not exist or has not been opened by this client via XOpenInputDevice. This error may also occur if some other client has caused the specified device to become the X keyboard or X pointer device via the XChangeKeyboardDevice or XChangePointerDevice requests.
BadMatch
  This error may occur if an XGetFeedbackControl request was made specifying a device that has no feedbacks, or an XChangeFeedbackControl request was made with an XFeedbackControl structure that contains an invalid feedback type. It may also occur if an invalid combination of mask bits is specified (DvKey but no DvAutoRepeatMode for keyboard feedbacks), or if an invalid KeySym is specified for a string feedback.
BadValue
  Some numeric value falls outside the range of values accepted by the XChangeFeedbackControl request. Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument defined as a set of alternatives can generate this error.

## See Also

Programming With Xlib

Table of Contents

- Name
- Syntax
- Arguments
- Description
- Structures
- Diagnostics
- See Also