---
name: "XGetFeedbackControl"
section: "3x"
platform: "linux"
package: "libxi-dev"
version: "4.3.0.dfsg.1-14sarge7"
release: "Debian 3.1 (Sarge)"
platforms: ["linux"]
url: "https://new.carta.tech/XGetFeedbackControl/3x"
---

# XGetFeedbackControl(3x)

query and change input device feedbacks

## NAME

XGetFeedbackControl, XChangeFeedbackControl - query and change input device feedbacks

## SYNTAX

XFeedbackState \*XGetFeedbackControl(Display \**display*, XDevice \**device*, int \**num\_feedbacks*);

int XChangeFeedbackControl(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*