Free Knowledge Resources


Linux Manual Pages


Free Software * Books

Source Code

Free Media

Linux

XLISTINPUTDEVICES



XLISTINPUTDEVICES

NAME
SYNOPSIS
DESCRIPTION

NAME

XListInputDevices, XFreeDeviceList − list available input devices

SYNOPSIS

#include <X11/extensions/XInput.h>

XDeviceInfo *XListInputDevices( Display *display,
int *ndevices_return);

int XFreeDeviceList( XDeviceInfo *list);

display
Specifies the connection to the X server.

ndevices_return
Specifies a pointer to a variable where the number of
available devices canbe returned.

list
Specifies the list of devices to free. The
XFreeDeviceList functionfrees the list of available
extension input devices.

DESCRIPTION

The XListInputDevices request lists the available input
devices. This list includes the core keyboard and any physical
input device currently accessible through the X server, and any
input devices that are not currently accessible through the X
server but could be accessed if requested.

A master pointer is a virtual pointer device that does not
represent a physical device. It is visually represented through
a cursor. A master keyboard is a virtual keyboard device that
does not represent a physical device. It is virtually
representd through a keyboard focus. A master pointer and a
master keyboard are always paired (i.e. if shift is pressed on
the master keyboard, a pointer click would be a shift−click).
Multiple master pointer/keyboard pairs can exist.

X servers supporting the X Input Extension version 2,
XListInputDevices only returns the first master pointer, the
first master keyboard and all slave devices. Additional master
devices are not listed.

Physical devices (so−called slave devices) are attached to
either a master pointer or a master keyboard, depending on
their capabilities. If a slave device generates an event, the
event is also generated by the respective master device.
Multiple slave devices can be attached to a single master
device.

Some server implementations may make all physical input devices
available at the time the server is initialized. Others may
wait until requested by a client to access an input device. In
the latter case, it is possible that an input device will be
listed as available at one time but not at another.

For each input device available to the server, the
XListInputDevices request returns an XDeviceInfo structure.
That structure contains a pointer to a list of structures, each
of which contains information about one class of input
supported by the device. The XDeviceInfo structure is defined
as follows:
typedef struct _XDeviceInfo {
XID id;
Atom type;
char *name;
int num_classes;
int use;
XAnyClassPtr inputclassinfo;
} XDeviceInfo;

The id is a number in the range 0−128 that uniquely identifies
the device. It is assigned to the device when it is initialized
by the server.

The type field is of type Atom and indicates the nature of the
device. The type will correspond to one of the following strings
(defined in the header file XI.h):

XI_MOUSE XI_TABLET XI_KEYBOARD XI_TOUCHSCREEN XI_TOUCHPAD
XI_BUTTONBOX XI_BARCODE XI_TRACKBALL XI_QUADRATURE XI_ID_MODULE
XI_ONE_KNOB XI_NINE_KNOB XI_KNOB_BOX XI_SPACEBALL XI_DATAGLOVE
XI_EYETRACKER XI_CURSORKEYS XI_FOOTMOUSE XI_JOYSTICK

These strings may be used in an XInternAtom request to return
an atom that can be compared with the type field of the
XDeviceInfo structure.

The name field contains a pointer to a null−terminated string
that serves as identifier of the device. This identifier may be
user−configured or automatically assigned by the server.

The num_classes field is a number in the range 0−255 that
specifies the number of input classes supported by the device
for which information is returned by ListInputDevices. Some
input classes, such as class Focus and class Proximity do not
have any information to be returned by ListInputDevices.

All devices provide an AttachClass. This class specifies the
master device a given slave device is attached to. For master
devices, the class specifies the respective paired master
device.

The use field specifies how the device is currently being used.
If the value is IsXKeyboard, the device is a master keyboard.
If the value is IsXPointer, the device is a master pointer. If
the value is IsXExtensionPointer, the device is a slave
pointer. If the value is IsXExtensionKeyboard, the device is a
slave keyboard. If the value is IsXExtensionDevice, the device
is available for use as an extension device.

The inputclassinfo field contains a pointer to the first
input−class specific data. The first two fields are common to
all classes.

The class field is a number in the range 0−255. It uniquely
identifies the class of input for which information is
returned. Currently defined classes are KeyClass, ButtonClass,
and ValuatorClass.

The length field is a number in the range 0− 255. It specifies
the number of bytes of data that are contained in this input
class. The length includes the class and length fields.

The XKeyInfo structure describes the characteristics of the
keys on the device. It is defined as follows:

typedef struct _XKeyInfo {
XID class;
int length;
unsigned short min_keycode;
unsigned short max_keycode;
unsigned short num_keys;
} XKeyInfo;

min_keycode is of type KEYCODE. It specifies the minimum
keycode that the device will report. The minimum keycode will
not be smaller than 8.

max_keycode is of type KEYCODE. It specifies the maximum
keycode that the device will report. The maximum keycode will
not be larger than 255.

num_keys specifies the number of keys that the device has.

The XButtonInfo structure defines the characteristics of the
buttons on the device. It is defined as follows:

typedef struct _XButtonInfo {
XID class;
int length;
short num_buttons;
} XButtonInfo;

num_buttons specifies the number of buttons that the device
has.

The XValuatorInfo structure defines the characteristics of the
valuators on the device. It is defined as follows:

typedef struct _XValuatorInfo {
XID class;
int length;
unsigned char num_axes;
unsigned char mode;
unsigned long motion_buffer;
XAxisInfoPtr axes;
} XValuatorInfo;

num_axes contains the number of axes the device supports.

mode is a constant that has one of the following values:
Absolute or Relative. Some devices allow the mode to be changed
dynamically via the SetDeviceMode request.

motion_buffer_size is a cardinal number that specifies the
number of elements that can be contained in the motion history
buffer for the device.

The axes field contains a pointer to an XAxisInfo structure.

The XAxisInfo structure is defined as follows:

typedef struct _XAxisInfo {
int resolution;
int min_value;
int max_value;
} XAxisInfo;

The resolution contains a number in counts/meter.

The min_val field contains a number that specifies the minimum
value the device reports for this axis. For devices whose mode
is Relative, the min_val field will contain 0.

The max_val field contains a number that specifies the maximum
value the device reports for this axis. For devices whose mode
is Relative, the max_val field will contain 0.

The XAttachInfo structure is defined as follows:
typedef struct _XAttachInfo {
int attached;
} XAttachInfo;

If the device is a slave device, attached specifies the device
ID of the master device this device is attached to. If the
device is not attached to a master device, attached is
Floating. If the device is a master device, attached specifies
the device ID of the master device this device is paired with.

To free the XDeviceInfo array created by XListInputDevices, use
XFreeDeviceList.




Opportunity


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.



Free Software


Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.



Free Books


The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.



Education


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.


birds banner