NAME
XIChangeProperty, XIGetProperty, XIDeleteProperty - change, retrieve or
delete a device´s property.
SYNOPSIS
#include <X11/extensions/XInput2.h>
void XIChangeProperty( Display* dpy,
int deviceid,
Atom property,
Atom type,
int format,
int mode,
unsigned char *data,
int num_items)
void XIDeleteProperty( Display *dpy,
int deviceid,
Atom property)
Status XIGetProperty( Display *dpy,
int deviceid,
Atom property,
long offset,
long length,
Bool delete_property,
Atom type,
Atom *type_return,
int *format_return,
unsigned long *num_items_return,
unsigned long *bytes_after_return,
unsigned char **data)
bytes_after_return
Returns the number of bytes remaining to be read in the prop-
erty if a partial read was performed.
data
Specifies the property data.
display
Specifies the connection to the X server.
delete_property
Specifies a Boolean value that determines whether the property
is to be deleted.
deviceid
The device to list the properties for.
format
Specifies whether the data should be viewed as a list of
8-bit, 16-bit, or 32-bit quantities. Possible values are 8,
16, and 32. This information allows the X server to correctly
perform byte-swap operations as necessary. If the
format is 16-bit or 32-bit, you must explicitly cast your
data pointer to an (unsigned char *) in the call to
XIChangeProperty.
format_return
Returns the actual format of the property.
length
Specifies the length in 32-bit multiples of the data to be
retrieved.
offset
Specifies the offset in the specified property (in 32-bit
quantities) where the data is to be retrieved.
mode
One of PropModeAppend, PropModePrepend or PropModeReplace.
num_items
Number of items in data in the format specified.
nitems_return
Returns the actual number of 8-bit, 16-bit, or 32-bit items
stored in data.
property
Specifies the property name.
type
Specifies the type of the property. The X server does not
interpret the type but simply passes it back to an application
that later calls XIGetProperty.
type_return
Returns the atom identifier that defines the actual type of
the property.
DESCRIPTION
The XIGetProperty function returns the actual type of the property; the
actual format of the property; the number of 8-bit, 16-bit, or 32-bit
items transferred; the number of bytes remaining to be read in the
property; and a pointer to the data actually returned. XIGetProperty
sets the return arguments as follows:
· If the specified property does not exist for the specified device,
XIGetProperty returns None to actual_type_return and the value zero
to actual_format_return and bytes_after_return. The nitems_return
argument is empty. In this case, the delete argument is ignored.
· If the specified property exists but its type does not match the
specified type, XIGetProperty returns the actual property type to
actual_type_return, the actual property format (never zero) to
actual_format_return, and the property length in bytes (even if the
actual_format_return is 16 or 32) to bytes_after_return. It also
ignores the delete argument. The nitems_return argument is empty.
· If the specified property exists and either you assign
AnyPropertyType to the req_type argument or the specified type
matches the actual property type, XIGetProperty returns the actual
property type to actual_type_return and the actual property format
(never zero) to actual_format_return. It also returns a value to
bytes_after_return and nitems_return, by defining the following
values:
N = length of the stored property in bytes
I = 4 * offset
T = N - I
L = MINIMUM(T, 4 * length)
A = N - (I + L)
The returned value starts at byte index I in the property (indexing
from zero), and its length in bytes is L. If the value for long_offset
causes L to be negative, a BadValue error results. The value of
bytes_after_return is A, giving the number of trailing unread bytes in
the stored property.
If the returned format is 8, the returned data is represented as a char
array. If the returned format is 16, the returned data is represented
as a uint16_t array and should be cast to that type to obtain the ele-
ments. If the returned format is 32, the returned data is represented
as a uint32_t array and should be cast to that type to obtain the
elements.
XIGetProperty always allocates one extra byte in prop_return (even if
the property is zero length) and sets it to zero so that simple
properties consisting of characters do not have to be copied into yet
another string before use.
If delete is True and bytes_after_return is zero, XIGetProperty deletes
the property from the window and generates an XIPropertyNotify event on
the window.
The function returns Success if it executes successfully. To free the
resulting data, use XFree.
XIGetProperty can generate BadAtom, BadValue, and BadWindow errors.
The XIChangeProperty function alters the property for the specified
device and causes the X server to generate a XIPropertyNotify event for
that device. XIChangeProperty performs the following:
· If mode is PropModeReplace, XIChangeProperty discards the previous
property value and stores the new data.
· If mode is PropModePrepend or PropModeAppend, XChangeProperty
inserts the specified data before the beginning of the existing
data or onto the end of the existing data, respectively. The type
and format must match the existing property value, or a BadMatch
error results. If the property is undefined, it is treated as
defined with the correct type and format with zero-length data.
If the specified format is 8, the property data must be a char array.
If the specified format is 16, the property data must be a uint16_t
array. If the specified format is 32, the property data must be a
uint32_t array.
The lifetime of a property is not tied to the storing client.
Properties remain until explicitly deleted, until the device is
removed, or until the server resets. The maximum size of a property is
server dependent and can vary dynamically depending on the amount of
memory the server has available. (If there is insufficient space, a
BadAlloc error results.)
XIChangeProperty can generate BadAlloc, BadAtom, BadMatch, BadValue,
and BadDevice errors.
The XIDeleteProperty function deletes the specified property only if
the property was defined on the specified device and causes the X
server to generate a XIPropertyNotify event for the device unless the
property does not exist.
XIDeleteProperty can generate BadAtom and BadDevice errors.
DIAGNOSTICS
BadAlloc The server failed to allocate the requested resource or server
memory.
BadAtom A value for an Atom argument does not name a defined Atom.
BadValue Some numeric value falls outside the range of values accepted
by the 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.
BadDevice An invalid device was specified. The device does not exist.
BadAtom An invalid property was specified. The property does not exist.
SEE ALSO
XIListProperties(3)
[FIXME: source] 10/02/2009