XGetWindowProperty(3X) XGetWindowProperty(3X)
NAME
XGetWindowProperty, XListProperties, XChangeProperty,
XRotateWindowProperties, XDeleteProperty - obtain and
change window properties
SYNOPSIS
int XGetWindowProperty(display, w, property,
long_offset, long_length, delete, req_type,
actual_type_return,
actual_format_return, nitems_return,
bytes_after_return,
prop_return)
Display *display;
Window w;
Atom property;
long long_offset, long_length;
Bool delete;
Atom req_type;
Atom *actual_type_return;
int *actual_format_return;
unsigned long *nitems_return;
unsigned long *bytes_after_return;
unsigned char **prop_return;
Atom *XListProperties(display, w, num_prop_return)
Display *display;
Window w;
int *num_prop_return;
XChangeProperty(display, w, property, type, format,
mode, data, nelements)
Display *display;
Window w;
Atom property, type;
int format;
int mode;
unsigned char *data;
int nelements;
XRotateWindowProperties(display, w, properties,
num_prop, npositions)
Display *display;
Window w;
Atom properties[];
int num_prop;
int npositions;
XDeleteProperty(display, w, property)
Display *display;
Window w;
Atom property;
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XGetWindowProperty(3X) XGetWindowProperty(3X)
ARGUMENTS
actual_format_return
Returns the actual format of the property.
actual_type_return
Returns the atom identifier that defines the
actual type of the property.
bytes_after_return
Returns the number of bytes remaining to be
read in the property if a partial read was
performed.
data Specifies the property data.
delete Specifies a Boolean value that determines
whether the property is deleted.
display Specifies the connection to the X server.
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 a (char *) in the call to
XChangeProperty.
long_length
Specifies the length in 32-bit multiples of
the data to be retrieved.
long_offset
Specifies the offset in the specified
property (in 32-bit quantities) where the
data is to be retrieved.
mode Specifies the mode of the operation. You can
pass PropModeReplace, PropModePrepend, or
PropModeAppend.
nelements Specifies the number of elements of the
specified data format.
nitems_return
Returns the actual number of 8-bit, 16-bit,
or 32-bit items stored in the prop_return
data.
num_prop Specifies the length of the properties array.
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XGetWindowProperty(3X) XGetWindowProperty(3X)
num_prop_return
Returns the length of the properties array.
npositions
Specifies the rotation amount.
prop_return
Returns a pointer to the data in the
specified format.
property Specifies the property name.
properties
Specifies the array of properties that are to
be rotated.
req_type Specifies the atom identifier associated with
the property type or AnyPropertyType.
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 XGetWindowProperty.
w Specifies the window whose property you want
to obtain, change, rotate or delete.
DESCRIPTION
The XGetWindowProperty 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.
XGetWindowProperty sets the return arguments as
follows:
⊕ If the specified property does not exist for the
specified window, XGetWindowProperty 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, XGetWindowProperty
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.
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XGetWindowProperty(3X) XGetWindowProperty(3X)
⊕ If the specified property exists and either you
assign AnyPropertyType to the req_type argument or
the specified type matches the actual property
type, XGetWindowProperty 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 = actual length of the stored property in bytes
(even if the format is 16 or 32)
I = 4 * long_offset
T = N - I
L = MINIMUM(T, 4 * long_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.
XGetWindowProperty always allocates one extra byte in
prop_return (even if the property is zero length) and
sets it to ASCII null 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, XGetWindowProperty deletes
the property from the window and generates a
PropertyNotify event on the window.
The function returns Success if it executes
successfully. To free the resulting data, use XFree.
XGetWindowProperty can generate BadAtom, BadValue, and
BadWindow errors.
The XListProperties function returns a pointer to an
array of atom properties that are defined for the
specified window or returns NULL if no properties were
found. To free the memory allocated by this function,
use XFree.
XListProperties can generate a BadWindow error.
The XChangeProperty function alters the property for
the specified window and causes the X server to
generate a PropertyNotify event on that window.
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XGetWindowProperty(3X) XGetWindowProperty(3X)
XChangeProperty performs the following:
⊕ If mode is PropModeReplace, XChangeProperty
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.
The lifetime of a property is not tied to the storing
client. Properties remain until explicitly deleted,
until the window is destroyed, or until the server
resets. For a discussion of what happens when the
connection to the X server is closed, see section 2.5.
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.)
XChangeProperty can generate BadAlloc, BadAtom,
BadMatch, BadValue, and BadWindow errors.
The XRotateWindowProperties function allows you to
rotate properties on a window and causes the X server
to generate PropertyNotify events. If the property
names in the properties array are viewed as being
numbered starting from zero and if there are num_prop
property names in the list, then the value associated
with property name I becomes the value associated with
property name (I + npositions) mod N for all I from
zero to N - 1. The effect is to rotate the states by
npositions places around the virtual ring of property
names (right for positive npositions, left for negative
npositions). If npositions mod N is nonzero, the X
server generates a PropertyNotify event for each
property in the order that they are listed in the
array. If an atom occurs more than once in the list or
no property with that name is defined for the window, a
BadMatch error results. If a BadAtom or BadMatch error
results, no properties are changed.
XRotateWindowProperties can generate BadAtom, BadMatch,
and BadWindow errors.
The XDeleteProperty function deletes the specified
property only if the property was defined on the
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XGetWindowProperty(3X) XGetWindowProperty(3X)
specified window and causes the X server to generate a
PropertyNotify event on the window unless the property
does not exist.
XDeleteProperty can generate BadAtom and BadWindow
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.
BadWindow A value for a Window argument does not name a
defined Window.
SEE ALSO
XInternAtom(3X11)
Xlib Programming Manual
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