XGetWindowProperty(3X11)XGetWindowProperty(3X11)NAME
XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindow‐
Properties, 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, nele‐
ments)
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;
ARGUMENTS
Returns the actual format of the property. Returns the atom identifier
that defines the actual type of the property. Returns the number of
bytes remaining to be read in the property if a partial read was per‐
formed. Specifies the property data. Specifies a Boolean value that
determines whether the property is deleted. Specifies the connection
to the X server. 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 XChangeProperty. Specifies the length in 32-bit multiples of the
data to be retrieved. Specifies the offset in the specified property
(in 32-bit quantities) where the data is to be retrieved. Specifies
the mode of the operation. You can pass PropModeReplace, PropMode‐
Prepend, or PropModeAppend. Specifies the number of elements of the
specified data format. Returns the actual number of 8-bit, 16-bit, or
32-bit items stored in the prop_return data. Specifies the length of
the properties array. Returns the length of the properties array.
Specifies the rotation amount. Returns the data in the specified for‐
mat. Specifies the property name. Specifies the array of properties
that are to be rotated. Specifies the atom identifier associated with
the property type or AnyPropertyType. Specifies the type of the prop‐
erty. The X server does not interpret the type but simply passes it
back to an application that later calls XGetWindowProperty. Specifies
the window whose property you want to obtain, change, rotate or delete.
DESCRIPTION
The XGetWindowProperty function returns the actual type of the prop‐
erty; 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. XGetWin‐
dowProperty 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_for‐
mat_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. 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.
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 short 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 long array and should be cast to that type to obtain the elements.
XGetWindowProperty 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, 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 func‐
tion, use XFree.
XListProperties can generate a BadWindow error.
The XChangeProperty function alters the property for the specified win‐
dow and causes the X server to generate a PropertyNotify event on that
window. XChangeProperty performs the following: If mode is PropModeRe‐
place, XChangeProperty discards the previous property value and stores
the new data. If mode is PropModePrepend or PropModeAppend, XChange‐
Property inserts the specified data before the beginning of the exist‐
ing 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 short array.
If the specified format is 32, the property data must be a long array.
The lifetime of a property is not tied to the storing client. Proper‐
ties remain until explicitly deleted, until the window is destroyed, or
until the server resets. For a discussion of what happens when the con‐
nection to the X server is closed, see section 2.6. 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 insuffi‐
cient 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 nposi‐
tions, 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 win‐
dow, 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 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
The server failed to allocate the requested resource or server memory.
A value for an Atom argument does not name a defined Atom. 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. A value for a Window
argument does not name a defined Window.
SEE ALSOXFree(3X11), XInternAtom(3X11)
Xlib -- C Language X Interface
XGetWindowProperty(3X11)
