XGetWindowProperty(3X11) X Version 11(Release 5) XGetWindowProperty(3X11)
NAME
XGetWindowProperty, XListProperties, XChangeProperty,
XRotateWindowProperties, XDeleteProperty - obtain and change window
properties
SYNTAX
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(3X11) X Version 11(Release 5) XGetWindowProperty(3X11)
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 an
(unsigned 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.
num_prop_return
Returns the length of the properties array.
npositions
Specifies the rotation amount.
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XGetWindowProperty(3X11) X Version 11(Release 5) XGetWindowProperty(3X11)
prop_return
Returns 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.
⊕ 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)
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XGetWindowProperty(3X11) X Version 11(Release 5) XGetWindowProperty(3X11)
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. 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 2.6. 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 insufficient
space, a BadAlloc error results.)
XChangeProperty can generate BadAlloc, BadAtom, BadMatch, BadValue, and
BadWindow errors.
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XGetWindowProperty(3X11) X Version 11(Release 5) XGetWindowProperty(3X11)
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 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
XFree(3X11), XInternAtom(3X11)
Xlib - C Language X Interface
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