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XGetWindowProperty(3)		XLIB FUNCTIONS		 XGetWindowProperty(3)

NAME
       XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindow-
       Properties, XDeleteProperty - obtain and	change window properties

SYNTAX
       int XGetWindowProperty(Display *display,	Window w, Atom property, long
	      long_offset, long	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 *display, Window w, int *num_prop_re-
	      turn);

       int XChangeProperty(Display *display, Window w, Atom property, Atom
	      type, int	format,	int mode, unsigned char	*data, int nelements);

       int XRotateWindowProperties(Display *display, Window w, Atom proper-
	      ties[], int num_prop, int	npositions);

       int XDeleteProperty(Display *display, Window w, Atom property);

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 prop-
		 erty if a partial read	was performed.

       data	 Specifies the property	data.

       delete	 Specifies a Boolean value that	determines whether the prop-
		 erty 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 cor-
		 rectly	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 XChange-
		 Property.

       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 PropMod-
		 eReplace, PropModePrepend, or PropModeAppend.

       nelements Specifies the number of elements of the specified data	for-
		 mat.

       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.

       prop_return
		 Returns the data in the specified format.  If the returned
		 format	is 8, the returned data	is represented as a char ar-
		 ray. If the returned format is	16, the	returned data is rep-
		 resented as a array of	short int type and should be cast to
		 that type to obtain the elements. If the returned format is
		 32, the property data will be stored as an array of longs
		 (which	in a 64-bit application	will be	64-bit values that are
		 padded	in the upper 4 bytes).

       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 applica-
		 tion 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 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:

       o    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 argu-
	    ment is ignored.

       o    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_re-
	    turn.  It also ignores the delete argument.	 The nitems_return ar-
	    gument is empty.

       o    If the specified property exists and either	you assign AnyProper-
	    tyType to the req_type argument or the specified type matches the
	    actual property type, XGetWindowProperty returns the actual	prop-
	    erty 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 (index-
	    ing	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 trail-
	    ing	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	er-
       rors.

       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:

       o    If mode is PropModeReplace,	XChangeProperty	discards the previous
	    property value and stores the new data.

       o    If mode is PropModePrepend or PropModeAppend, XChangeProperty in-
	    serts 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 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
       connection to the X server is closed, see section 2.6.  The maximum
       size of a property is server dependent and can vary dynamically depend-
       ing on the amount of memory the server has available.  (If there	is in-
       sufficient 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
       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(3), XInternAtom(3)
       Xlib - C	Language X Interface

X Version 11			 libX11	1.6.5		 XGetWindowProperty(3)

NAME | SYNTAX | ARGUMENTS | DESCRIPTION | DIAGNOSTICS | SEE ALSO

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