Provided by: libx11-doc_1.6.9-2ubuntu1_all bug

NAME

       XGetWindowProperty,     XListProperties,     XChangeProperty,     XRotateWindowProperties,
       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_return);

       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 properties[],  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 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.

       prop_return
                 Returns  the  data  in  the  specified format.  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 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 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)
                 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 elements.  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 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.

       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.   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.

       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(3), XInternAtom(3)
       Xlib - C Language X Interface