XGetWindowProperty, XListProperties, XChangeProperty, XRo-
       tateWindowProperties, 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;


ARGUMENTS

       actual_format_return
                 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 infor-
                 mation allows the X server to correctly perform
                 byte-swap operations as necessary.  If the for-
                 mat 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 speci-
                 fied 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.

       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.

       a pointer to the data actually returned.  XGetWindowProp-
       erty 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_for-
            mat_return and bytes_after_return.  The nitems_return
            argument is empty.  In this case, the delete argument
            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_return.  It also ignores the
            delete argument.  The nitems_return argument is
            empty.

       o    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 trail-
            ing unread bytes in the stored property.

       If the returned format is 8, the returned data is repre-
       sented 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

       The XListProperties function returns a pointer to an array
       of atom properties that are defined for the specified win-
       dow 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 per-
       forms 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 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 avail-
       able.  (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 prop-
       erties 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
       window and causes the X server to generate a PropertyNo-
       tify 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 spe-
                 cific 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



X Version 11               Release 6.4                          1