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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_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 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
                 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 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_return.  It also ignores  the  delete  argument.   The
            nitems_return argument 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
       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:

       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.  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
       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 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 1.6.9            XGetWindowProperty(3)

xorg-libX11 1.6.9 - Generated Fri Oct 25 15:39:10 CDT 2019
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