1XGetWindowProperty(3)           XLIB FUNCTIONS           XGetWindowProperty(3)
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NAME

6       XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindow‐
7       Properties, XDeleteProperty - obtain and change window properties
8

SYNTAX

10       int XGetWindowProperty(Display *display, Window w, Atom property, long
11              long_offset, long long_length, Bool delete, Atom req_type, Atom
12              *actual_type_return, int *actual_format_return, unsigned long
13              *nitems_return, unsigned long *bytes_after_return, unsigned char
14              **prop_return);
15
16       Atom *XListProperties(Display *display, Window w, int
17              *num_prop_return);
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19       int XChangeProperty(Display *display, Window w, Atom property, Atom
20              type, int format, int mode, unsigned char *data, int nelements);
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22       int XRotateWindowProperties(Display *display, Window w, Atom proper‐
23              ties[], int num_prop, int npositions);
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25       int XDeleteProperty(Display *display, Window w, Atom property);
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ARGUMENTS

28       actual_format_return
29                 Returns the actual format of the property.
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31       actual_type_return
32                 Returns the atom identifier  that defines the actual type of
33                 the property.
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35       bytes_after_return
36                 Returns the number of bytes remaining to be read in the prop‐
37                 erty if a partial read was performed.
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39       data      Specifies the property data.
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41       delete    Specifies a Boolean value that determines whether the prop‐
42                 erty is deleted.
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44       display   Specifies the connection to the X server.
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46       format    Specifies whether the data should be viewed as a list of
47                 8-bit, 16-bit, or 32-bit quantities.  Possible values are 8,
48                 16, and 32.  This information allows the X server to cor‐
49                 rectly perform byte-swap operations as necessary.  If the
50                 format is 16-bit or 32-bit, you must explicitly cast your
51                 data pointer to an (unsigned char *) in the call to XChange‐
52                 Property.
53
54       long_length
55                 Specifies the length in 32-bit multiples of the data to be
56                 retrieved.
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58       long_offset
59                 Specifies the offset in the specified property (in 32-bit
60                 quantities) where the data is to be retrieved.
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62       mode      Specifies the mode of the operation.  You can pass PropMod‐
63                 eReplace, PropModePrepend, or PropModeAppend.
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65       nelements Specifies the number of elements of the specified data for‐
66                 mat.
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68       nitems_return
69                 Returns the actual number of 8-bit, 16-bit, or 32-bit items
70                 stored in the prop_return data.
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72       num_prop  Specifies the length of the properties array.
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74       num_prop_return
75                 Returns the length of the properties array.
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77       npositions
78                 Specifies the rotation amount.
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80       prop_return
81                 Returns the data in the specified format.  If the returned
82                 format is 8, the returned data is represented as a char
83                 array. If the returned format is 16, the returned data is
84                 represented as a array of short int type and should be cast
85                 to that type to obtain the elements. If the returned format
86                 is 32, the property data will be stored as an array of longs
87                 (which in a 64-bit application will be 64-bit values that are
88                 padded in the upper 4 bytes).
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90       property  Specifies the property name.
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92       properties
93                 Specifies the array of properties that are to be rotated.
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95       req_type  Specifies the atom identifier associated with the property
96                 type or AnyPropertyType.
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98       type      Specifies the type of the property.  The X server does not
99                 interpret the type but simply passes it back to an applica‐
100                 tion that later calls XGetWindowProperty.
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102       w         Specifies the window whose property you want to obtain,
103                 change, rotate or delete.
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DESCRIPTION

106       The XGetWindowProperty function returns the actual type of the prop‐
107       erty; the actual format of the property; the number of 8-bit, 16-bit,
108       or 32-bit items transferred; the number of bytes remaining to be read
109       in the property; and a pointer to the data actually returned.  XGetWin‐
110       dowProperty sets the return arguments as follows:
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112       ·    If the specified property does not exist for the specified window,
113            XGetWindowProperty returns None to actual_type_return and the
114            value zero to actual_format_return and bytes_after_return.  The
115            nitems_return argument is empty.  In this case, the delete argu‐
116            ment is ignored.
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118       ·    If the specified property exists but its type does not match the
119            specified type, XGetWindowProperty returns the actual property
120            type to actual_type_return, the actual property format (never
121            zero) to actual_format_return, and the property length in bytes
122            (even if the actual_format_return is 16 or 32) to
123            bytes_after_return.  It also ignores the delete argument.  The
124            nitems_return argument is empty.
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126       ·    If the specified property exists and either you assign AnyProper‐
127            tyType to the req_type argument or the specified type matches the
128            actual property type, XGetWindowProperty returns the actual prop‐
129            erty type to actual_type_return and the actual property format
130            (never zero) to actual_format_return.  It also returns a value to
131            bytes_after_return and nitems_return, by defining the following
132            values:
133
134                 N = actual length of the stored property in bytes
135                      (even if the format is 16 or 32)
136                 I = 4 * long_offset
137                 T = N - I
138                 L = MINIMUM(T, 4 * long_length)
139                 A = N - (I + L)
140
141            The returned value starts at byte index I in the property (index‐
142            ing from zero), and its length in bytes is L.  If the value for
143            long_offset causes L to be negative, a BadValue error results.
144            The value of bytes_after_return is A, giving the number of trail‐
145            ing unread bytes in the stored property.
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147       If the returned format is 8, the returned data is represented as a char
148       array.  If the returned format is 16, the returned data is represented
149       as a short array and should be cast to that type to obtain the ele‐
150       ments.  If the returned format is 32, the returned data is represented
151       as a long array and should be cast to that type to obtain the elements.
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153       XGetWindowProperty always allocates one extra byte in prop_return (even
154       if the property is zero length) and sets it to zero so that simple
155       properties consisting of characters do not have to be copied into yet
156       another string before use.
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158       If delete is True and bytes_after_return is zero, XGetWindowProperty
159       deletes the property from the window and generates a PropertyNotify
160       event on the window.
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162       The function returns Success if it executes successfully.  To free the
163       resulting data, use XFree.
164
165       XGetWindowProperty can generate BadAtom, BadValue, and BadWindow
166       errors.
167
168       The XListProperties function returns a pointer to an array of atom
169       properties that are defined for the specified window or returns NULL if
170       no properties were found.  To free the memory allocated by this func‐
171       tion, use XFree.
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173       XListProperties can generate a BadWindow error.
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175       The XChangeProperty function alters the property for the specified win‐
176       dow and causes the X server to generate a PropertyNotify event on that
177       window.  XChangeProperty performs the following:
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179       ·    If mode is PropModeReplace, XChangeProperty discards the previous
180            property value and stores the new data.
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182       ·    If mode is PropModePrepend or PropModeAppend, XChangeProperty
183            inserts the specified data before the beginning of the existing
184            data or onto the end of the existing data, respectively.  The type
185            and format must match the existing property value, or a BadMatch
186            error results.  If the property is undefined, it is treated as
187            defined with the correct type and format with zero-length data.
188
189       If the specified format is 8, the property data must be a char array.
190       If the specified format is 16, the property data must be a short array.
191       If the specified format is 32, the property data must be a long array.
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193       The lifetime of a property is not tied to the storing client.  Proper‐
194       ties remain until explicitly deleted, until the window is destroyed, or
195       until the server resets.  For a discussion of what happens when the
196       connection to the X server is closed, see section 2.6.  The maximum
197       size of a property is server dependent and can vary dynamically depend‐
198       ing on the amount of memory the server has available.  (If there is
199       insufficient space, a BadAlloc error results.)
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201       XChangeProperty can generate BadAlloc, BadAtom, BadMatch, BadValue, and
202       BadWindow errors.
203
204       The XRotateWindowProperties function allows you to rotate properties on
205       a window and causes the X server to generate PropertyNotify events.  If
206       the property names in the properties array are viewed as being numbered
207       starting from zero and if there are num_prop property names in the
208       list, then the value associated with property name I becomes the value
209       associated with property name (I + npositions) mod N for all I from
210       zero to N - 1.  The effect is to rotate the states by npositions places
211       around the virtual ring of property names (right for positive nposi‐
212       tions, left for negative npositions).  If npositions mod N is nonzero,
213       the X server generates a PropertyNotify event for each property in the
214       order that they are listed in the array.  If an atom occurs more than
215       once in the list or no property with that name is defined for the win‐
216       dow, a BadMatch error results.  If a BadAtom or BadMatch error results,
217       no properties are changed.
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219       XRotateWindowProperties can generate BadAtom, BadMatch, and BadWindow
220       errors.
221
222       The XDeleteProperty function deletes the specified property only if the
223       property was defined on the specified window and causes the X server to
224       generate a PropertyNotify event on the window unless the property does
225       not exist.
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227       XDeleteProperty can generate BadAtom and BadWindow errors.
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DIAGNOSTICS

230       BadAlloc  The server failed to allocate the requested resource or
231                 server memory.
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233       BadAtom   A value for an Atom argument does not name a defined Atom.
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235       BadValue  Some numeric value falls outside the range of values accepted
236                 by the request.  Unless a specific range is specified for an
237                 argument, the full range defined by the argument's type is
238                 accepted.  Any argument defined as a set of alternatives can
239                 generate this error.
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241       BadWindow A value for a Window argument does not name a defined Window.
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SEE ALSO

244       XFree(3), XInternAtom(3)
245       Xlib - C Language X Interface
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249X Version 11                     libX11 1.3.4            XGetWindowProperty(3)
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