1XGetWindowProperty(3) XLIB FUNCTIONS XGetWindowProperty(3)
2
6 XGetWindowProperty, XListProperties, XChangeProperty, XRotateWindow‐
7 Properties, XDeleteProperty - obtain and change window properties
8
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 Atom *XListProperties(Display *display, Window w, int
17 *num_prop_return);
18 int XChangeProperty(Display *display, Window w, Atom property, Atom
20 type, int format, int mode, unsigned char *data, int nelements);
21 int XRotateWindowProperties(Display *display, Window w, Atom proper‐
23 ties[], int num_prop, int npositions);
24 int XDeleteProperty(Display *display, Window w, Atom property);
26
28 actual_format_return
29 Returns the actual format of the property.
30 actual_type_return
32 Returns the atom identifier that defines the actual type of
33 the property.
34 bytes_after_return
36 Returns the number of bytes remaining to be read in the prop‐
37 erty if a partial read was performed.
38 data Specifies the property data.
40 delete Specifies a Boolean value that determines whether the prop‐
42 erty is deleted.
43 display Specifies the connection to the X server.
45 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 long_length
55 Specifies the length in 32-bit multiples of the data to be
56 retrieved.
57 long_offset
59 Specifies the offset in the specified property (in 32-bit
60 quantities) where the data is to be retrieved.
61 mode Specifies the mode of the operation. You can pass PropMod‐
63 eReplace, PropModePrepend, or PropModeAppend.
64 nelements Specifies the number of elements of the specified data for‐
66 mat.
67 nitems_return
69 Returns the actual number of 8-bit, 16-bit, or 32-bit items
70 stored in the prop_return data.
71 num_prop Specifies the length of the properties array.
73 num_prop_return
75 Returns the length of the properties array.
76 npositions
78 Specifies the rotation amount.
79 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).
89 property Specifies the property name.
91 properties
93 Specifies the array of properties that are to be rotated.
94 req_type Specifies the atom identifier associated with the property
96 type or AnyPropertyType.
97 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.
101 w Specifies the window whose property you want to obtain,
103 change, rotate or delete.
104
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:
111 · 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.
117 · 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.
125 · 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 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 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.
146 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.
152 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.
157 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.
161 The function returns Success if it executes successfully. To free the
163 resulting data, use XFree.
164 XGetWindowProperty can generate BadAtom, BadValue, and BadWindow
166 errors.
167 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.
172 XListProperties can generate a BadWindow error.
174 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:
178 · If mode is PropModeReplace, XChangeProperty discards the previous
180 property value and stores the new data.
181 · 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 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.
192 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.)
200 XChangeProperty can generate BadAlloc, BadAtom, BadMatch, BadValue, and
202 BadWindow errors.
203 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.
218 XRotateWindowProperties can generate BadAtom, BadMatch, and BadWindow
220 errors.
221 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.
226 XDeleteProperty can generate BadAtom and BadWindow errors.
228
230 BadAlloc The server failed to allocate the requested resource or
231 server memory.
232 BadAtom A value for an Atom argument does not name a defined Atom.
234 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.
240 BadWindow A value for a Window argument does not name a defined Window.
242
244 XFree(3), XInternAtom(3)
245 Xlib - C Language X Interface
246X Version 11 libX11 1.6.5 XGetWindowProperty(3)