1 <!-- ##### SECTION Title ##### -->
4 <!-- ##### SECTION Short_Description ##### -->
5 functions to manipulate properties on windows.
7 <!-- ##### SECTION Long_Description ##### -->
9 Each window under X can have any number of associated
10 <firstterm>properties</firstterm> attached to it.
11 Properties are arbitrary chunks of data identified by
12 <firstterm>atom</firstterm>s. (An <firstterm>atom</firstterm>
13 is a numeric index into a string table on the X server. They are used
14 to transfer strings efficiently between clients without
15 having to transfer the entire string.) A property
16 has an associated type, which is also identified
20 A property has an associated <firstterm>format</firstterm>,
21 an integer describing how many bits are in each unit
22 of data inside the property. It must be 8, 16, or 32.
23 When data is transfered between the server and client,
24 if they are of different endianesses it will be byteswapped
25 as necessary according to the format of the property.
26 Note that on the client side, properties of format 32
27 will be stored with one unit per <emphasis>long</emphasis>,
28 even if a long integer has more than 32 bits on the platform.
29 (This decision was apparently made for Xlib to maintain
30 compatibility with programs that assumed longs were 32
31 bits, at the expense of programs that knew better.)
34 The functions in this section are used to add, remove
35 and change properties on windows, to convert atoms
36 to and from strings and to manipulate some types of
37 data commonly stored in X window properties.
40 <!-- ##### SECTION See_Also ##### -->
45 <!-- ##### TYPEDEF GdkAtom ##### -->
47 A numeric type representing a string as an index into a table
48 of strings on the X server.
52 <!-- ##### MACRO GDK_NONE ##### -->
59 <!-- ##### FUNCTION gdk_text_property_to_text_list ##### -->
61 Convert a text string from the encoding as it is stored in
62 a property into an array of strings in the encoding of
63 the current local. (The elements of the array represent
64 the null-separated elements of the original text string.)
67 @encoding: an atom representing the encoding. The most common
68 values for this are <literal>STRING</literal>,
69 or <literal>COMPOUND_TEXT</literal>. This is
70 value used as the type for the property.
71 @format: the format of the property.
73 @length: the length of the property, in item.s
74 @list: location to store a terminated array of strings
75 in the encoding of the current locale. This
76 array should be freed using gdk_free_text_list().
77 @Returns: the number of strings stored in @list, or 0,
78 if the conversion failed.
81 <!-- ##### FUNCTION gdk_free_text_list ##### -->
83 Free the array of strings created by
84 gdk_text_property_to_text_list().
87 @list: the value stored in the @list parameter by
88 a call to gdk_text_property_to_text_list().
91 <!-- ##### FUNCTION gdk_string_to_compound_text ##### -->
93 Convert a string from the encoding of the current locale
94 into a form suitable for storing in a window property.
97 @str: a null-terminated string.
98 @encoding: location to store the encoding atom (to be used as the type for the property).
99 @format: location to store the format for the property.
100 @ctext: location to store newly allocated data for the property.
101 @length: location to store the length of @ctext in items.
102 @Returns: 0 upon sucess, non-zero upon failure.
105 <!-- ##### FUNCTION gdk_free_compound_text ##### -->
107 Free the data returned from gdk_string_to_compound_text().
110 @ctext: The pointer stored in @ctext from a call to gdk_string_to_compound_text().
113 <!-- ##### FUNCTION gdk_atom_intern ##### -->
115 Find or create an atom corresponding to a given string.
118 @atom_name: a string.
119 @only_if_exists: if %TRUE, do not create a new atom, but
120 just return the atom if it already exists.
121 @Returns: the atom corresponding to @atom_name, or, if
122 @only_if_exists is false, and an atom does not
123 already exists for the string, %GDK_NONE.
126 <!-- ##### FUNCTION gdk_atom_name ##### -->
128 Determine the string corresponding to an atom.
132 @Returns: a newly allocated string containing the string
133 corresponding to @atom. When you are done
134 with the return value, you should free it
138 <!-- ##### FUNCTION gdk_property_get ##### -->
140 Retrieves a portion of the contents of a property. If the
141 property does not exist, then the function returns FALSE,
142 and %GDK_NONE will be stored in @actual_property_type.
144 Note: the <function>XGetWindowProperty()</function>
145 function that gdk_property_get()
146 uses has a very confusing and complicated set of semantics.
147 Unfortunately, gdk_property_get() makes the situation
148 worse instead of better (the semantics should be considered
149 undefined), and also prints warnings to stderr in cases where it
150 should return a useful error to the program. You are advised to use
151 <function>XGetWindowProperty()</function>
152 directly until a replacement function for gdk_property_get()
156 @window: a #GdkWindow.
157 @property: the property to retrieve.
158 @type: the desired property type, or 0, if any type of data
159 is acceptable. If this does not match the actual
160 type, then @actual_format and @actual_length will
161 be filled in, a warning will be printed to stderr
162 and no data will be returned.
163 @offset: the offset into the property at which to begin
164 retrieving data. (in 4 byte units!)
165 @length: the length of the data to delete. (in bytes, but
166 the actual retrieved length will be the next
167 integer multiple multiple of four greater than
169 @pdelete: if %TRUE, delete the property after retrieving the
171 @actual_property_type: location to store the actual type of
173 @actual_format: location to store the actual format of the data.
174 @actual_length: location to store the length of the retrieved
176 @data: location to store a pointer to the data. The retrieved
177 data should be freed with g_free() when you are finished
179 @Returns: %TRUE if data was sucessfully received and stored
180 in @data, otherwise %FALSE.
183 <!-- ##### FUNCTION gdk_property_change ##### -->
185 Change the contents of a property on a window.
188 @window: a #GdkWindow.
189 @property: the property to change.
190 @type: the new type for the property. If @mode is
191 %GDK_PROP_MODE_REPLACE or %GDK_PROP_MODE_APPEND, then this
192 must match the existing type or an error will occur.
193 @format: the new format for the property. If @mode is
194 %GDK_PROP_MODE_REPLACE or %GDK_PROP_MODE_APPEND, then this
195 must match the existing format or an error will occur.
196 @mode: a value describing how the new data is to be combined
197 with the current data.
199 (a <literal>guchar *</literal>
200 <literal>gushort *</literal>, or
201 <literal>gulong *</literal>, depending on @format), cast to a
202 <literal>guchar *</literal>.
203 @nelements: the number of elements of size determined by the format,
207 <!-- ##### ENUM GdkPropMode ##### -->
209 Describes how existing data is combined with new data when
210 using gdk_property_change().
213 @GDK_PROP_MODE_REPLACE: the new data replaces the existing data.
214 @GDK_PROP_MODE_PREPEND: the new data is prepended to the existing data.
215 @GDK_PROP_MODE_APPEND: the new data is appended to the existing data.
217 <!-- ##### FUNCTION gdk_property_delete ##### -->
219 Delete a property from a window.
222 @window: a #GdkWindow.
223 @property: the property to delete.