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 transferred 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 <!-- ##### STRUCT GdkAtom ##### -->
47 An opaque type representing a string as an index into a table
48 of strings on the X server.
52 <!-- ##### MACRO GDK_ATOM_TO_POINTER ##### -->
54 Converts a #GdkAtom into a pointer type.
60 <!-- ##### MACRO GDK_POINTER_TO_ATOM ##### -->
62 Extracts a #GdkAtom from a pointer. The #GdkAtom must have been
63 stored in the pointer with GDK_ATOM_TO_POINTER().
66 @ptr: a pointer containing a #GdkAtom.
69 <!-- ##### MACRO GDK_NONE ##### -->
71 A null value for #GdkAtom, used in a similar way as <literal>None</literal>
77 <!-- ##### FUNCTION gdk_text_property_to_text_list ##### -->
79 Converts a text string from the encoding as it is stored in
80 a property into an array of strings in the encoding of
81 the current local. (The elements of the array represent
82 the nul-separated elements of the original text string.)
85 @encoding: an atom representing the encoding. The most common
86 values for this are <literal>STRING</literal>,
87 or <literal>COMPOUND_TEXT</literal>. This is
88 value used as the type for the property.
89 @format: the format of the property.
91 @length: the length of the property, in items.
92 @list: location to store a terminated array of strings
93 in the encoding of the current locale. This
94 array should be freed using gdk_free_text_list().
95 @Returns: the number of strings stored in @list, or 0,
96 if the conversion failed.
99 <!-- ##### FUNCTION gdk_text_property_to_text_list_for_display ##### -->
113 <!-- ##### FUNCTION gdk_free_text_list ##### -->
115 Frees the array of strings created by
116 gdk_text_property_to_text_list().
119 @list: the value stored in the @list parameter by
120 a call to gdk_text_property_to_text_list().
123 <!-- ##### FUNCTION gdk_text_property_to_utf8_list ##### -->
136 <!-- ##### FUNCTION gdk_text_property_to_utf8_list_for_display ##### -->
150 <!-- ##### FUNCTION gdk_string_to_compound_text ##### -->
152 Converts a string from the encoding of the current locale
153 into a form suitable for storing in a window property.
156 @str: a nul-terminated string.
157 @encoding: location to store the encoding atom (to be used as the type for the property).
158 @format: location to store the format for the property.
159 @ctext: location to store newly allocated data for the property.
160 @length: location to store the length of @ctext in items.
161 @Returns: 0 upon sucess, non-zero upon failure.
164 <!-- ##### FUNCTION gdk_string_to_compound_text_for_display ##### -->
178 <!-- ##### FUNCTION gdk_free_compound_text ##### -->
180 Frees the data returned from gdk_string_to_compound_text().
183 @ctext: The pointer stored in @ctext from a call to gdk_string_to_compound_text().
186 <!-- ##### FUNCTION gdk_utf8_to_string_target ##### -->
195 <!-- ##### FUNCTION gdk_utf8_to_compound_text ##### -->
208 <!-- ##### FUNCTION gdk_utf8_to_compound_text_for_display ##### -->
222 <!-- ##### FUNCTION gdk_atom_intern ##### -->
224 Finds or creates an atom corresponding to a given string.
227 @atom_name: a string.
228 @only_if_exists: if %TRUE, GDK is allowed to not create a new atom, but
229 just return %GDK_NONE if the requested atom doesn't already
230 exists. Currently, the flag is ignored, since checking the
231 existance of an atom is as expensive as creating it.
232 @Returns: the atom corresponding to @atom_name.
235 <!-- ##### FUNCTION gdk_atom_name ##### -->
237 Determines the string corresponding to an atom.
241 @Returns: a newly-allocated string containing the string
242 corresponding to @atom. When you are done
243 with the return value, you should free it
247 <!-- ##### FUNCTION gdk_property_get ##### -->
249 Retrieves a portion of the contents of a property. If the
250 property does not exist, then the function returns %FALSE,
251 and %GDK_NONE will be stored in @actual_property_type.
255 The <function>XGetWindowProperty()</function>
256 function that gdk_property_get()
257 uses has a very confusing and complicated set of semantics.
258 Unfortunately, gdk_property_get() makes the situation
259 worse instead of better (the semantics should be considered
260 undefined), and also prints warnings to stderr in cases where it
261 should return a useful error to the program. You are advised to use
262 <function>XGetWindowProperty()</function>
263 directly until a replacement function for gdk_property_get()
268 @window: a #GdkWindow.
269 @property: the property to retrieve.
270 @type: the desired property type, or %GDK_NONE, if any type of data
271 is acceptable. If this does not match the actual
272 type, then @actual_format and @actual_length will
273 be filled in, a warning will be printed to stderr
274 and no data will be returned.
275 @offset: the offset into the property at which to begin
276 retrieving data. (in 4 byte units!)
277 @length: the length of the data to delete. (in bytes, but
278 the actual retrieved length will be the next
279 integer multiple multiple of four greater than
281 @pdelete: if %TRUE, delete the property after retrieving the
283 @actual_property_type: location to store the actual type of
285 @actual_format: location to store the actual format of the data.
286 @actual_length: location to store the length of the retrieved
288 @data: location to store a pointer to the data. The retrieved
289 data should be freed with g_free() when you are finished
291 @Returns: %TRUE if data was sucessfully received and stored
292 in @data, otherwise %FALSE.
295 <!-- ##### FUNCTION gdk_property_change ##### -->
297 Changes the contents of a property on a window.
300 @window: a #GdkWindow.
301 @property: the property to change.
302 @type: the new type for the property. If @mode is
303 %GDK_PROP_MODE_PREPEND or %GDK_PROP_MODE_APPEND, then this
304 must match the existing type or an error will occur.
305 @format: the new format for the property. If @mode is
306 %GDK_PROP_MODE_PREPEND or %GDK_PROP_MODE_APPEND, then this
307 must match the existing format or an error will occur.
308 @mode: a value describing how the new data is to be combined
309 with the current data.
311 (a <literal>guchar *</literal>
312 <literal>gushort *</literal>, or
313 <literal>gulong *</literal>, depending on @format), cast to a
314 <literal>guchar *</literal>.
315 @nelements: the number of elements of size determined by the format,
319 <!-- ##### ENUM GdkPropMode ##### -->
321 Describes how existing data is combined with new data when
322 using gdk_property_change().
325 @GDK_PROP_MODE_REPLACE: the new data replaces the existing data.
326 @GDK_PROP_MODE_PREPEND: the new data is prepended to the existing data.
327 @GDK_PROP_MODE_APPEND: the new data is appended to the existing data.
329 <!-- ##### FUNCTION gdk_property_delete ##### -->
331 Deletes a property from a window.
334 @window: a #GdkWindow.
335 @property: the property to delete.