XRC resources format specification
                      ==================================

                         !!!!! NOT YET FINISHED !!!!!

0. Introduction
---------------

This note describes the file format used for storing XRC resources that are
used by wxXmlResource class. It is probably only useful for those implementing
dialog editors with XRC support.

If you only want to use the resources, you can choose from a number of editors:
  a) wxDesigner (http://www.roebling.de)
  b) XRCed (wxPython/tools)
  c) wxWorkshop (http://wxworkshop.sf.net)
  b) wxrcedit (contrib/utils/wxrcedit)

The XRC format is based on XML 1.0 (please consult W3C's specification). There
is no DTD available since it is not possible to fully describe the format with
the limited expressive power of DTDs.


1. Terminology
--------------

The usual XML terminology applies. In particular, we shall use the terms 
"node", "property" and "value" in the XML sense:

    <node property1="value1" property2="value2">...</node>

The term "attribute" is specific to XRC and refers to a property-less subnode 
of an <object> or <object_ref> node. In the example bellow, <pos>, <label> and
<style> are attributes, while neither <resource> nor either of <object>s is:

    <?xml version="1.0" encoding="utf-8">
    <resource xmlns="http://www.wxwindows.org/wxxrc" version="2.3.0.1">
        <object class="wxPanel">
            <style>wxSUNKEN_BORDER</style>
            <object class="wxStaticText">
                <label>A label</label>
                <pos>10,10</pos>
            </object>
        </object>
    </resource>


2. Elementary description
-------------------------

XRC resource file is a well-formed XML 1.0 document. All elements of XRC file are
from the http://www.wxwindows.org/wxxrc namespace. 

The root node of XRC document must be <resource>. The <resource> node has 
optional "version" property. Default version  (in absence of the version 
property) is "0.0.0.0". The version consists of four integers separated by 
periods. Version of XRC format changes only if there was an incompatible 
change introduced (i.e. either the library cannot understand old resource 
files or older versions of the library wouldn't understand the new format).
The first three integers are major, minor and release number of the wxWindows 
release when the change was introduced, the last one is revision number and 
is 0 for the first incompatible change in given wxWindows release, 1 for 
the second etc.

Differences between versions are described within this document in paragraphs
entitled "Version Note".

The <resource> node contains namespace declaration, too:

    <resource xmlns="http://www.wxwindows.org/wxxrc" version="2.3.0.1">

The <resource> node is only allowed to have <object> and <object_ref>
subnodes, all of which must have the "name" property.

The <object> node represents a single object (GUI element) and it usually maps
directly to a wxWindows class instance. It three properties: "name", "class"
and "subclass". "class" must always be present, it tells XRC what wxWindows
object should be created in this place. The other two are optional. 
"name" is ID used to identify the object. It is the value passed to the XRCID() macro
and is also used to construct wxWindow's id and name attributes and must be unique
among all children of the neareset container object (wxDialog, wxFrame, wxPanel,
wxNotebook) upside from the object in XML nodes hiearchy (two distinct containers
may contain objects with same "name", though). "subclass" is
optional name of class whose constructor will be called instead of the constructor
for "class". Subclass must be available in the program that loads the resource,
must be derived from "class" and must be registered within wxWindows' RTTI system.

Example:

    <object name="MyList1" class="wxListCtrl" subclass="MyListCtrlClass">
        ...
    </object>    
    
<object> node may have arbitrary child nodes. What child nodes and their semantics
are class-dependent and are defined later in this document. The user is allowed
to register new object handlers within XRC and extend it to accept new <object>
classes (and therefore different <object>'s child nodes).

<object_ref> node is identical to <object>, except that it does _not_ have "class"
property and has additonal required property "ref". It's concept is similar to Unix
symlinks: value of the "ref" property is equal to the value of "name" property of
some existing node (called referred node) in the resources (not neccessary top-level). 
Referred node's "class" property and all subnodes are copied in place of the referee
<object_ref> node which is then processed as regular <object> node. If the <object_ref>
node itself has child nodes, then these nodes _override_ any nodes from the referred node.

Example:

    <object name="foo" class="wxTextCtrl">
        <value>hello</value>
        <size>100,-1d</size>
    </object>
    <object_ref name="bar" ref="foo">
        <value>bar</value>               <!-- override! -->
    </object>

is identical to:    

    <object name="foo" class="wxTextCtrl">
        <value>hello</value>
        <size>100,-1d</size>
    </object>
    <object name="bar" class="wxTextCtrl">
        <value>bar</value>
        <size>100,-1d</size>
    </object>


3. Common attributes
--------------------

TODO

4. Supported classes
--------------------

TODO

=== EOF ===

Version: $Id$