wxWidgets/docs/tech/tn0014.txt

                      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 subnode 
of an <object> or <object_ref> node that is itself not <object> or <object_ref>. 
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>             <!-- attr -->
            <object class="wxStaticText">
                <label>A label</label>                 <!-- attr -->
                <pos>10,10</pos>                       <!-- attr -->
            </object>
        </object>
    </resource>

ATTRIBUTE VALUE is the content of all text elements within attribute tag. In the
above example, "wxSUNKEN_BORDER", "A label" and "10,10" are attribute values.
ATTRIBUTE TYPE defines what attribute values are valid for given attribute (you
can think of it as attribute value syntax definition).



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_ref>

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 attribute types
=========================

There are several attribute types (see section 1. Terminology) that are common
to many attributes of different classes:

String
------
Any text. Some characters have special interpretation and are translated
by XRC parser according to this table:
    "_"    -> "&"  ('&' is used to underline e.g. menu items in wxWindows)
    "__"   -> "_"
    "\n"   -> line break (C character '\n')
    "\r"   -> carriage return (C character '\r')
    "\t"   -> tabelator (C character '\t')

Version Note:
    '$' was used instead of '_' prior to version 2.3.0.1.


I18nString
----------
Like String, but the value is translated to native language using wxLocale
at runtime (unless it was disabled by not passing wxXRC_USE_LOCALE flag to
wxXmlResource constructor). Used for strings that are "visible" in the GUI.


UnsignedInteger
---------------
This is obvious. Only digits 0-9 may be present and there must be at least
one digit.


Integer
-------
Like UnsignedInteger but may be prefixed with '-' (ints less than zero).


Position
--------
Specifies (window's) position in 2D space. Syntax is <integer>,<integer>[d]
where <integer> is valid value of Integer type.


Size
----
Syntax is same as Position's syntax, but the values are interpreted as window
size (wxSize type) and not position (wxPosition type).


Style[wxSomeClass]
------------------
List of style flags that can be passed to wxSomeClass' constructor. Flags are
written in same way as in C++ code (e.g. "wxSUNKEN_BORDER", "wxHW_SCROLLBAR_NEVER")
and are delimined with any combination of whitespaces and '|'. Possible flags
are class-dependent and are not described in this technote. Please refer to wxWindows
manual for all styles that given class can accept; if XRC does not accept a flag
listed in wxWindows documentation, it is a bug.


Bitmap
------
Attribute value is interpreted as filename (either absolute or relative to
the location of XRC resource file). In addition, attribute node may have
"stock_id" and "stock_client" properties. Their values may be any of wxArtID (or
wxArtClient respectively) values as used by wxArtProvider (because the user may
define own constants, efectively any string is legal here). Examples are
"wxART_FILE_OPEN" (id) or "wxART_MENU" (client).

Any of "stock_id" or "stock_client" properties or the filename may be omitted. XRC
determines the bitmap to use according to this algorithm:
  1. If there is non-empty "stock_id" property, query wxArtProvider for the bitmap
     (if there is no "stock_client", use default one, which is usually wxART_OTHER;
     exceptions are noted in class-specific sections bellow). If the query fails,
     continue to 2.
  2. Load the bitmap from the file in attribute value.


Boolean
-------
Boolean value, either "0" (false) or "1" (true).



4. Supported classes
====================

Attributes are listed in tables in the following format:
attribute name             attribute type          default value, if any
                           [(optional remarks....................
                           ...................................)]

wxBitmap
--------
This is a special case, because it does not create a wxWindow instance but 
creates wxBitmap instead. Another exceptional thing is that it does not have
any attributes. Instead, the node itself is interpreted as if it were attribute
of type Bitmap.

Example: <object class="wxBitmap">bitmaps/foo.gif</object>


wxIcon
------
Identical to wxBitmap class, except that it creates wxIcon instead of wxBitmap.


wxButton
--------
position                   Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxButton]    

label                      I18nString
default                    Boolean                 false
                           (Is the button default button?)


wxCalendarCtrl
--------------
position                   Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxCalendarCtrl]


wxCheckBox
----------
position                   Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxCheckBox]
checked                    Boolean                 false


wxCheckList
-----------
position                   Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxCheckList]
content                    (see bellow)            (empty)

Optional "content" attribute does not have attribute value. Instead,
arbitrary number of <item> nodes may be rooted under it (the control
is filled with strings contained in these nodes). Each <item>
node must contain I18nString value and may have "checked" property
with possible values "0" or "1" indicating the the item is initially
checked.

Example:
<object class="wxCheckList">
    <content>
      <item>One</item>
      <item checked="1">Two</item>
      <item checked="1">Three</item>
      <item>Four</item>
    </content>
</object>


wxScrolledWindow
----------------
position                   Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxScrolledWindow] wxHSCROLL | wxVSCROLL



5. More features
================

FIXME -- "platform" property handling


=== EOF ===

Version: $Id$