changed exceptions handling to work under wxGTK

[wxWidgets.git] / 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) DialogBlocks (wxPython/tools)

and others listed on the Resources section of the wxWidgets web
site.

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.


Note: see also http://ldaptool.sourceforge.net/XRCGuide/XRCGuideSingle/



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 below, <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.wxwidgets.org/wxxrc" version="2.5.3.0">
        <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.wxwidgets.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 wxWidgets 
release when the change was introduced, the last one is revision number and 
is 0 for the first incompatible change in given wxWidgets 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.wxwidgets.org/wxxrc" version="2.5.3.0">

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 wxWidgets class instance. It three properties: "name", "class"
and "subclass". "class" must always be present, it tells XRC what wxWidgets
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 nearest container object (wxDialog, wxFrame,
wxPanel, wxNotebook) upside from the object in XML nodes hierarchy (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
wxWidgets' 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 additional required property "ref". Its 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 necessary 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 wxWidgets)
    "__"   -> "_"
    "\n"   -> line break (C character '\n')
    "\r"   -> carriage return (C character '\r')
    "\t"   -> tab (C character '\t')
    "\\"   -> "\"
              (introduced in version 2.5.3.0, not done in earlier versions)

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 delimited with any combination of whitespaces
and '|'. Possible flags are class-dependent and are not described in this
technote. Please refer to wxWidgets manual for all styles that given class can
accept; if XRC does not accept a flag listed in wxWidgets 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, effectively 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 below). 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).


Font
----
Font value. A font can be described either in terms of its elementary
properties, or it can be derived from one of system fonts. The font node
may contain following subnodes (the table lists subnode name on the left and
variable type as per the definitions above on the right side):

size            UnsignedInteger
style           normal | italic | slant
weight          normal | bold | light
family          roman | script | decorative | swiss | modern | teletype
underlined      Boolean
face            comma-separated list of faces
encoding        charset of the font (meaningless in Unicode build), as string
sysfont         symbolic name of system standard font
                (one of wxSYS_*_FONT constants)
relativesize    Float, font size relative to choosen system font's size;
                can only be used when 'sysfont' is used and when 'size' is not
                used

All of them are optional, if they are missing, wxFont default is used.

Examples:
    
    <font>
        <face>arial,helvetica</face>
        <size>12</size>
    </font>
    
    <font>
        <sysfont>wxSYS_DEFAULT_GUI_FONT</sysfont>
        <weight>bold</weight>
        <relativesize>1.5</relativesize>
    </font>


Colour
------
A colour value is either explicit RGB value in the standard #rrggbb format
where rr, gg and bb are hexadecimal case-insensitive values in the 00..FF
range, or a symbolic name. Symbolic names are wxSYS_COLOUR_* constants defined
by wxWidgets, written as strings.

Example:

    <bg>wxSYS_COLOUR_SCROLLBAR</bg>
    <fg>#FF0000</fg>



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

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


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


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


wxCheckList
-----------
pos                        Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxCheckList]
content                    (see below)             (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>


wxDatePickerCtrl
----------------
pos                        Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxDatePickerCtrl]


wxDialog
--------
pos                        Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxDialog]         wxDEFAULT_DIALOG_STYLE
title                      I18nString              ""
icon                       Bitmap                  (empty)
centered                   Boolean                 false

wxDialog may have children objects.


wxFrame
--------
pos                        Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxDialog]         wxDEFAULT_FRAME_STYLE
title                      I18nString              ""
icon                       Bitmap                  (empty)
centered                   Boolean                 false

wxFrame may have children objects. There can be at most one wxToolBar,
wxMenuBar and wxStatusBar children; objects of these types are automatically
set as frame's tool-, menu- and statusbar respectively.


wxMDIParentFrame
----------------

Supports same attributes and children nodes as wxFrame. Additionally, children
may be of the wxMDIChildFrame type.


wxMDIChildFrame
---------------

Supports same attributes and children nodes as wxFrame.


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

wxScolledWindow may have children objects.


wxSplitterWindow
----------------
pos                        Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxSplitterWindow] wxSP_3D
sashpos                    Integer                 0
                           (Initial sash position)
minsize                    Integer                 -1
                           (Minimal panel size)
orientation                "horizontal"|"vertical" horizontal

wxSplitterWindow must have at least one and at most two children objects.
If there's only one child object, it is passed to wxSplitterWindow::Initialize
and the splitter is created unsplit. If there are two children, the
splitter is created split, either horizontally or vertically depending
on the value of "orientation" attribute.


wxStatusBar
-----------
fields                     Integer number of fields
widths                     Width1, Width2, Width3, ...


wxToolBar
---------
pos                        Position                -1,-1
size                       Size                    -1,-1
style                      Style[wxToolBar]        wxNO_BORDER|wxTB_HORIZONTAL
bitmapsize                 Size                    -1,-1
                           (Size of contained bitmaps)
margins                    Size                    -1,-1
packing                    Integer                 -1
separation                 Integer                 -1

wxToolBar node may have children <object> and <object_ref> nodes. Their class
may be either "tool", "separator" or any wxWidgets class derived from
wxControl. "tool" and "separator" are special pseudo-classes that may only
appear within wxToolBar node. Their attributes are as follows:

    separator
    ---------
    (doesn't have any attributes)

    tool
    ----
    bitmap                 Bitmap                  
    bitmap2                Bitmap                  wxNullBitmap
    toggle                 Boolean                 0
    radio                  Boolean                 0
    label                  I18nString              ""
    tooltip                I18nString              ""
    longhelp               I18nString              ""
    pos                    Position                -1,-1

    Constraints:
      At most one of "toggle" and "radio" attributes may be 1.
      Attribute "pos" may not appear if "label" or "radio" attributes
      are used or if parent wxToolBar's style contains wxTB_TEXT.
    
    Note:
      Use of "pos" attribute is strongly discouraged, it is deprecated
      usage of wxToolBar and it is not supported by MSW and GTK
      implementations.

Children objects are added to the toolbar using AddTool for "tool" class,
AddSeparator for "separator" and AddControl for other classes.



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

FIXME -- "platform" property handling


=== EOF ===

Version: $Id$