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-<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></A>
-
-<UL CLASS="ChildLinks">
-<LI><A NAME="tex2html269"
- HREF="node3.html#SECTION00310000000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN> Modules</A>
-<LI><A NAME="tex2html270"
- HREF="node3.html#SECTION00320000000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN> Class and object hierarchies</A>
-<UL>
-<LI><A NAME="tex2html271"
- HREF="node3.html#SECTION00321000000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN> Class hierarchy</A>
-<LI><A NAME="tex2html272"
- HREF="node3.html#SECTION00322000000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN> Object hierarchies: WRegion parents and managers</A>
-<UL>
-<LI><A NAME="tex2html273"
- HREF="node3.html#SECTION00322100000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN> Parent-child relations</A>
-<LI><A NAME="tex2html274"
- HREF="node3.html#SECTION00322200000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN> Manager-managed relations</A>
-</UL>
-<LI><A NAME="tex2html275"
- HREF="node3.html#SECTION00323000000000000000"><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">3</SPAN> Summary</A>
-</UL></UL>
-<!--End of Table of Child-Links-->
-<HR>
-
-<H1><A NAME="SECTION00300000000000000000"></A>
-<A NAME="chap:prelim"></A>
-<BR>
-<SPAN CLASS="arabic">2</SPAN>. Preliminaries: Key concepts and relations
-</H1>
-
-<P>
-The purpose of this chapter to explain some of key concepts and
-relations you need to understand before reading the following
-chapters. These include modules explained in section <A HREF="#sec:modules">2.1</A>
-and the Ion class and object hierarchies, section <A HREF="#sec:objects">2.2</A>.
-
-<P>
-
-<H2><A NAME="SECTION00310000000000000000"></A>
-<A NAME="sec:modules"></A>
-<BR>
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN> Modules
-</H2>
-
-<P>
-Ion has been designed so that the 'ion' executable only implements some
-basic services on top of which very different kinds of window managers
-could be build by loading the appropriate 'modules'. On modern system
-these modules are simply dynamically loaded <SPAN CLASS="textit">.so</SPAN> libraries. On
-more primitive systems, or if you want to squeeze total size of the
-executable and libraries, the modules can optionally be statically
-linked to the main binary, but must nevertheless be loaded with the
-<A HREF="#fn:dopath"><TT>dopath</TT></A> function. Modules may also include Lua code.
-
-<P>
-If no modules are loaded, all client windows appear in full screen mode.
-To get better window management support, one or more workspace modules
-should be loaded. Currently Ion provides the following modules:
-
-<P>
-<DL>
-<DT><STRONG><SPAN CLASS="textit">mod_tiling</SPAN></STRONG></DT>
-<DD>Tilings for workspaces of the original tiled
- Ion kind.
-
-</DD>
-<DT><STRONG><SPAN CLASS="textit">mod_query</SPAN></STRONG></DT>
-<DD>Queries (for starting programs and so on)
- and message boxes.
-
-</DD>
-<DT><STRONG><SPAN CLASS="textit">mod_menu</SPAN></STRONG></DT>
-<DD>Support for menus, both pull-down and
- keyboard-operated in-frame menus.
-
-</DD>
-<DT><STRONG><SPAN CLASS="textit">mod_statusbar</SPAN></STRONG></DT>
-<DD>Module that implements a statusbar that
- can be adaptively embedded in each workspace's layout.
-
-</DD>
-<DT><STRONG><SPAN CLASS="textit">mod_dock</SPAN></STRONG></DT>
-<DD>Module for docking Window Maker dock-apps.
- The dock can both float and be embedded as the statusbar.
-
-</DD>
-<DT><STRONG><SPAN CLASS="textit">mod_sp</SPAN></STRONG></DT>
-<DD>This module implements a scratchpad frame that can
- be toggled on/off everywhere. Think of the 'console' in some
- first-person shooters.
-
-</DD>
-<DT><STRONG><SPAN CLASS="textit">mod_sm</SPAN></STRONG></DT>
-<DD>Session management support module.
- <SPAN CLASS="textit">Loaded automatically when needed!</SPAN>
-</DD>
-</DL>
-
-<P>
-So-called drawing engines are also implemented as a modules,
-but they are not discussed here; see chapter <A HREF="node5.html#chap:gr">4</A>.
-
-<P>
-The stock configuration for the <SPAN CLASS="textit">ion3</SPAN> executable loads all of the
-modules mentioned above except <SPAN CLASS="textit">mod_dock</SPAN>.
-The stock configuration for the <SPAN CLASS="textit">pwm3</SPAN> executable (which differs
-from the <SPAN CLASS="textit">ion3</SPAN> executable in a few configuration details)
-loads another set of modules.
-
-<P>
-
-<P>
-
-<H2><A NAME="SECTION00320000000000000000"></A>
-<A NAME="sec:objects"></A>
-<BR>
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN> Class and object hierarchies
-</H2>
-
-<P>
-While Ion does not not have a truly object-oriented design
-<A NAME="tex2html3"
- HREF="#foot297"><SUP><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN></SUP></A>,
-things that appear on the computer screen are, however, quite
-naturally expressed as such ``objects''. Therefore Ion implements
-a rather primitive OO system for these screen objects and some
-other things.
-
-<P>
-It is essential for the module writer to learn this object
-system, but also people who write their own binding configuration files
-necessarily come into contact with the class and object hierarchies
-- you need to know which binding setup routines apply where,
-and what functions can be used as handlers in which bindings.
-It is the purpose of this section to attempt to explain these
-hierarchies. If you do not wish the read the full section, at least
-read the summary at the end of it, so that you understand the very
-basic relations.
-
-<P>
-For simplicity we consider only the essential-for-basic-configuration
-Ioncore, <SPAN CLASS="textit">mod_tiling</SPAN> and <SPAN CLASS="textit">mod_query</SPAN> classes.
-See Appendix <A HREF="node9.html#app:fullhierarchy">B</A> for the full class hierarchy visible
-to Lua side.
-
-<P>
-
-<H3><A NAME="SECTION00321000000000000000">
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN> Class hierarchy</A>
-</H3>
-
-<P>
-One of the most important principles of object-oriented design methodology
-is inheritance; roughly how classes (objects are instances of classes)
-extend on others' features. Inheritance gives rise to class hierarchy.
-In the case of single-inheritance this hierarchy can be expressed as a
-tree where the class at the root is inherited by all others below it
-and so on. Figure <A HREF="#fig:classhierarchy">2.1</A> lists out the Ion class
-hierarchy and below we explain what features of Ion the classes
-implement.
-
-<P>
-
-<DIV ALIGN="CENTER"><A NAME="fig:classhierarchy"></A><A NAME="404"></A>
-<TABLE>
-<CAPTION ALIGN="BOTTOM"><STRONG>Figure 2.1:</STRONG>
-Partial Ioncore, <SPAN CLASS="textit">mod_tiling</SPAN> and <SPAN CLASS="textit">mod_query</SPAN>
- class hierarchy.</CAPTION>
-<TR><TD><PRE>
- Obj
- |-->WRegion
- | |-->WClientWin
- | |-->WWindow
- | | |-->WMPlex
- | | | |-->WFrame
- | | | |-->WScreen
- | | | |-->WRootWin
- | | |-->WInput (mod_query)
- | | |-->WEdln (mod_query)
- | | |-->WMessage (mod_query)
- | |-->WGroup
- | | |-->WGroupWS
- | | |-->WGroupCW
- | |-->WTiling (mod_tiling)
- |-->WSplit (mod_tiling)
-</PRE></TD></TR>
-</TABLE>
-</DIV>
-
-<P>
-The core classes:
-
-<P>
-<DL>
-<DT><STRONG>Obj</STRONG></DT>
-<DD><A NAME="410"></A>
- Is the base of Ion's object system.
-
-<P>
-</DD>
-<DT><STRONG>WRegion</STRONG></DT>
-<DD><A NAME="411"></A>
- is the base class for everything corresponding to something on the
- screen. Each object of type WRegion has a size and position
- relative to the parent WRegion. While a big part of Ion
- operates on these instead of more specialised classes, WRegion
- is a ``virtual'' base class in that there are no objects of ``pure''
- type WRegion; all concrete regions are objects of some class
- that inherits WRegion.
-
-<P>
-</DD>
-<DT><STRONG>WClientWin</STRONG></DT>
-<DD><A NAME="412"></A> is a class for
- client window objects, the objects that window managers are
- supposed to manage.
-
-<P>
-</DD>
-<DT><STRONG>WWindow</STRONG></DT>
-<DD><A NAME="413"></A> is the base class for all
- internal objects having an X window associated to them
- (WClientWins also have X windows associated to them).
-
-<P>
-</DD>
-<DT><STRONG>WMPlex</STRONG></DT>
-<DD>is a base class for all regions that ``multiplex''
- other regions. This means that of the regions managed by the multiplexer,
- only one can be displayed at a time.
-
-<P>
-</DD>
-<DT><STRONG>WScreen</STRONG></DT>
-<DD><A NAME="414"></A> is an instance of WMPlex
- for screens.
-
-<P>
-</DD>
-<DT><STRONG>WRootWin</STRONG></DT>
-<DD><A NAME="415"></A> is the class for
- root windows<A NAME="331"></A> of X screens<A NAME="332"></A>.
- It is an instance of WScreen.
- Note that an ``X screen'' or root window is not necessarily a
- single physical screen<A NAME="334"></A> as a root window
- may be split over multiple screens when ugly hacks such as
- Xinerama<A NAME="335"></A> are used. (Actually there can be only
- one root window when Xinerama is used.)
-
-<P>
-</DD>
-<DT><STRONG>WFrame</STRONG></DT>
-<DD><A NAME="416"></A> is the class for frames.
- While most Ion's objects have no graphical presentation, frames
- basically add to WMPlexes the decorations around client
- windows (borders, tabs).
-
-<P>
-</DD>
-<DT><STRONG>WGroup</STRONG></DT>
-<DD><A NAME="417"></A> is the base class for groups.
- Particular types of groups are workspaces
- (WGroupWS<A NAME="418"></A>)
- and groups of client windows
- (WGroupCW<A NAME="419"></A>).
-</DD>
-</DL>
-
-<P>
-Classes implemented by the <SPAN CLASS="textit">mod_tiling</SPAN> module:
-
-<P>
-<DL>
-<DT><STRONG>WTiling</STRONG></DT>
-<DD><A NAME="421"></A> is the class for tilings
- of frames.
-
-</DD>
-<DT><STRONG>WSplit</STRONG></DT>
-<DD><A NAME="422"></A> (or, more specifically, classes
- that inherit it) encode the WTiling tree structure.
-</DD>
-</DL>
-
-<P>
-Classes implemented by the <SPAN CLASS="textit">mod_query</SPAN> module:
-
-<P>
-<DL>
-<DT><STRONG>WInput</STRONG></DT>
-<DD><A NAME="424"></A> is a virtual base class for the
- two classes below.
-
-</DD>
-<DT><STRONG>WEdln</STRONG></DT>
-<DD><A NAME="425"></A> is the class for the ``queries'',
- the text inputs that usually appear at bottoms of frames and sometimes
- screens. Queries are the functional equivalent of ``mini buffers'' in
- many text editors.
-
-</DD>
-<DT><STRONG>WMessage</STRONG></DT>
-<DD><A NAME="426"></A> implements the boxes for
- warning and other messages that Ion may wish to display to the user.
- These also usually appear at bottoms of frames.
-</DD>
-</DL>
-
-<P>
-There are also some other ``proxy'' classes that do not refer
-to objects on the screen. The only important one of these for
-basic configuration is WMoveresMode that is used for
-binding callbacks in the move and resize mode.
-
-<P>
-
-<H3><A NAME="SECTION00322000000000000000">
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN> Object hierarchies: WRegion parents and managers</A>
-</H3>
-
-<P>
-
-<H4><A NAME="SECTION00322100000000000000">
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN> Parent-child relations</A>
-</H4>
-Each object of type WRegion has a parent and possibly a manager
-associated to it. The parent<A NAME="367"></A> for an object is always a
-WWindow and for WRegion with an X window (WClientWin,
-WWindow) the parent WWindow is given by the same relation of
-the X windows. For other WRegions the relation is not as clear.
-There is generally very few restrictions other than the above on the
-parent--child relation but the most common is as described in
-Figure <A HREF="#fig:parentship">2.2</A>.
-
-<P>
-
-<DIV ALIGN="CENTER"><A NAME="fig:parentship"></A><A NAME="378"></A>
-<TABLE>
-<CAPTION ALIGN="BOTTOM"><STRONG>Figure 2.2:</STRONG>
-Most common parent-child relations</CAPTION>
-<TR><TD><PRE>
- WRootWins
- |-->WScreens
- |-->WGroupWSs
- |-->WTilings
- |-->WClientWins in full screen mode
- |-->WFrames
- |-->WGroupCWs
- |-->WClientWins
- |-->WFrames for transients
- |-->a possible WEdln or WMessage
-</PRE></TD></TR>
-</TABLE>
-</DIV>
-
-<P>
-WRegions have very little control over their children as a parent.
-The manager<A NAME="382"></A> WRegion has much more control over its
-managed WRegions. Managers, for example, handle resize requests,
-focusing and displaying of the managed regions. Indeed the manager--managed
-relationship gives a better picture of the logical ordering of objects on
-the screen. Again, there are generally few limits, but the most common
-hierarchy is given in Figure <A HREF="#fig:managership">2.3</A>. Note that sometimes
-the parent and manager are the same object and not all objects may have
-a manager (e.g. the dock in the dock module at the time of writing this)
-but all have a parent-a screen if not anything else.
-
-<P>
-
-<H4><A NAME="SECTION00322200000000000000">
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN> Manager-managed relations</A>
-</H4>
-
-<P>
-
-<DIV ALIGN="CENTER"><A NAME="fig:managership"></A><A NAME="390"></A>
-<TABLE>
-<CAPTION ALIGN="BOTTOM"><STRONG>Figure 2.3:</STRONG>
-Most common manager-managed relations</CAPTION>
-<TR><TD><PRE>
- WRootWins
- |-->WScreens
- |-->WGroupCWs for full screen WClientWins
- | |-->WClientWins
- | |-->WFrames for transients (dialogs)
- | |--> WClientWin
- |-->WGroupWSs for workspaces
- | |-->WTiling
- | | |-->WFrames
- | | | |-->WGroupCWs (with contents as above)
- | | |-->possibly a WStatusBar or WDock
- | |-->WFrames for floating content
- | |-->possibly a WEdln, WMessage or WMenu
- | |-->possibly a WStatusBar or WDock (if no tiling)
- |-->WFrames for sticky stuff, such as the scratchpad
-</PRE></TD></TR>
-</TABLE>
-</DIV>
-
-<P>
-Note that a workspace can manage another workspace. This can be
-achieved with the <A HREF="#fn:attach_new"><TT>attach_new</TT></A> function, and allows you to nest
-workspaces as deep as you want.
-
-<P>
-
-<H3><A NAME="SECTION00323000000000000000">
-<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">3</SPAN> Summary</A>
-</H3>
-
-<P>
-In the standard setup, keeping queries, messages and menus out of
-consideration:
-
-<P>
-
-<UL>
-<LI>The top-level objects that matter are screens and they correspond
- to physical screens. The class for screens is WScreen.
-</LI>
-<LI>Screens contain (multiplex) groups (WGroup) and other
- objects, such as WFrames. Some of these are mutually exclusive
- to be viewed at a time.
-</LI>
-<LI>Groups of the specific kind WGroupWS often contain a
- WTiling tiling for tiling frames (WFrame), but
- groups may also directly contain floating frames.
-</LI>
-<LI>Frames are the objects with decorations such as tabs and borders.
- Frames contain (multiplex) among others (groups of) client windows,
- to each of which corresponds a tab in the frame's decoration. Only
- one client window (or other object) can be shown at a time in each
- frame. The class for client windows is WClientWin.
-</LI>
-</UL>
-
-<P>
-<BR><HR><H4>Footnotes</H4>
-<DL>
-<DT><A NAME="foot297">... design</A><A
- HREF="node3.html#tex2html3"><SUP><SPAN CLASS="arabic">2</SPAN>.<SPAN CLASS="arabic">1</SPAN></SUP></A></DT>
-<DD>the author doesn't like such artificial designs
-
-</DD>
-</DL>
-<DIV CLASS="navigation"><HR>
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