While Ion does not not have a truly object-oriented design 1, 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.
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.
For simplicity we consider only the essential-for-basic-configuration
Ioncore, mod_ionws and mod_query classes.
See Appendix for the full class hierachy visible
to Lua side.
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 1 lists out the Ion class hierarchy and below we explain what features of Ion the classes implement.
Obj |-->WRegion | |-->WClientWin | |-->WWindow | | |-->WRootWin | | |-->WMPlex | | | |-->WScreen | | | |-->WFrame | | |-->WInput (mod_query) | | |-->WEdln (mod_query) | | |-->WMessage (mod_query) | |-->WGenWS | |-->WIonWS (mod_ionws) |-->WSplit (mod_ionws) |
The core classes:
Classes implemented by the ionws module:
Classes implemented by the query module:
Each object of type WRegion has a parent and possibly a manager associated to it. The parent 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 2.
WRootWins |-->WScreens |-->WIonWSs |-->WClientWins in full screen mode |-->WFrames |-->WClientWins, including transients |-->a possible WEdln or WMessage |
WRegions have very little control over their children as a parent. The manager 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 3. 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.
WRootWins |-->WScreens |-->full screen WClientWins | |-->transient WClientWins (dialogs) |-->WIonWSs |-->WFrames |-->WClientWins | |-->transient WClientWins (dialogs) |-->possibly a WEdln or WMessage |
In the standard setup, keeping queries, messages and menus out of consideration: