The most important &xwp; class replacements are:

1. XFolder for regular folders, which contains the main functionality of &xwp;,
   
2. XFldDisk for "disk" objects, which appear in the "Drives" folder,
   
3. XFldObject, the WPS root class, for being able to access a whole number of WPS internals, and
   
4. XFldDesktop for the new Desktop features, especially the eXtended Shutdown procedure.

In the sense described on the previous page, the XFolder class is a descendant of the WPFolder class. This way, it can do everything that a regular folder can. As a new function, it adds new context menu items to all folders, allows for folder hotkeys, changes the folder window titles, etc.

By using polymorphism, XFolder redefines certain WPFolder methods, as described below.

However, XFolder is then registered with the WPS as a WPFolder replacement, meaning that the WPS will use the XFolder class as its standard folder class, instead of WPFolder. In doing so, the WPFolder class is not any more used directly, but only through its replacement (and descendant) class, XFolder.

Some of the WPFolder methods that the XFolder class overrides are (this will probably only of interest for programmers):

• wpModifyPopupMenu: This WPObject method is called by the WPS just before an object's context menu is displayed. Each WPS class adds its own, class-specific menu items here.

  Since XFolder plays with menus a lot, this is one of the most important methods which XFolder overrides. In this method, XFolder first calls the parent class's (WPFolder's) wpModifyPopupMenu to have all the standard menu items added to the object's context menu.

  It then searches for the XFolder configuration folder (which must have the object ID <XFOLDER_CONFIG>) and populates it invisibly. Now it goes through all objects in here, adding submenus and menu items to the context menu accordingly. If the configuration folder is not found, a message box pops up and an empty folder with the aforementioned ID is created on the desktop.

  The same is done for the "Folder content" functions and "favorite" folders. However, these submenus are only filled with objects after they are opened by the user; this is done by intercepting the WM_INITMENU message in the subclassed folder frame window procedure (see below). XFolder also subclasses these submenu windows (and only these) to be able to paint icons and to intercept mouse button 2 for opening a folder.

  (Please note that "subclassing" here has nothing to do with WPS classes, but is the Presentation Manager terminology for using a different message procedure for an existing window in order to be able to intercept certain PM messages for that window. This is done using the WinSubclassWindow API.)

  XFolder also modifies various other menus (such as the the "Sort" submenu) in this method, if the Global Settings allow this, and adds other menu items, if these have been enabled in the Global Settings.
  

• wpMenuItemSelected: This is called by the WPS whenever a context menu item is selected by the user.

  XFolder checks if one of its own (variable) menu items was selected; if so, it finds the corresponding object in the configuration folder and opens it. If this object is of the WPProgram class, &xwp; performs the usual tricks on it (see the context help for the &xwp; Configuration Folder for details). If the object is a template, no matter of what WPS class, it is not opened, but XFolder creates a new object from it in the current folder (via wpCreateFromTemplate).

  If the selected item is one from the "folder content" submenus, the corresponding object is simply opened.

  If any of the other menu items that XFolder adds to context menus are selected, XFolder itself will perform the respective action internally.

  If none of the XFolder menu items was selected, the parent class's (WPFolder's) wpMenuItemSelected method is called (in order not to prevent the standard menu items from functioning).
  

• wpMenuItemHelpSelected: This is called by the WPS whenever you press F1 over a context menu item. XFolder will display a proper help page, if necessary.
  
• wpFilterPopupMenu: With this method, XFolder removes those default menu entries from the context menus that you have specified in the Global Settings. (This method is called by the WPS even before wpModifyPopupMenu, so first items are removed, then new items are inserted.)
  
• wpclsQueryTitle: The string XFolder (or whatever you have specified in the Global Settings) is returned to give the XFolder class a unique name.
  
• wpOpen: This routine is called by the WPS every time a folder (and any other object also) is opened. XFolder needs to override this method to implement a whole number of features.

  First, the parent method is called to have the folder view opened: the WPS will create a window with a container control in it and shows this window.

  XFolder then intercepts the frame window handle, with which it can then modify the folder's window title and reset it to the folders complete path (if enabled in the Global Settings). Basically, it's a simple WinSetWindowText call, with just a few calculations to truncate the title if necessary.

  In this method, XFolder also subclasses the folder frame window in order to be able to handle WM_CHAR messages for folder hotkeys and lots of other things. For subclassing, this method seemed the best place to me, since all necessary WPS initializiation stuff has been done by calling the parent method, but the user cannot interact with the folder yet, because it will only be filled with objects ("populated" in WPS terminology) on a different thread afterwards.

  In the new window procedure, XFolder intercepts all WM_CHAR messages (which are only passed to the frame window procedure if they have not yet been processed by the container already, such as cursor keys) and evaluates them according to its internal hotkey list, which can be changed in the Global Settings.

  Subclassing is also needed to introduce folder status bars; the WM_QUERYFRAMECTLCOUNT, WM_FORMATFRAME, and WM_CALCFRAMERECT messages are intercepted to resize the folder frame and its container child window according to the space needed for the folder status bar.

  XFolder also intercepts a few container notification messages in order to provide the "Auto-scroll Tree views" feature and update the status bar text if object selections have been changed by the user.

  In addition, XFolder intercepts various menu messages, such as WM_INITMENU and WM_MENUSELECT, to be able to handle some menu functions which are not accessible through regular WPS methods.

  All messages which have no meaning to XFolder are passed on to the original window procedure.

  The wpOpen method is also needed for implementing the XFolder extended sort functions; XFolder updates the container settings according to the sort criteria which you have specified.
  

• wpAddSettingsPages: This method is called by the WPS every time an object's settings notebook is opened. XFolder overrides this method also to add its own settings pages, after having called the parent method, so that the original settings pages are still inserted.

XFldObject doesn't do much visibly either, except for suppressing &os2; default menu items and adding the "Copy filename" feature. It is however required by other XFolder parts internally in order to be notified of some internal WPS events, especially the &xshutdown; feature, which is described in detail on the next page.

The XFldDesktop class is implemented to allow changing the Desktop menu items and for &xshutdown;, which is described in detail on the next page.

While previous versions also replaced the WPSystem class so that the "System" object in the "System setup" folder contained more notebook pages to access XFolder's Global Settings, with V0.80 this behavior has changed. Instead, XFolder registers two new classes derived from WPSystem without replacing it. These two classes are XFldSystem and XFldWPS for the "&os2; Kernel" and "Workplace Shell" objects, respectively. The settings that you specify here are (mostly) stored in OS2.INI and evaluated every time XFolder needs them (e.g. when you open a context menu). In contrast, the "local" XFolder settings for an individual folder are stored in its .CLASSINFO Extended Attributes, where the WPS also stores the other folder settings. This is then done by the XFolder class.

Please note that all the XFolder classes are designed to interact. Do not try to remove only SOME of them, or XFolder might behave in a funny way (if you're lucky). All of XFolder's features have been made fairly configurable, so you should be able to get rid of what you don't like -- or to get rid of XFolder altogether.