The dialog editor is written as a library, to be invoked by other programs. As you can see, dialoged.cc is a very small program which invokes the main window via a wxResourceManager object. The wxResourceManager object controls the user interface and other aspects of the dialog editor.
There is wxResourceTable object in wxResourceManager: this contains a list of all the wxItemResources currently being edited. wxResourceTable and wxItemResource are classes already in wxWindows, defined in wx_res.h. In order to edit a new dialog box, the dialog is created, and the existing event handler is temporarily replaced with a new one which defines editing functionality. This allows existing dialogs - even instances of subclasses of wxDialogBox - to be edited, the application-specific functionality being temporarily taken over by the dialog editor.
In order to edit the properties of a dialog box or item, a property list editor is invoked. This uses the property classes from utils/wxprop. In order to map between properties and the actual window API, such as SetSize and GetSize, a 'proxy' class called wxPropertyInfo has been defined, with a subclass for each class of wxWindows window to be edited. This class defines the main members SetProperty, GetProperty, GetPropertyNames, which transform the normal API into 'property' terms.
Properties are mostly extracted directly from the window being edited. This is in contrast with wxBuilder, where everything is stored in a set of parallel data structures, and windows 'properties' only only set. However, there are exceptions to this rule in the dialog editor. There is in fact a set of parallel objects, the wxItemResource objects which can be seen listed in the main Dialog Editor window as a dialog is built up. These usually parallel the properties in the windows, but occasionally this is not possible. For example, all dialog boxes being edited must be modeless: or the user would not be able to access other windows. However, the user must be able to specify that when used in an application, that dialog box will be modal. In this case, the value in the wxItemResource will not match that in the actual dialog box.
There is a major problem with taking values directly from the windows: this information sometimes does not match what went in. In Motif and XView, size values returned are not the same as those given. This causes speedy 'degeneration' of window properties. Under Windows, properties are almost always consistent. The other platforms will need to be catered for by relying more on the wxItemResource objects, and not taking size information directly from windows.