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 Care And Feeding Instructions

For The DbgWProc Debug DLL

The DbgWProc dll is the best thing since sliced bread when it comes to subclassing.  When used, it allows breaking in debug mode in the VB IDE without the crashes that are normally associated with break mode and subclassed code.  The following is a description of the proper installation and use of this tool.

You can install the DbgWProc dll anywhere on your system.  Because the dll is a COM library, it must be registered before it can be used.  To register the lib, you must use regsvr32.exe.  The most straightforward way to accomplish this registration is to place the DbgWProc lib in the System or System32 folder (depending on your OS) and then, in Windows Explorer, drag the DbgWProc.dll file and drop it on the regsvr32.exe file.  Regsvr32.exe will handle the rest.

Once the library is registered, you will be able to set a reference to it in the references dialog in the VB IDE.  The entry in the Available References list is: "Debug Object for AddressOf Subclassing"  After the reference is set, you should be able to declare a variable of type WindowProcHook.  For further details on how to setup a subclass, see Subclass Demo (Advanced).

Now that you have implemented the subclassing code, there are a couple of points to remember when running subclassed code in the VB IDE. 

• First and foremost, NEVER use the Stop button.  Using the Stop button does not allow the un-subclassing code to execute which leads to a certain crash of the IDE.  You should also remove any End statements from your code since End has the same effect as using the Stop button.

• If you have more than one subclass for a given object, make sure you unsubclass each subclass in the reverse order in which you subclassed the object.  This is to avoid orphaning the original window proc for the object, which would cause a crash.

• When you compile your application, don't forget to set the conditional compilation variable in the Make tab of the Project Properties dialog to '0' (zero) (see Subclass Demo (Advanced)).  If you don't, a message will be displayed stating the DbgWProc lib is not needed for running compiled code when your subclass code is accessed in the compiled app.

With proper use of the DbgWProc lib, subclassing in VB becomes a very stable and useful operation.  Happy Subclassing!