Subclassing and Hooking with Visual Basic

Microsoft Tools

Microsoft provides some useful debugging tools along with its development products. You can find these tools on Microsoft’s web site. They also are bundled with Visual C++ and VB.

Spy++

Spy++ is one of the most useful tools to give us insight on how our application is structured, as well as to allow us to examine the messages our application is receiving. I have provided an introduction to using this tool in Chapter 1. Throughout many of the chapters, I have described specific uses of this tool as it relates to each chapter’s topic.

DBGWPROC.DLL

This tool, which Microsoft designed, is available at http://msdn.microsoft.com/vbasic/downloads/controls.asp. This tool is provided free of charge.

This is simply a Component Object Model (COM) DLL that you add to your application. You need to add very little code to allow your application to use this DLL.

To incorporate this DLL into your application, register it using regsvr32.exe and add it to your project references by checking the “Debug Object for AddressOf Subclassing” option in the References dialog. Click on the Make tab in the Project Properties dialog box. Add the text

DEBUGWINDOWPROC = -1 : USEGETPROP = -1

to the Conditional Compilation text box. For the release version of this application, you should change the -1 values to zeroes and remove the reference to DBGWPROC.DLL.

Next, you must create an object m_DbgHook from the WindowProcHook class.

#If DEBUGWINDOWPROC Then Private m_DbgHook As WindowProcHook #End If ...