Subclassing and Hooking with Visual Basic

A System-Wide Example

Allowing a single application to make use of the Windows key is nice, but it would be better if we could add a system-wide Windows key function. Taking the previous example one step further, we could create the hook with a system-wide scope so that no matter which application you were in, you could always press the Windows key along with the “w” key, and Internet Explorer would start. This is similar in concept to Windows’ default behavior of launching Windows Explorer when the user presses the Windows key along with the “e” key.

The UI for this application, which Figure 12-4 illustrates, is very simple. The Hook button simply installs the hook by injecting the C++ DLL containing the filter function into all running processes. Now we can press the Hook button and have Internet Explorer start when we press the Windows key and the “w” key. The Unhook button removes the hook from all running processes.

Figure 12-4. Screenshot of system-wide keyboard hook application

Table 12-2 presents the nondefault properties of the form and its controls.

Table 12-2. Nondefault Properties of the Form and Its Controls

Object Type	Property Name	Property Value
Form	Name	SysForm1
Form	Caption	“SysKeyHk”
Form	BorderStyle	3-Fixed Dialog
Form	Top	420
Form	Left	132
Form	Height	1455
Form	Width	1695
Command Button1	Name	cmdHook
Command Button1	Caption	“Hook” ...