Subclassing and Hooking with Visual Basic

Background Processing Example

The WH_FOREGROUNDIDLE hook example for this chapter will simply increment a number in a text box. Figure 14-3 shows a screenshot of the example application. This application has two buttons. The hook button will install the hook, and the unhook button will remove the hook. If the user tries to close the application before removing the hook, the application will display a message box informing the user to first click the unhook button and then shut down the application.

Figure 14-3. A screenshot of the example application

Table 14-1 lists the nondefault properties of the form and its controls.

Table 14-1. Nondefault Properties of the Form and Its Controls

Object Type	Property Name	Property Value
Form	Name	Form1
Form	Caption	“WH_FOREGROUNDIDLE Hook”
Form	Top	420
Form	Left	132
Form	Height	1572
Form	Width	6972
Text Box	Name	Text1
Text Box	Top	240
Text Box	Left	1440
Text Box	Height	1212
Text Box	Width	5412
Text Box	ScrollBars	3-Both
Frame	Caption	“IDLE”
Frame	Name	Frame1
Frame	Top	120
Frame	Left	120
Frame	Height	1335
Frame	Width	1155
Command Button	Name	Command1
Command Button	Caption	“hook”
Command Button	Top	300
Command Button	Left	120
Command Button	Height	315
Command Button	Width	915
Command Button	Name	Command2
Command Button	Caption	“unhook”
Command Button	Top