Microsoft KB Archive/81334

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KBHook2.exe Demonstrates Using a WH_KEYBOARD Hook

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Q81334

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The information in this article applies to:


 * Microsoft Windows Software Development Kit (SDK) 3.1

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SUMMARY
KBHOOK2 is a file in the Software Library that contains sample code to demonstrate installing and using a system-wide WH_KEYBOARD keyboard filter function (otherwise known as a keyboard hook function). This code monitors the status of the CAPS LOCK key. Whenever the CAPS LOCK key is pressed, its status is displayed on the application's icon. Terminating the application removes the keyboard filter from the system.

KBHOOK2 updates the KBHOOK sample to use new functions provided by Windows 3.1.

MORE INFORMATION
The following files are available for download from the Microsoft Download Center:

KBHook2.exe

For additional information about how to download Microsoft Support files, click the article number below to view the article in the Microsoft Knowledge Base:

"Q119591 How to Obtain Microsoft Support Files from Online Services" Microsoft used the most current virus detection software available on the date of posting to scan this file for viruses. Once posted, the file is housed on secure servers that prevent any unauthorized changes to the file.

KBHOOK2 contains an application program, KEYAPP, and a dynamic-link library (DLL), KEYHOOK, that implements the keyboard filter function. The KEYHOOK DLL uses the new Windows 3.1 hook functions: SetWindowsHookEx, UnhookWindowsHookEx, and CallNextHookEx.

KEYAPP calls KEYHOOK to install the keyboard filter function and then makes itself iconic. Windows calls KEYHOOK each time a key is pressed. When the CAPS LOCK key is pressed, KEYHOOK posts a message to KEYAPP. KEYAPP processes the message by painting its icon to display the current state of CAPS LOCK. When KEYAPP is terminated, the KEYHOOK filter is removed from the system.

NOTE: Compiling this sample as is will fail with the error that the include file CONVDLL.INC cannot be found. To correct the problem, simply remove the line

"INCLUDE CONVDLL.INC" from the LIBENTRY.ASM.

Additional query words:

Keywords : kbfile kbsample kb16bitonly kbHook kbSDKPlatform kbGrpDSUser kbOSWin310

Issue type :

Technology : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310