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Q99337: PRB: Using ToAscii() in Journal Record Hooks

Article: Q99337
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): kbHook kbInput kbKeyIn kbOSWin2000 kbSDKWin32 kbGrpDSUser kbOSWin310
Last Modified: 09-JUL-2000

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
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SYMPTOMS
========

When a journal record hook procedure calls the ToAscii() function, dead keys are
apparently no longer processed correctly due to a side effect.

CAUSE
=====

The current implementation of ToAscii() determines whether the key that is
currently being processed is a dead key; if yes, it collapses the next keystroke
seen in the input stream with the dead key for Windows to display. This
assumption is being made for Windows, which calls the ToAscii() function during
normal processing of keystrokes. Calling ToAscii() in a journal record hook
clears the flag that indicates the presence of a dead key; thus, the key
combination will not be displayed correctly on the screen although it will
appear correctly when the recorded key strokes are played back.

RESOLUTION
==========

The journal record hook procedure should call the ToAscii() function twice with
the same parameters when processing a dead key [that is, the call to ToAscii()
returns -1]. This will reset the dead key flag internally.

Note that the source code for the ToAscii() function is publicly available
because it resides in the keyboard device driver whose source is shipped with
the Windows Device Development Kit (DDK).

Additional query words:

======================================================================
Keywords          : kbHook kbInput kbKeyIn kbOSWin2000 kbSDKWin32 kbGrpDSUser kbOSWin310 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbprb

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