PRB: Using ToAscii() in Journal Record Hooks

• Microsoft Windows Software Development Kit (SDK) for Windows, version 3.1

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).