The journal record hook allows an application to monitor the system-message queue and to record input events. Typically, an application uses this hook to record a sequence of mouse and keyboard events that it can play back later by using the journal playback hook. A journal record hook function can be associated only with the system-message queue. The following code shows the syntax for a journal record hook function:

VOID EXPENTRY JournalRecordHook(HAB hab, PQMSG pQmsg)

The pQmsg parameter is a pointer to a QMSG data structure containing information about the message. The system calls the journal record hook function after processing the raw input enough to create valid WM_CHAR or mouse messages and after setting the window-handle field of the QMSG data structure.

A journal record hook function does not return a value, and the system always calls the next function in the chain. Typically, a journal record hook function saves the input events to a disk file to be played back later. The hwnd field of the QMSG data structure is not important and is ignored when the message is played back.

The following messages are passed to the journal record hook:

        WM_CHAR
        WM_BUTTON1DOWN
        WM_BUTTON1UP
        WM_BUTTON2DOWN
        WM_BUTTON2UP
        WM_BUTTON3DOWN
        WM_BUTTON3UP
        WM_MOUSEMOVE.

The positions stored in the mouse messages are in screen coordinates. The system does not combine mouse clicks into double clicks before calling the hook, because there is no guarantee that both clicks will be in the same window when they are played back.

The system passes a WM_JOURNALNOTIFY message to the journal record hook function whenever an application calls WinGetPhysKeyState or WinQueryQueueStatus. This message is necessary because the system-message queue is only one message deep while a playback hook is active. For example, the user might press the A, B, and C keys while in record mode. While the application is processing the A character message, the B key might be down; WinGetPhysKeyState returns this information. However, during playback mode, the system knows only that it currently is processing the A key.