Advanced MFC Programming

Chapter 13. Adding Special Features to Application
implementing the playback, parameter code indicates what we need to do: if it is HC_SKIP, we need to get
the next event for playback; if it is HC_GETNEXT, we need to copy the event to an EVENTMSG type object
whose address can be obtained from parameter lParam. Here is how we get the next event when parameter
code is HC_SKIP:
……
……
if(code == HC_SKIP)
{
if(lpEventPlay->lpNextEvent == NULL)
{
free(lpEventHead);
lpEventHead=lpEventPlay=NULL;
UnsetJournalPlaybackHook();
PostMessage(g_hWnd, uMsgFinishJournal, (WPARAM)TRUE, (LPARAM)NULL);
}
Here, if there is no more event, we need to reset everything and send a message (the message is a user
defined message WM_FINISHJOURNAL, see below) to the mainframe window of the application indicating that
the playback is over. If there are still events left, we get the next recorded event and free the buffers holding
the event that is being played back. If parameter code is HC_GETNEXT, we need to obtain an EVENTMSG type
pointer from parameter lParam, and copy the event pointed by lpEventPlay to the object pointed by this
pointer. When doing this copy, we need to add an offset to the time stamp because originally it indicates the
time when the events were recorded:
……
else
{
lpEventPlay=lpEventPlay->lpNextEvent;
free(lpEventHead);
lpEventHead=lpEventPlay;
}
}
else if(code == HC_GETNEXT)
{
lpEvent=(LPEVENTMSG)lParam;
lpEvent->message=lpEventPlay->Event.message;
lpEvent->paramL=lpEventPlay->Event.paramL;
lpEvent->paramH=lpEventPlay->Event.paramH;
lpEvent->time=lpEventPlay->Event.time+dwTimeAdjust;
lReturnValue=lpEvent->time-GetTickCount();
if(lReturnValue < 0L)
{
lReturnValue=0L;
lpEvent->time=GetTickCount();
}
return lReturnValue;
}
Using Functions Contained in DLL
To notify the mainframe window about journal finishing event, a user registered message is used to
communicate between the application and DLL. In the DLL, function ::RegisterMessage() is called after
it is loaded, which will register WM_FINISHJOURNAL message in DLL. This message is also registered in the
application’s CMainFrame::OnCreate(…) function. In the sample, two menu commands Macro | Record
and Macro | Playback are added to the application. To avoid journal playback, journal record and
keyboard hook from getting entangled, only one of the three hook related commands are enabled at any
time. Besides this, playback hook could not be installed if journal record hook has not been installed. This
is controlled by the following two variables declared in the application: CMainFrame::m_bEnableMenu,
CMainFrame::m_bPlayAvailable.
Installing and removing the hooks is simple. The following three functions show how the journal
record hook and journal playback hook are implemented in the application. Here,
CMainFrame::OnMacroRecord() implements command Macro | Record,
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