Advanced MFC Programming

Chapter 13. Adding Special Features to Application
CMainFrame::OnMacroPlayback() implements command Macro | Playback, and
CMainFrame::OnFinishJournal(…) handles message WM_FINISHJOURNAL:
void CMainFrame::OnMacroPalyback()
{
m_bEnableMenu=FALSE;
SetJournalPlaybackHook(GetSafeHwnd(), hInstance);
}
void CMainFrame::OnMacroRecord()
{
m_bEnableMenu=FALSE;
SetJournalRecordHook(GetSafeHwnd(), hInstance);
}
LONG CMainFrame::OnFinishJournal(WPARAM wParam, LPARAM lParam)
{
if((BOOL)wParam == FALSE)
{
AfxMessageBox("Recording Finished");
m_bPlayAvailable=TRUE;
}
else
{
m_bPlayAvailable=FALSE;
AfxMessageBox("Playback Finished");
}
m_bEnableMenu=TRUE;
}
return TRUE;
To test the program, we can first execute Macro | Record command, then use mouse or keyboard to
generate a series of events. Next, we can press CTRL+F3 to stop recording. Finally we can execute Macro
| Playback command to see what has been recorded.
13.12Memory Sharing Among Processes
In sample applications created in section 13.8, we demonstrated how to share user defined messages
among different processes. However, with this method, we can send only simple parameter (integer) with
every message. Sometimes it is necessary to share complex data among different processes, in which case
we must apply memory sharing method.
Problem with Global Memory
Is it possible to share buffers allocated by ::GlobalAlloc(…) function among different processes? If
so, we can embed memory handle in the message parameters and send it to another process. Upon receiving
the message, the corresponding process can obtain the global memory handle and call ::GlobalLock(…) to
access all the memory buffers.
Unfortunately, although it is a possible method to share data among different processes for Win16
applications, it is not possible for us to do so for Win32 based applications. In a 32-bit operating system,
virtual memory is used to map physical memory to logical memory for each separate process, so each
process has its own memory space from 0 to infinity (ideally). Therefore, if the two processes have the
same logical address, they actually indicate different physical addresses. So if we send memory address
from one process to another, it will not indicate the original buffer.
File Mapping
To solve this problem, in Win32 platform, there is a new technique that allows different processes to
share a same block of memory. This technique is called file mapping, and can be used to let different
processes share either a file or a block of memory.
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