MtBackgroundThread.cpp

All the code for the background thread is contained in MtBackgroundThread.cpp.

unsigned long _stdcall CMtBackgroundApp_WorkerThread(void* pvData) {

    // Data items
    typedef struct tagDataItem {
        const char* name;
        double baseValue, value;
    } DataItem;

    static DataItem items[] = {
        { "one", 1.0 },
        { "two", 2.0 },
        { "three", 3.0 },
        { "four", 4.0 },
        { 0 }
    };

    CMtBackgroundApp* addin = (CMtBackgroundApp*)pvData;
    int whichItem = -1;

    // Get a list of all local hard drives
    std::vector<CString> vecDrives;
    GetDrives(vecDrives);

    // Loop until killed
    while (TRUE) {
        ::Sleep(addin->GetTickPeriod()); 

        // Update disk space for each local hard drive
        for (int i = 0; i < vecDrives.size(); i++)
            addin->PostMessage(new CMtBackgroundMsg(vecDrives[i], GetDiskSpace(vecDrives[i])));

        // Update memory usage
        addin->PostMessage(new CMtBackgroundMsg("mem", GetMemUse()));

        // Select the next item
        if (items[++whichItem].name == 0)
            whichItem = 0;

        // Change item value
        DataItem* item = items + whichItem;
        item->value = item->baseValue + ((double)rand() / (double)RAND_MAX);

        // Tell the main thread about the changed item
        addin->PostMessage(new CMtBackgroundMsg(item->name, item->value));
        
    }
    // Never reached
    return 0;
}

The most important line in the initialisation section is:

CMtBackgroundApp* addin = (CMtBackgroundApp*)pvData;

The thread keeps a pointer to the application class, which it will use to post messages to it.

In the main loop, the thread sleeps for TickPeriod milliseconds, and then wakes up and generates the three types of data.

1. It measures the disk space available on each hard drive.
2. It gets the total amount of memory in use.
3. Finally, it generates a single random number for a single topic, selecting the topic among "one", "two", "three" and "four" on a round-robin basis.

In each case the thread posts the data to the main thread wrapped up in a CMtBackgroundMsg object, e.g.:

addin->PostMessage(new CMtBackgroundMsg("mem", GetMemUse()));

Note that the message is created in the background thread, but will be consumed and destroyed in the main thread.

The background thread loops until the main thread kills it with CloseHandle(m_thread).

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