Trend Display

• Download source files - 9 Kb
• Download demo project - 65 Kb

What is Trend Display?

Trend Display is an area to show time dependent values in form of curves for different purposes. For example if you want to monitor some hardware quantities that are time dependent such as voltage, temperature and something like these the Trend Display is a good area to display the changes of those signals value in different times.

How does it work?

For this purpose I've created a CFormView based class called CTrendView with related document and frame classes ( CTrendDoc and CTrendFrame ). By using these classes in a MDI project you can have a multiple documents Trend Display. It's very easy to use. Just you should register the Trend's document templates in InitInstance() method of application class.

// declaration in header file 
CMultiDocTemplate* pDocTemplate;  
m_pTrendTemplate = new CMultiDocTemplate(IDR_TrendTestTYPE, 
        RUNTIME_CLASS(CTrendDoc), 
        // custom MDI child frame 
        RUNTIME_CLASS(CTrendFrame), 
        RUNTIME_CLASS(CTrendView)); 
AddDocTemplate(m_pTrendTemplate); 

Also because of using a CFormView class you need to add a dialog resource (IDD_FORMVIEW) to your project. Now you can open Trend Display in any way you desire for example through a menu or toolbar.

void CTrendTestApp::OnTrendOpen() 
{ 
    m_pTrendTemplate->OpenDocumentFile(NULL); 
}

A ruler that moves horizontally, signifies the current time. This ruler moves pixel by pixel by a timer, which is used in CTrendView class. There is no need to any special code for invalidating the OnDraw function when Trend window moves, resize or disappears behind the other windows, because there is a buffer to hold the values for each signal.

void CTrendView::DrawTrend() 
{ 
    m_pDC = GetDC(); 
    for(BYTE j=0 ; j < m_pDoc->m_noOfPoint ; j++) 
    { 
        CPen pen(PS_SOLID,1,m_pDoc->m_pPoint[j].Color); 
        m_OldPen = m_pDC->SelectObject(&pen); 
        for(int i=1 ; 
            i < m_pDoc->m_pPoint[j].BufferedValue.GetSize(); 
            i++) 
        { 
            m_portion = 
                (m_pDoc->m_pPoint[j].BufferedValue[i-1] -
                m_pDoc->m_pPoint[j].Min)
                / m_pDoc->m_pPoint[j].Range; 

            m_pDC->MoveTo(m_trendRect.left+i-1,
                int(m_trendRect.bottom - 
                m_portion*m_trendRect.Height())); 

            m_portion = (m_pDoc->m_pPoint[j].BufferedValue[i] - 
                m_pDoc->m_pPoint[j].Min)
                / m_pDoc->m_pPoint[j].Range; 

            m_pDC->LineTo(m_trendRect.left+i, 
                int(m_trendRect.bottom -
                m_portion*m_trendRect.Height())); 
        } 
        m_pDC->SelectObject(m_OldPen); 
    } 
    InvalidateRect(CRect(m_trendRect.left + 
        m_timeStep-1, m_trendRect.top, 
        m_trendRect.left+m_timeStep+1,m_trendRect.bottom)); 

    ReleaseDC(m_pDC); 
}

I didn't use any options for this project but it could has many options. For example the back ground color and signals color can be changeable and grids, scales and scan time as well. May be in my upcoming version I add these options to my code. But it's better that you put these possibilities as you desire. The attached demo project is created and compiled with MFC7, so to compile it, you need VS.NET but it's very easy to add source code to your MFC6 based project. Please feel free to send your comments, questions and suggestions about this Trend Display. Thank you in advance.