CGDI - Simple GDI Set And Reset

// Example to draw a line using the BLACK_PEN stock object
void DrawLine(CDC* pDC)
{
    CStockObject theObject(pDC, BLACK_PEN);

    pDC->LineTo(100, 100);
}

// Example to draw a line using a custom pen
void DrawLinesWithPen(CDC* pDC)
{                                                         // Current Pen Selected
    CPen thePen(PS_SOLID, 3, RGB(100, 200, 2));

    CGDIObject<CPen> theObject(pDC, &thePen);                  // thePen Selected

    pDC->LineTo(100, 100);

    // Use brackets to nest calls
    {
        CPen theOtherPen(PS_SOLID, 3, RGB(200, 10, 2));         

        CGDIObject<CPen> theOtherObject(pDC, &theOtherPen);    // theOtherPen Selected

        pDC->LineTo(200, 200);
    }                                                     // thePen Selected

    pDC->LineTo(300, 300);
}                                                         // Current Pen Selected




// helper template function for unused parameters
template <class T>
void Unused(T rT)
{
    static_cast<void>(rT);
};


class CGDI
{
protected:
    CDC* m_pDC;

    CGDI(CDC* pDC) : 
      m_pDC(pDC)
    {
    }

    virtual ~CGDI()
    {
        m_pDC = NULL;
    }
};

// Class to select a stock object
class CGDIStockObject : public CGDI
{
    CGdiObject* m_pLastObject;

public:
    CGDIStockObject(CDC* pDC, int nIndex) : CGDI(pDC),
      m_pLastObject(NULL)
    {
        m_pLastObject = m_pDC->SelectStockObject(nIndex);
    }

    virtual ~CGDIStockObject()
    {
        if (m_pLastObject)
        {
            Unused(m_pDC->SelectObject(m_pLastObject));

            m_pLastObject = NULL;
        }
    }
};


class CGDITextColor : public CGDI
{
    COLORREF m_LastColor;

public:
    CGDITextColor(CDC* pDC, COLORREF theColor) : CGDI(pDC),
      m_LastColor(RGB(0,0,0))
    {
        m_LastColor = m_pDC->SetTextColor(theColor);
    }

    virtual ~CGDITextColor()
    {
        Unused(m_pDC->SetTextColor(m_LastColor));
    }

};

class CGDIBackColor : public CGDI
{
    COLORREF m_LastColor;

public:
    CGDIBackColor(CDC* pDC, COLORREF theColor) : CGDI(pDC),
      m_LastColor(RGB(0,0,0))
    {
        m_LastColor = m_pDC->SetBkColor(theColor);
    }

    virtual ~CGDIBackColor()
    {
        Unused(m_pDC->SetBkColor(m_LastColor));
    }

};

class CGDIBackMode : public CGDI
{
    int m_LastMode;

public:
    CGDIBackMode(CDC* pDC, int theMode) : CGDI(pDC),
	  m_LastMode(0)
    {
        m_LastMode = m_pDC->SetBkMode(theMode);
    }

    virtual ~CGDIBackMode()
    {
        Unused(m_pDC->SetBkMode(m_LastMode));
    }

};

// This class can be used like this:
// CGDIObject<CFont>(pDC, pFont);
// CGDIObject<CPen>(pDC, pPen);

template <class T>
class CGDIObject : public CGDI
{
T* m_pLast;

public:
    CGDIObject(CDC* pDC, T* pObject) : CGDI(pDC), 
	  m_pLast(NULL)
    {
        if (pObject)
        {
            m_pLast = pDC->SelectObject(pObject);
        }
    }

    virtual ~CGDIObject()
    {
        if (m_pLast)
        {
            Unused(m_pDC->SelectObject(m_pLast));

            m_pLast = NULL;
        }
    }
};

class CGDITextAlign : public CGDI
{
UINT m_Last;

public:
    CGDITextAlign(CDC* pDC, UINT nTextAlign) : CGDI(pDC),
	  m_Last(0)
    {
        m_Last = pDC->SetTextAlign(nTextAlign);
    }

    virtual ~CGDITextAlign()
    {
        Unused(m_pDC->SetTextAlign(m_Last));
    }
};


class CGDIROP : public CGDI
{
int m_Last;

public:
    CGDIROP(CDC* pDC, int nROP) : CGDI(pDC),
	  m_Last(0)
    {
        m_Last = pDC->SetROP2(nROP);
    }

    virtual ~CGDIROP()
    {
        Unused(m_pDC->SetROP2(m_Last));
    }
};

class CGDIMapMode : public CGDI
{
int m_Last;

public:
    CGDIMapMode(CDC* pDC, int nMapMode) : CGDI(pDC),
	  m_Last(0)
    {
        m_Last = pDC->SetMapMode(nMapMode);
    }

    virtual ~CGDIMapMode()
    {
        Unused(m_pDC->SetMapMode(m_Last));
    }
};