Drawing

On drawing the control the values of the variables are read via their dispatch drivers, and accordingly one of the four defined bitmaps is displayed. When the value of a variable changes, the control is updated by the OnDraw routine.

void CLatchedSwitchCtrl::OnDraw(CDC* pdc, const CRect& rcBounds, const CRect& rcInvalid)

{

CRect rcBitmap = rcBounds;

rcBitmap.NormalizeRect();

if (!m_dElement)

{

m_SwitchOn.Render(pdc, &rcBounds, &rcBounds);

return;

}

BOOL bVal1 = 0, bVal2 = 0;

VARIANT vRes;

if (m_dSwitchVar) // Variable exists?

{

vRes = m_dSwitchVar.GetValue();

bVal1 = (BOOL)VariantToDouble(&vRes);

}

if (m_dLatchVar) // Variable exists?

{

vRes = m_dLatchVar.GetValue();

bVal1 = (BOOL)VariantToDouble(&vRes);

}

if (bVal1 && bVal2)

m_SwitchOn.Render(pdc, rcBitmap, rcBitmap);

else if (!bVal1 && bVal2)

m_SwitchOff.Render(pdc, rcBitmap, rcBitmap);

else if (bVal1 && !bVal2)

m_LatchedOn.Render(pdc, rcBitmap, rcBitmap);

else

m_LatchedOff.Render(pdc, rcBitmap, rcBitmap);

}