Multitouch Piano Dialog Based application - visual-c++

Question

I have made a dialog based Piano application in which i am handling Multitouch messages . I have two classes One is CMIDIKeyboard in which i am handling touch down messages as follows
LRESULT CMIDIKeyboard::OnTouchMessage( WPARAM wParam, LPARAM lParam ){
//Insert handler code here to do something with the message or uncomment the following line to test
//-------------------saurabh code------------------------------------------------------------------
UINT cInputs = (int) wParam; // Number of actual per-contact messages
TOUCHINPUT* pInputs = new TOUCHINPUT[cInputs]; // Allocate the storage for the parameters of the per-contact messages
if (pInputs == NULL)
{
return 0;
}
// Unpack message parameters into the array of TOUCHINPUT structures, each
// representing a message for one single contact.
if (GetTouchInputInfo((HTOUCHINPUT)lParam, cInputs, pInputs, sizeof(TOUCHINPUT)))
{
// For each contact, dispatch the message to the appropriate message
// handler.
for (unsigned int i = 0; i < cInputs; i++)
{
if (pInputs[i].dwFlags & TOUCHEVENTF_DOWN)
{
CPoint point;
CRect rect;
GetClientRect(&rect);
point=CPoint(pInputs[i].x-rect.left,pInputs[i].y-rect.top);
m_CurrKey= CPianoCtrl::FindKey(point);
m_Keys[m_CurrKey]->NoteOn(m_NoteOnColor,rect);
NotifyNoteOn(m_LowNote+m_CurrKey);
findchords(m_LowNote+m_CurrKey);
InvalidateRect(&rect);
CWnd::OnTouchMessage(wParam,lParam);
}
else if (pInputs[i].dwFlags & TOUCHEVENTF_UP)
{
//MessageBox("touchup!", "touchup!", MB_OK);
// g_pIManipProc->ProcessUp(pInputs[i].dwID, (FLOAT)pInputs[i].x, (FLOAT)pInputs[i].y);
}
else if (pInputs[i].dwFlags & TOUCHEVENTF_MOVE)
{
//MessageBox("touchmove!", "touchmove!", MB_OK);
//g_pIManipProc->ProcessMove(pInputs[i].dwID, (FLOAT)pInputs[i].x, (FLOAT)pInputs[i].y);
}
}
}
else
{
// error handling, presumably out of memory
ASSERT(FALSE && L"Error: failed to execute GetTouchInputInfo");
delete [] pInputs;
return 0;
//break;
}
if (!CloseTouchInputHandle((HTOUCHINPUT)lParam))
{
// error handling, presumably out of memory
ASSERT(FALSE && L"Error: failed to execute CloseTouchInputHandle");
delete [] pInputs;
return 0;
//break;
}
delete [] pInputs;
//--------------------------------------------------------saurabh code ends-----------------
//MessageBox("touch!", "touch!", MB_OK);
return 0;}
But on playing the piano keys first touch is playing proper ,but more than 1 touch is playing on piano keys enabling the last key on the right side irrespective of the touch position.
// ----------------------
// | | || | | | || || | |
// | |_||_| | |_||_||_| |
// | | | | | | | |
// ----------------------
// ^ ^
| |
one point More than
touch one touch
Can anybody please guide me or correct me please.

Answer 1

The TOUCHINFO documentation says:
x    The x-coordinate (horizontal point) of the touch input. This member is indicated in hundredths of a pixel of physical screen coordinates.
You cannot subtract a value measured in whole pixels (rect.left) from this value and expect the result to make sense.