C / C++ / MFC

void CMainFrame::OnLButtonDown (UINT nFlags,
CPoint MousePt)
{
int ShortDist;

if (nFlags & MK_SHIFT)
{
// Shift key down. So delete closest point.
if (nPts > 0) // - only if have one
{
// Step: Find point closest to MousePt
Pos = ClosestPoint (MousePt,ShapePts,nPts, ShortDist); <-- returns int
Undo[nUndo] = ShapePts[nPts]; // nPts and nUndo were initialized to
// zero in MainFrame contructor

// Step: Shift points down one array component index
for (int i = Pos + 1; i < nPts; i++)
{
ShapePts[i-1] = ShapePts[i];
}

nPts--; // adjust count
} // end if
}
else
{
if (nPts >= 99) // array full
return; // do nothing
else
{
ShapePts[nPts] = MousePt;
nPts++;

CString s;
s.Format("Last pt d, %d)",MousePt.x, MousePt.y);
myStatusBar.SetText (s,1,SBT_NOBORDERS);
}
}
Invalidate();
}

void CMainFrame::OnRButtonDown (UINT nFlags, CPoint MousePt)
{
CPoint ScreenPt;
int ShortestDist, i;

// Step 1: Find position of closest pt in array
Pos = ClosestPoint (MousePt, ShapePts, nPts, ShortestDist);

if(nFlags & MK_SHIFT)
{
ShapePts[nPts] = Undo[nUndo];
nPts++;

for(i = 0; i < nUndo; i++)
{

Undo[i-1] = Undo[i];
}

nUndo--;
}
else
{


SetCapture();



// Step 2: Move the cursor to that position
ScreenPt = ShapePts[Pos];
ClientToScreen (&ScreenPt);
SetCursorPos (ScreenPt.x, ScreenPt.y);
}
}