Initiate Stroke Drawing

The OnLButtonDown member function is called via the message map when Windows sends a WM_LBUTTONDOWN message to the view object. The function begins a new stroke, adding the current location of the mouse to the stroke and adding the stroke to the document’s stroke list. Then OnLButtonDown captures the mouse — until the left mouse button is released to end the stroke.

To add code for OnLButtonDown

1. Using WizardBar, jump to CScribbleView’s member function OnLButtonDown in ScribbleView.cpp.

2. Replace the //TODO comments and code with the code shown here:

   // Pressing the mouse button in the view window
   // starts a new stroke.
   
   m_pStrokeCur = GetDocument( )->NewStroke( );
   // Add first point to the new stroke
   m_pStrokeCur->m_pointArray.Add(point);
   
   SetCapture( );  // Capture the mouse until button up
   m_ptPrev = point;  // Serves as the MoveTo( ) anchor point
   // for the LineTo() the next point, as
   // the user drags the mouse
   return;
   

   Note   This version of OnLButtonDown doesn’t include a call to the base class version. It completely replaces the inherited behavior.