The behavior of mouse button 2 within the Source window depends on the Mouse button 2 behavior group box in the Debugger properties dialog (accessed from the Source or Session Control windows through Options->Debugger settings->Debugger properties).
Select one of the following check boxes to determine how mouse button 2 will behave in the Source window.
C++ example:.If Popup menus and step in white space is checked, and you click mouse button 2 on the C++ source line int myVar=18;, a popup menu appears if the pointer is over int, myVar, or 18, and a step command is performed if the pointer is on white space or the = or ; symbols.