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Example of C++ Code

// ******************************************************
// ***			   CURSOR		      ***
// ******************************************************

void TGCL_System::MoveCursor( const Rcoord& rNewCursorPos, uint flags )
{
    // given a new real coordinate, updates GDI and TGS cursors

    Rcoord rOldCursorPos;
    char num_string[CUR_FIELDWIDTH+1];
    char string[128];
    HDC hDC;				// temp DC
    POINT pt;				// temp point
    Rcoord rxy;
    Acoord axy;
    LUcoord luxy;
    LUcoord luWndTL;			// window boundary - lu
    LUcoord luWndBR;
    XYcoord dluxy;			// lu as double for range
    XYcoord dluCursorPos;		// lu as double for range
    double rc_prop;
    LUcoord luViewPos;			// current view pos
    bool on_dragpoint;
    MSG msg;


    rOldCursorPos = rCursorPos; 	// to test for a change
    rCursorPos = rNewCursorPos; 	// save new position


    // perform snap operation

    if( CursorSnap_rx != 0. )
	rCursorPos.x = round( rCursorPos.x / CursorSnap_rx, 0 ) *
	    CursorSnap_rx;

    if( CursorSnap_ry != 0. )
	rCursorPos.y = round( rCursorPos.y / CursorSnap_ry, 0 ) *
	    CursorSnap_ry;

    if( flags & CUR_AUTOSCROLL )
    {
	// get window dimensions as logical units
	// we must do this each time as the window may have scrolled

	// get device context for paint window
	hDC = GetDC( hWndPaint );
	if( !hDC )			// unable to get device context
	    _Sys_Error( SE_WINRESOURCE, 0xF329 );

	// set current window origin
	SetWindowOrg( hDC, luWindowOrg.x, luWindowOrg.y );

	GetClientRect( hWndPaint, &rect );

	if( !DPtoLP( hDC, (LPPOINT) &rect, 2 ) )    // -> logical units
	    _Int_Error( 0xF330 );	// conversion failed

	if( !ReleaseDC( hWndPaint, hDC ) )
	    _Sys_Error( SE_WINRESOURCE, 0xF331 );
					// unable to release device context

	luWndTL.x = rect.left;
	luWndTL.y = rect.top;
	luWndBR.x = rect.right;
	luWndBR.y = rect.bottom;


	if( flags & CUR_MOUSESCROLL )
	{
	    // has the mouse moved the GDI cursor outside or to the edge of
	    // the window ?

	    luxy = RealToLu( rNewCursorPos );

	    outside_left   = ( luxy.x <= luWndTL.x );
	    outside_right  = ( luxy.x >= luWndBR.x );
	    outside_top    = ( luxy.y <= luWndTL.y );
	    outside_bottom = ( luxy.y >= luWndBR.y );


	    // determine if real grid has zero net rotation

	    angle_r = RotationAngle_r - ViewRotation_r;
	    while( angle_r > +PI )		// limit range to +/-PI
		angle_r -= 2.*PI;		// for zero testing
	    while( angle_r < -PI )
		angle_r += 2.*PI;

	    zero_rotation = ( fabs( angle_r ) < ALMOST_ZERO );

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