Implementing Hit Testing

POINT pt;   
VECTOROBJECT Object;   
L_TCHAR szBuffer[ 80 ];   
VECTORPEN Pen; 

case WM_MOUSEMOVE: 
// hit test object under mouse cursor 
pt.x = LOWORD( lParam ); 
pt.y = HIWORD( lParam ); 
nRet = L_VecHitTest( &Vector, &pt, &Object ); 
if( nRet == SUCCESS ) 
{ 
   // theres an object, show its type in main window caption 
   switch( Object.nType ) 
   { 
      case VECTOR_VERTEX: lstrcpy( szBuffer, TEXT("Vertex ")); break; 
      case VECTOR_LINE: lstrcpy( szBuffer, TEXT("Line ")); break; 
      case VECTOR_RECTANGLE: lstrcpy( szBuffer, TEXT("Rectangle ")); break; 
      case VECTOR_POLYLINE: lstrcpy( szBuffer, TEXT("Polyline")); break; 
      case VECTOR_POLYBEZIER: lstrcpy( szBuffer, TEXT("Polybezier")); break; 
      case VECTOR_POLYGON: lstrcpy( szBuffer, TEXT("Polygon")); break; 
      case VECTOR_ELLIPSE: lstrcpy( szBuffer, TEXT("Ellipse")); break; 
      case VECTOR_CIRCLE: lstrcpy( szBuffer, TEXT("Circle")); break; 
      case VECTOR_ARC: lstrcpy( szBuffer, TEXT("Arc")); break; 
      case VECTOR_TEXT: lstrcpy( szBuffer, TEXT("Text")); break; 
      case VECTOR_PIE: lstrcpy( szBuffer, TEXT("Pie")); break; 
      case VECTOR_CHORD: lstrcpy( szBuffer, TEXT("Chord")); break; 
      case VECTOR_RASTER: lstrcpy( szBuffer, TEXT("Raster ")); break; 
   } 
} 
else 
   lstrcpy( szBuffer, TEXT("No object under mouse cursor")); 
SetWindowText( hWnd, szBuffer ); 
break; 
case WM_LBUTTONDOWN: 
// hit test object under mouse cursor 
pt.x = LOWORD( lParam ); 
pt.y = HIWORD( lParam ); 
nRet = L_VecHitTest ( &Vector, &pt, &Object ); 
if( nRet == SUCCESS ) 
{ 
   // theres an object, flip its pen width between 1 and 4 
   L_VecGetObjectAttributes ( &Vector, &Object, NULL, &Pen, NULL, NULL ); 
   Pen.NewPen.LogPen.lopnWidth.x = ( Pen.NewPen.LogPen.lopnWidth.x == 1 ) ? 4 : 1; 
   L_VecSetObjectAttributes ( &Vector, &Object, NULL, &Pen, NULL, NULL, 0L ); 
   // reflect our changes 
   InvalidateRect( hWnd, NULL, FALSE ); 
} 
break; 
case WM_RBUTTONDOWN: 
// hit test object under mouse cursor 
pt.x = LOWORD( lParam ); 
pt.y = HIWORD( lParam ); 
nRet = L_VecHitTest ( &Vector, &pt, &Object ); 
if( nRet == SUCCESS ) 
{ 
   // theres an object, delete it 
   L_VecDeleteObject ( &Vector, &Object, 0L ); 
   // reflect our changes 
   InvalidateRect( hWnd, NULL, FALSE ); 
} 
break;