Summary: Demonstrates how to dynamically draw text strings using the Rhino SDK.

On occasion, it is useful to dynamically display some text while in the middle of a point picking operation. Rhino's VariableFilletSrf command is a good example of a command that does this.

In order to add this capability to an SDK command, you will need to:

1. Derive a new class from CRhinoGetPoint.
2. Override the CRhinoGetPoint::DynamicDraw virtual function.
3. From within the DynamicDraw override, call CRhinoViewport::DrawString.

The following example code demonstrates how to derive a new class from CRhinoGetPoint, override the CRhinoGetPoint::DynamicDraw member, and draw text dynamically.

class CDrawStringGetPoint : public CRhinoGetPoint
{
public:
  CDrawStringGetPoint() {}
  void DynamicDraw( HDC hdc, CRhinoViewport& vp, const ON_3dPoint& pt );
};
 
void CDrawStringGetPoint::DynamicDraw( HDC hdc, CRhinoViewport& vp, const ON_3dPoint& pt )
{
  // Format active point as a string
  ON_wString str;
  RhinoFormatPoint( pt, str );
 
  // Build world-to-screen coordinate transformation
  ON_Xform w2s;
  vp.VP().GetXform( ON::world_cs, ON::screen_cs, w2s );
 
  // Transform point from world to screen coordinates
  ON_3dPoint screenpoint = w2s * pt;
 
  // Offset point so text does not overlap cursor
  screenpoint.x += 5.0;
  screenpoint.y += -5.0;
 
  // Draw string using the system font
  vp.DrawString( str, str.Length(), screenpoint, false, 0, 12, L"System" );
 
  // Allow base class to draw
  CRhinoGetPoint::DynamicDraw( hdc, vp, pt );
}

public class CDrawStringGetPoint : MRhinoGetPoint
{
  public override void  DynamicDraw(System.IntPtr hdc, MRhinoViewport viewport, IOn3dPoint pt)
  {
    MRhinoDisplayPipeline dp = viewport.DisplayPipeline();
    if( dp == null )
      return;
 
    // get screen point
    On2dPoint screen_pt = dp.Engine().WorldToScreenPoint(pt);
 
    int x = OnUtil.ON_Round(screen_pt.x);
    int y = OnUtil.ON_Round(screen_pt.y);
    // offset point so text does not overlap cursor
    screen_pt.x += 5.0;
    screen_pt.y -= 5.0;
    string msg = string.Format("screen {0}, {1}", x, y);
    dp.DrawString(msg, viewport.DrawColor(), screen_pt);
    // Allow base class to draw
    base.DynamicDraw(hdc, viewport, pt);
  }
}

Inherits MRhinoGetPoint
 
Public Overrides Sub DynamicDraw(ByVal hdc As System.IntPtr, _
                                 ByVal viewport As RMA.Rhino.MRhinoViewport, _
                                 ByVal pt As RMA.OpenNURBS.IOn3dPoint)
  Dim dp As MRhinoDisplayPipeline = viewport.DisplayPipeline()
  If (dp Is Nothing) Then Exit Sub
 
  ' get screen point
  Dim screen_pt As On2dPoint = dp.Engine().WorldToScreenPoint(pt)
 
  Dim x As Integer = OnUtil.ON_Round(screen_pt.x)
  Dim y As Integer = OnUtil.ON_Round(screen_pt.y)
  ' offset point so text does not overlap cursor
  screen_pt.x += 5.0
  screen_pt.y -= 5.0
  Dim msg As String = String.Format("screen {0}, {1}", x, y)
  dp.DrawString(msg, viewport.DrawColor(), screen_pt)
  ' Allow base class to draw
  MyBase.DynamicDraw(hdc, viewport, pt)
End Sub

End Class

You can use the above class as you would a CRhinoGetPoint object. Just create a new CDrawStringGetPoint object, initialize the class by calling base class members, and call it's GetPoint member. For example:

CRhinoCommand::result CCommandTest::RunCommand( const CRhinoCommandContext& context )
{
  CDrawStringGetPoint gp;
  gp.SetCommandPrompt( L"Pick test point" );
  gp.GetPoint();
  if( gp.CommandResult() != success )
    return gp.CommandResult();
 
  // TODO...
 
  return success;
}

public override IRhinoCommand.result RunCommand(IRhinoCommandContext context)
{
  CDrawStringGetPoint gp = new CDrawStringGetPoint();
  gp.SetCommandPrompt( "Pick test point" );
  gp.GetPoint();
  if( gp.CommandResult() != IRhinoCommand.result.success )
    return gp.CommandResult();
 
  return IRhinoCommand.result.success;
}

Public Overrides Function RunCommand(ByVal context As RMA.Rhino.IRhinoCommandContext) _
  As RMA.Rhino.IRhinoCommand.result
  Dim gp As New CDrawStringGetPoint()
  gp.SetCommandPrompt("Pick test point")
  gp.GetPoint()
  If (gp.CommandResult() <> IRhinoCommand.result.success) Then
    Return gp.CommandResult()
  End If
 
  Return IRhinoCommand.result.success
End Function