# HOpConstructNurbsCurve

## Functions

| `HOpConstructNurbsCurve`
| `~HOpConstructNurbsCurve`
HBaseOperator * | `Clone`
const char * | `GetName`
int | `OnNoButtonDownAndMove`
int | `OnLButtonDown`
int | `OnLButtonDblClk`
int | `OnMButtonDown`

## Detailed Description

class HOpConstructNurbsCurve : public HOpConstructPolyline

  The HOpConstructNurbsCurve class provides support for constructing a Non Uniform Rational B-Spline (NURBS) curve and inserting it into the model.

  HOpConstructNurbsCurve implements one of the mouse event handlers defined on the base class and extends three of the mouse event handlers defined on HOpConstructPolyline. The class employs all of the drawing functionality of HOpConstructPolyline to draw a temporary, overlayed NURBS curve and associated ‘control polyline’ in the view plane, and then uses the HOOPS routine HC_Insert_NURBS_Curve to add a curve to the model.

  The operation consists of the following steps:

  1. Left Button Down: The operation is initiated and the first point of the curve is recorded.

  2. No Button Down and Drag: Rubberbands the line segment to a desired position for the next point.

  3. Left Button Down: The next point on curve is recorded and the cycle continues until a left button double click event occurs.

  4. Left Button Double Click: The curve is finalized, the temporary control polyline is flushed and the NURBS curve is inserted into the model.

  More Detailed Description: see event methods.

  Subclassed by HOpCreateNurbsCurve

  Public Functions

  HOpConstructNurbsCurve(HBaseView *view, int DoRepeat = 0, int DoCapture = 1)

    Constructs an HOpConstructNurbsCurve object.

    Parameters

      - view – A pointer to an HBaseView object.

      - DoRepeat – An integer denoting whether this is a repeatable operator. This parameter has been deprecated.

      - DoCapture – An integer denoting whether the mouse state should be captured, which means that all mouse events should be received after a mousedown, even if it leaves the window. This parameter has been deprecated.

  virtual ~HOpConstructNurbsCurve()
  virtual HBaseOperator *Clone()

    Creates a new operator which is a copy of the current operator. The user is responsible for deleting the newly created operator.

    Returns

      A pointer to the newly created HOpConstructNurbsCurve object.

  virtual const char *GetName()
    Returns

      A pointer to a character string denoting the name of the operator, which is ‘HOpConstructNurbsCurve’.

  virtual int OnNoButtonDownAndMove(HEventInfo &hevent)

    OnNoButtonDownAndMove draws a rubberbanded polyline from the previous point in the array to the current mouse position. If the number of points in the array has exceeded the degree of the NURBS curve where the default is 2, the polyline construction segments will already have been replaced with a NURBS curve. In this case, OnNoButtonDownAndMove replaces the entire construction NURBS curve with an updated version that accounts for the current pointer position.

    Parameters

      hevent – An HEventInfo object containing information about the current event.

    Returns

      An HOperatorReturn indicating the status of the event.

  virtual int OnLButtonDown(HEventInfo &hevent)

    OnLButtonDown records the first mouse position and initiates the polyline-drawing mechanism used in HOpConstructPolyline. When the number of points in the polyline array exceeds the degree of the NURBS curve where the default is 2, OnLButtonDown replaces the construction polyline with a construction NURBS curve.

    Parameters

      hevent – An HEventInfo object containing information about the current event.

    Returns

      An HOperatorReturn indicating the status of the event.

  virtual int OnLButtonDblClk(HEventInfo &hevent)

    OnLButtonDblClk directs the final mouse position into the temp array, then inserts the array into the database as a NURBS curve. This function also takes care of any cleanup.

    Parameters

      hevent – An HEventInfo object containing information about the current event.

    Returns

      An HOperatorReturn indicating the status of the event.

  virtual int OnMButtonDown(HEventInfo &hevent)

    OnMButtonDown passes a middle-button down event to OnLButtonDown.

    Parameters

      hevent – An HEventInfo object containing information about the current event.

    Returns

      An HOperatorReturn indicating the status of the event.