bezier_curve.md
In rswipl: Embed 'SWI'-'Prolog'

class bezier_curve {#class-bezier_curve}

Class bezier_curve implements Bezier curves. A bezier smooth curve is a curve from <-start to <-end using either one or two control-points. They are used to create a smooth connection from a certain point leaving at a defined direction to another point arriving in some direction.

XPCE's class bezier_curve is a subclass of class joint, inheriting the possibility to have arrow objects at either end of the curve.

To get a feeling for the behaviour of this class, please try PceDraw from the demo programs (File/Demo Programs).

When ->selected, the system will show the control-points connected by dotted lines.

A good description of the details on Bezier curves can be found at http://graphics.cs.ucdavis.edu/CAGDNotes/ See also class path.

bezier_curve<-control1: point The attributes <-control1 and <-control2 define the Bezier curve's control-points. If <-control2 = @nil, the curve has only a single control-point and is known as a quadratic Bezier curve. If the second control point is specified, it is known as a cubic Bezier curve.

The curve departs from <-start in the direction of <-control1 and ends in <-end from the direction of <-control2 (or <-control1 if <-control2 is @nil. Unlike class path, the curve does not go through its control-points.
bezier_curve<-control2: point Inherits description from*: bezier_curve-control1

bezier_curve->control1: point 1st Control-point of the Bezier curve.
bezier_curve->control2: point Inherits description from*: bezier_curve-control1, bezier_curve->control1
bezier_curve->geometry: x=[int], y=[int], width=[int], height=[int] The graphical->geometry method is redefined by class bezier to move the bezier curve.
bezier_curve->initialise: start=point, end=point, control1=point, control2=[point]* Create a bezier_curve object starting at start going to end using either one (quadratic) or two (cubic) control-points.
bezier_curve->selected: bool Refines graphical->selected to deal with the <-area change resulting from displaying the control-points.

The control-points and dotted connection-lines are visible if the window<-selection_feedback is set to handles.
bezier_curve->set_point: point=point, x=[int], y=[int] Move (member) point to (X, Y). Depending on the point, this modifies <-start, <-control1, <-control2 or <-end and ->compute's the curve afterwards,

It is normally used with the result if <-point to allow interactive editing of bezier curves. See also the PceDraw demo application.

bezier_curve<-point: near=point|event, max_distance=[int] -> point Find closest point. This method is intended for editing and returns the closest of <-start, <-control1, <-control2 or <-end that is within max_distance.

This method is designed after path<-point. See also ->set_point.