The OpenD Programming Language

Context.arc

Adds a circular arc of the given radius to the current path. The arc is centered at center, begins at angle1 and proceeds in the direction of increasing angles to end at angle2. If angle2 is less than angle1 it will be progressively increased by 2*PI until it is greater than angle1.

If there is a current point, an initial line segment will be added to the path to connect the current point to the beginning of the arc. If this initial line is undesired, it can be avoided by calling newSubPath() before calling arc().

Angles are measured in radians. An angle of 0.0 is in the direction of the positive X axis (in user space). An angle of PI/2.0 radians (90 degrees) is in the direction of the positive Y axis (in user space). Angles increase in the direction from the positive X axis toward the positive Y axis. So with the default transformation matrix, angles increase in a clockwise direction.

(To convert from degrees to radians, use degrees * (PI / 180))

This function gives the arc in the direction of increasing angles; see arcNegative() to get the arc in the direction of decreasing angles.

The arc is circular in user space. To achieve an elliptical arc, you can scale the current transformation matrix by different amounts in the X and Y directions. For example, to draw an ellipse in the box given by x, y, width, height:

cr.save();
cr.translate(x + width / 2, y + height / 2);
cr.scale(width / 2, height / 2);
cr.arc(Point(0, 0), 1, 0, 2 * PI);
cr.restore();
  1. void arc(Point!double center, double radius, double angle1, double angle2)
  2. void arc(double centerX, double centerY, double radius, double angle1, double angle2)
    struct Context
    void
    arc
    (
    double centerX
    ,
    double centerY
    ,
    double radius
    ,
    double angle1
    ,
    double angle2
    )

Parameters

radius double

the radius of the arc

angle1 double

the start angle, in radians

angle2 double

the end angle, in radians

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