ccontext:Arc(xc, yc, radius, angle1, angle2)
radius to the current path. The
arc is centered at (xc, yc), 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 ccontext:NewSubPath() before calling ccontext: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 ccontext: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:
ctx:Save() ctx:Translate(x + width / 2, y + height / 2) ctx:Scale(width / 2, height / 2) ctx:Arc(0, 0, 1, 0, 2 * #PI) ctx:Restore() |