arc in dc-path%

Extends or starts the path's open sub-path with a curve that corresponds to a section of an ellipse. The ellipse is the one bounded by a rectangle whose top-left corner is (x,y) and whose dimensions are width by height. The ellipse section starts a the angle start-radians (0 is three o'clock and half-pi is twelve o'clock) and continues to the angle end-radians; if counter-clockwise? is true, then the arc runs counter-clockwise from start-radians to end-radians, otherwise it runs clockwise.

If the path has no open sub-path, a new one is started with the arc's starting point. Otherwise, the arc extends the existing sub-path, and the existing path is connected with a line to the arc's starting point.

A path is not connected to any particular dc<%> object, so setting a dc<%> origin or scale does not affect path operations. Instead, a dc<%>'s origin and scale apply at the time that the path is drawn or used to set a region.

• (send a-dc-path arc x y width height start-radians end-radians counter-clockwise?) -> void
     x : real number
     y : real number
     width : non-negative real number
     height : non-negative real number
     start-radians : real number
     end-radians : real number
     counter-clockwise? = #t : boolean