HTML5 Canvas's Arc function diagram

In the case where the coordinate system is not transformed, the ARC function arcs in the direction shown:

For example, Arc (X,y,r,math.pi/6,math.pi/3,false), is the X, y as the center, R is the radius, from the x positive axis clockwise 30 degrees from the starting angle, to the x positive axis clockwise 60 degrees for the end angle arc painting;

Arc (x,y,r,math.pi/4,math.pi/2,true), is x, y as the center, R is the radius, from the x positive axis counterclockwise 45 degrees is the starting angle, to the x positive axis clockwise 90 degrees for the end angle arc.

HTML5 Canvas's Arc function diagram