erase-ellipse-arc

Arguments: stream center semi-major-axis semi-minor-axis semi-major-axis-angle start-angle length-angle

Erases an ellipse arc from stream. The ellipse is defined by the center (a position) and the two half-axes, lengths from the center to the farthest point on the edge and to the nearest point on the edge, called the semi-major-axis and the semi-minor-axis. (Technically, the major axis should be longer than the minor axis but the two arguments need not have that relationship.) Because the Windows ellipse drawer can only draw ellipses that are vertically or horizontally oriented, the semi-major-axis-angle argument must be a multiple of 90. Other values will signal an error. The argument specifies the angle between the semi-major-axis and a line parallel to the x-axis passing through the center. Angles are measured clockwise. The portion of the ellipse drawn is the arc starting at start-angle (0 is the x axis when the center is the origin) through the length-angle.

center should be a position (see make-position). stream should be a cg-stream.

Contrast with draw-ellipse-arc, which draws the ellipse on stream.

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Created 2019.8.20.