erase-contents-ellipse-sector

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

Erases (i.e. replaces with the background color or texture) the specified filled ellipse-sector from stream. An ellipse-sector is an ellipse-arc with the endpoints of the arc connected to the center of the ellipse, like a piece of an elliptical pie.

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.

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

Contrast with fill-ellipse-sector which draws the filled ellipse-sector on stream.

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Created 2019.8.20.