draw-ellipse-sector

Generic Function

Package: common-graphics

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

Draws an ellipse sector on 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.) The ellipse is rotated so that the semi-major-axis makes angle semi-major-axis-angle with the x-axis passing through the center. Angles are measured clockwise. The portion of the ellipse drawn is the sector starting at start-angle (0 is the x axis when the center is the origin) through the length-angle. Again, angles are measured clockwise.

So, the ellipse created when specifying semi-major-axis 200, semi-minor-axis 10, and semi-major-axis-angle 5 is a long, thin ellipse, 400 pixels wide, with the long axis nearly horizontal, pointing to about 16 minutes after the hour (horizontal would be 15 minutes after the hour), centered at center. Now, if the start-angle of 0 and a length-angle of 90, all of the ellipse in the lower right quadrant is drawn, along with the lines from the ends of the arc to the center and no part is drawn in any other quadrant.

Note: incompatible change in release 6.0: in releases prior to 6.0, when a frame-with-single-child instance was passed to this operator, the operator was actually applied to the child (the result of applying frame-child to the frame-with-single-child instance). In release 6.0, this redirection no longer occurs. If you intend this operator to apply to the frame-child, pass that to this operator rather than the parent. This is a non-backward-compatible-change. See the release notes for more information.

Common Graphics and IDE documentation is described in About Common Graphics and IDE documentation in cgide.htm.

The documentation is described in introduction.htm and the index is in index.htm.

Created 2000.10.5.