A circle just an ellipse with equal graphical<-width
and graphical<-height.
It's border-line may have a graphical<-texture
and graphical<-pen.
The circle's interior may be filled with a colour using circle->fill.
|{foreground,background}*<-fill
equals @nil.
Defaults: @nil (transparent).
<-diameter<-width
or graphical<-height
is specified this value is used for both parameters. If both are
specified the minimum of the two is used for both.<-device
coordinate system — lies inside the circle: (X-cx)² + (Y-cy)² ≤
r². Bbox corners just miss.
Same test drives graphical->in_event_area;
that method additionally inflates the radius by event_tolerance
pixels so hits within tolerance of the outline still count.
<-radius<-width and graphical<-height
to this value. See also circle->radius.<-width. circle->radius
sets graphical<-width and graphical<-height
to twice the argument.