Thanks guys!!

Do you have this in your git repo just to have a look at?

Not yet. At this stage it is still way too early. I am planning to release it when the implementation starts making sense. This would allow to debug and also get feedback from you guys.

Aren't ellipses usually defined by three points and then use distance constraints to determine major and minor axes and rotation?

Well, to be honest with you my trigonometry knowledge is very rusted, but I think that an Ellipse should have 5 degrees of freedom (I see this as x,y of both focuses+constraint on distance to both focuses from any point = major diameter, 2*2+1=5). Those 3 points can not be any 3 points, or you would have infinite solutions. You might start adding "constraints" to those points, (that one is on the major axis, for example)...

... There are many possible methods (and I welcome suggestions). My best option at this moment is, center point, point defining the major axis (with respect to the center point), so this is also the major radius, and then as third point, a point the ellipse must go through...

I guess there will be also an ellipse arc too for adding an angle constraint.

I plan to do it, but that is a next step.

I guess there will be also an ellipse arc too for adding an angle constraint.

That is part of the "maybe I do not manage to do it"

At this moment the constraints dealing with the center of the ellipse seem to work (This is the same as in a Circle, so the code was there). The challenge is the constraints applying to the edge. Oh, well, first I need to make the basics work and then I will focus on the rest...