When you project bodies to make sketch lines, shouldn’t the lines be locked? I think so.
You can’t lock the diameter of a circle unless you give it a dimension (or constraint). That means if you lock all of a sketch before adding new lines with constraints, the solver can still mess with it.
You can’t lock the control points of a fit-point spline. You can’t give them symmetry constraints either.
I think you should be able to give two points a horizontal/vertical constraint without drawing a line between them.
The solver does a bad job of reading my mind. When I add a constraint, it will try every possible way to satisfy it except the one I want. I know how dumb that sounds, but it must have some way of choosing between solutions, and I wonder about its biases. Try this:
Add a tangent constraint between the line and circle.
- First try, it moves the circle.
- Lock the center point. Second try, it shifts the line, keeping its length and orientation.
- Lock the free end of the line. Now it resizes the circle.
- Lock the circle’s diameter. Now it does what I expected.
Constraint-based drawing has always sounded a lot better than it works. I usually end up adding constraints just to place things, then removing them and locking everything to keep them there. Sometimes I miss the old 2D CAD approach with snap points and everything stays where you put it.