Angle and position from two nodes

[l0uisgrange]

Hi CeTZ team 👋,

I'm currently building a library using CeTZ to draw electronic circuits, and I'm planning to contribute back to CeTZ once the library is published to Typst Universe 🚀.

I currently have something like this:

#let component(node, node2, ..things) = {
    group(name: uid, {
        let angle = get-angle(rotate, node, node2)
        cetz.draw.on-layer(1, {
            (draw.anchors)(..things)
            cetz.draw.scope({
                cetz.draw.set-origin("center")
                cetz.draw.scale(scale)
                cetz.draw.rotate(angle)
                (draw.component)(..things)
            })
        })
        // ...
    })
}

With my function get-angle

#let get-angle(rotate, node, node2) = {
    if (node2 != none) {
        return calc.atan2(node2.at(0) - node.at(0), node2.at(1) - node.at(1))
    } else {
        return rotate
    }
}

1. However, I need a reliable way to compute the angle between two nodes, whether they’re anchors or coordinates (x, y). The problem is that the code above doesn't work with anchors. I’ve looked into get-ctx, but I’m not sure that’s the right approach.
2. Why isn't the "center" anchor available when I try to use it? It seems like it's never defined inside the group. How can I access it properly?

Thanks in advance for your help! 😊

[johannes-wolf]

👋 Hi :)

1. You have to call let (ctx, vec) = coordinate.resolve(ctx, node) to resolve any cetz coordinate to a vector. Here is an example: https://github.com/cetz-package/cetz/blob/master/src/lib/angle.typ#L66
2. The groups anchors are not available inside the group itself, bout outside of it. But you can nest groups, if you want go get some inner center anchor.

I hope that helps.