src/constraints/distance_constraint.cpp

#include "rive/constraints/distance_constraint.hpp"
#include "rive/bones/bone.hpp"
#include "rive/artboard.hpp"
#include <algorithm>

using namespace rive;

enum class Mode { Closer = 0, Further = 1, Exact = 2 };

void DistanceConstraint::constrain(TransformComponent* component) {
    if (m_Target == nullptr) {
        return;
    }

    Vec2D targetTranslation;
    m_Target->worldTranslation(targetTranslation);

    Vec2D ourTranslation;
    component->worldTranslation(ourTranslation);

    Vec2D toTarget;
    Vec2D::subtract(toTarget, ourTranslation, targetTranslation);
    float currentDistance = Vec2D::length(toTarget);
    switch (static_cast<Mode>(modeValue())) {
        case Mode::Closer:
            if (currentDistance < distance()) {
                return;
            }
            break;
        case Mode::Further:
            if (currentDistance > distance()) {
                return;
            }
            break;
        default:
            break;
    }
    if (currentDistance < 0.001f) {
        return;
    }

    Vec2D::scale(toTarget, toTarget, 1.0f / currentDistance);
    Vec2D::scale(toTarget, toTarget, distance());

    Mat2D& world = component->mutableWorldTransform();
    Vec2D position;
    Vec2D::add(position, targetTranslation, toTarget);
    Vec2D::lerp(position, ourTranslation, position, strength());
    world[4] = position[0];
    world[5] = position[1];
}