Aetheria/Assets/Scripts/UI/DropdownMenu.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using TMPro;
using UnityEngine;
using UnityEngine.UI;

public class DropdownMenu : MonoBehaviour
{
    public Canvas Canvas;
    public ClickCatcher CancelClickCatcher;
    public PropertyButton OptionPrefab;

    public RectTransform ContentRoot;

    public float OptionHeight;
    public float PaddingHeight;
    
    private List<GameObject> _options = new List<GameObject>();

    private void Start()
    {
        if (CancelClickCatcher != null)
            CancelClickCatcher.OnClick += data =>
            {
                End();
            };
    }

    private void End()
    {
        CancelClickCatcher.gameObject.SetActive(false);
        gameObject.SetActive(false);
    }

    public void Clear()
    {
        // Destroy previous options
        foreach(var option in _options)
            Destroy(option);
        _options.Clear();
    }

    public void AddOption(string text, Action action, bool selected = false, bool enabled = true)
    {
        var optionButton = Instantiate(OptionPrefab, ContentRoot);
        optionButton.Label.text = text;
        optionButton.Button.OnClick += data =>
        {
            action();
            End();
        };
        optionButton.Button.CurrentState = !enabled ? FlatButtonState.Disabled : selected ? FlatButtonState.Selected : FlatButtonState.Unselected;
        _options.Add(optionButton.gameObject);
    }

    public void Show(RectTransform parent)
    {
        var rect = transform as RectTransform;
        var pivot = rect.pivot;
        pivot.x = 0;
        var scaleFactor = Canvas.scaleFactor;
        var corners = new Vector3[4];
        parent.GetWorldCorners(corners);
        var pivotTop = corners[0].y > (PaddingHeight + _options.Count * OptionHeight) * scaleFactor;
        pivot.y = pivotTop ? 1 : 0;
        rect.pivot = pivot;
        rect.sizeDelta = parent.sizeDelta;
        rect.position = pivotTop ? corners[0] : corners[1];
        CancelClickCatcher.gameObject.SetActive(true);
    }
}