DialogueBox.cs

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

namespace MorganSS
{
    public class DialogueBox : MonoBehaviour
    {
        public static Message CurrentMessage;
        public static List<Message> MessageQueue = new List<Message>();

        public bool Showing => !(CurrentMessage is null);

        [SerializeField]
        private Sprite[] CharacterExpressions;
        [SerializeField]
        private Image Background;
        [SerializeField]
        private Image CharacterDisplay;
        [SerializeField]
        private TMP_Text TextField;
        [SerializeField]
        private int CharactersPerSecond = 20;

        private float TimeSinceTextStart;

        // Update is called once per frame
        void Update()
        {
            CharacterDisplay.enabled = Showing;
            Background.enabled = Showing;
            TextField.enabled = Showing;

            MessageQueue.RemoveAll(m => m is null);
            if (!Showing && MessageQueue.Count > 0)
            {
                CurrentMessage = MessageQueue[0];
                MessageQueue.RemoveAt(0);
            }

            if (!Showing) { return; }
            CharacterDisplay.sprite = CharacterExpressions.Where(
                s => s.name == (CurrentMessage.CharacterSpeaking + "_" + CurrentMessage.Expression).ToLower()).FirstOrDefault();
            CharacterDisplay.GetComponent<RectTransform>().sizeDelta = new Vector2(
                4.4f * CharacterDisplay.sprite.rect.width,
                4.4f * CharacterDisplay.sprite.rect.height);

            TimeSinceTextStart += Time.deltaTime;
            var charactersShouldShow = (int)(TimeSinceTextStart * CharactersPerSecond);
            charactersShouldShow = charactersShouldShow >= CurrentMessage.Text.Length ? CurrentMessage.Text.Length : charactersShouldShow;
            TextField.text = CurrentMessage.Text.Substring(0,charactersShouldShow);

            if (Input.GetKeyDown(KeyCode.C))
            {
                if (charactersShouldShow < CurrentMessage.Text.Length)
                {
                    TimeSinceTextStart = 1000f; // Longer time than any message would take to display
                }
                else
                {
                    CurrentMessage = null;
                    if (MessageQueue.Count > 0)
                    {
                        CurrentMessage = MessageQueue[0];
                        MessageQueue.RemoveAt(0);
                    }
                    TimeSinceTextStart = 0f;
                }
            }
        }
    }
}