You can enlarge video to the window size

app.js

// ==UserScript==
// @name         dtv in fullWindow
// @namespace    https://marco.plus/
// @version      0.1
// @description  You can enlarge video to the window size.
// @author       Marco
// @match        https://pc.video.dmkt-sp.jp/*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    class DtvInFullWindow{
        constructor(){
            let insertLocation = document.querySelector(".fullscreen");
            let button = document.createElement("button");
            let buttonWrapper = document.createElement("div");
            button.textContent = "Fit Window";
            button.addEventListener("click",()=>{
                this.enlarge(document.querySelector(".titleDetailPlayer"));
            });
            buttonWrapper.appendChild(button);
            insertLocation.insertAdjacentElement('beforebegin',buttonWrapper);
        }
        enlarge(elm){
            elm.style.width="100%";
        }
    }
    let elm = document.querySelector(".actionOverlayContentIcon--play");
    if(elm !== null){
        elm.addEventListener("click",()=>{
            let intervalId = setInterval(()=>{
                if(document.querySelector(".fullscreen")!==null){
                    clearInterval(intervalId);
                    let dtvInFullWindow = new DtvInFullWindow();
                }
            },500);
        });
    }
})();

【既知のバグ】

• 体感3~4割くらいで何故か動かない