Unityでマルチディスプレイ対応/メインディスプレイはWindow表示でResize可能

DisplayScript.cs

using UnityEngine;

public class DisplayScript : MonoBehaviour
{
    void Start()
    {
        Debug.Log("displays connected: " + Display.displays.Length);

        Display.displays[0].Activate();
        Display.displays[1].Activate();

        ////Secondary Displayの解像度設定（タイトルバー隠す）
        Invoke("DelayWindow", 0f);
    }

    private void DelayWindow()
    {
        WindowController.windowReplace(Application.productName, 100, 100, 640, 480, false);
        WindowController.windowReplace("Unity Secondary Display", 2560, 0, 3840, 2160, true);
    }
}

WindowController.cs

using System;
using System.Runtime.InteropServices;

public static class WindowController
{
    [DllImport("user32.dll", EntryPoint = "SetWindowPos")]
    private static extern bool SetWindowPos(IntPtr hWnd, int hWndInsertAfter, int x, int Y, int cx, int cy, int wFlags);

    [DllImport("user32.dll", EntryPoint = "FindWindow")]
    public static extern IntPtr FindWindow(System.String className, System.String windowName);

    // Sets window attributes
    [DllImport("user32.dll")]
    public static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

    // Gets window attributes
    [DllImport("user32.dll")]
    public static extern int GetWindowLong(IntPtr hWnd, int nIndex);

    // assorted constants needed
    public static int GWL_STYLE = -16;
    public static int WS_CHILD = 0x40000000; //child window
    public static int WS_BORDER = 0x00800000; //window with border
    public static int WS_DLGFRAME = 0x00400000; //window with double border but no title
    public static int WS_SIZEBOX = 0x00040000; //window with double border but no title
    public static int WS_SYSMENU = 0x00080000; //window with double border but no title

    public static int WS_CAPTION = WS_BORDER | WS_DLGFRAME; //window with a title bar

    public static void windowReplace(string name, int x, int y, int width, int height, bool hideTitleBar)
    {
        var window = FindWindow(null, name);

        if (hideTitleBar)
        {
            int style = GetWindowLong(window, GWL_STYLE);
            SetWindowLong(window, GWL_STYLE, (style & ~WS_CAPTION));
        }
        else
        {
            int style = GetWindowLong(window, GWL_STYLE);
            style |= WS_CAPTION ;   //show title bar
            style |= WS_SIZEBOX;    //Resizable window
            style |= WS_SYSMENU;    //Show Close button
            SetWindowLong(window, GWL_STYLE, style);
        }

        SetWindowPos(window, 0, x, y, width, height, width * height == 0 ? 1 : 0);
    }
}