Testing Scroll Bug

using System.Collections.Generic;
using UnityEditor;
using UnityEngine;

// This class must be placed in an Editor Folder
public class TestScrollBugWindow : EditorWindow
{
    List<string> m_list;
    Vector2 m_scrollPosition;

    const int ITEMS_COUNT = 1000;
    readonly float ITEM_HEIGHT = EditorGUIUtility.singleLineHeight;

    [MenuItem("Window/Test Scroll Bug")]
    internal static void Open()
    {
        TestScrollBugWindow window = GetWindow<TestScrollBugWindow>();
        window.titleContent = new GUIContent("TestScrollBug");
        window.Show();
        window.Focus();
    }

    void OnEnable()
    {
        m_list = new List<string>(ITEMS_COUNT);
        for (int i = 0; i < ITEMS_COUNT; i++)
            m_list.Add(i.ToString());
    }

    void OnGUI()
    {
        Rect positionRect = new Rect(0, 0, position.width, position.height);

        // calculate view rect
        Rect viewRect = positionRect;
        viewRect.height = 16 * m_list.Count;
        viewRect.width -= 16; // rest the vertical scroll bar width to not to show the

        m_scrollPosition = GUI.BeginScrollView(positionRect, m_scrollPosition, viewRect, false, true);
        {
            float positionY = 0; // used to calculate the y position of each key
            for (int i = 0; i < m_list.Count; i++)
            {
                Rect rect = new Rect(0, positionY, viewRect.width, EditorGUIUtility.singleLineHeight);
                positionY += ITEM_HEIGHT;

                if (ElementRectOverlapsWithScrollViewRect(rect, positionRect))
                {
                    // DelayedTextField copy the text
                    m_list[i] = EditorGUI.DelayedTextField(rect, m_list[i]);

                    // TextField do not copy the text
                    // m_list[i] = EditorGUI.TextField(rect, m_list[i]);

                    // log to the console the names of the drawn elements to see if are equal to the names visible in the window
                    // Debug.Log("drawn: " + m_list[i]);
                }
            }
        }
        GUI.EndScrollView();
    }

    /// <summary> Calculate the global rect for the element and returns true if it overlaps with the scrollPositionRect. </summary>
    bool ElementRectOverlapsWithScrollViewRect(Rect elementRect, Rect scrollPositionRect)
    {
        Rect globalRect = elementRect;
        globalRect.y -= m_scrollPosition.y; // rest the scroll position

        return scrollPositionRect.Overlaps(globalRect);
    }
}