Select end of textField in Unity Editor

using System.Reflection;
using UnityEditor;
using UnityEngine;

class TestEditor : EditorWindow
{
    [MenuItem("Test/" + _Title)]
    static void ShowWindow() { GetWindow(typeof(TestEditor), false, _Title); }
    const string _Title = "TextEditor";

    string _txt = "Some text long 1 22 333 4444 55555 666666 7777777 END";
    bool _focusOnTextRequested;

    void OnGUI()
    {
        GUI.SetNextControlName("testText");
        EditorGUILayout.TextField(_txt, EditorStyles.textField);
        float textFieldW = GUILayoutUtility.GetLastRect().width;
        if (_focusOnTextRequested) {
            switch (Event.current.type) {
            case EventType.Layout:
                EditorGUI.FocusTextInControl("testText");
                break;
            case EventType.Repaint:
                _focusOnTextRequested = false;
                TextEditor tEditor = GetCurrTextEditor();
                if (tEditor == null) Debug.LogWarning("Couldn't get TextEditor " + Event.current.type);
                else {
                    float txtW = EditorStyles.textField.CalcSize(new GUIContent(_txt)).x;
                    tEditor.selectIndex = _txt.Length - 3;
                    tEditor.cursorIndex = _txt.Length;
                    if (textFieldW < txtW) {
                        tEditor.scrollOffset = new Vector2(txtW - textFieldW, 0);
                    }
                    Repaint();
                }
                break;
            }
        }

        if (GUILayout.Button("Select end")) {
            // EditorGUI.FocusTextInControl("testText"); // THID DOESN'T WORK
            _focusOnTextRequested = true;
        }
    }

    TextEditor GetCurrTextEditor()
    {
        return typeof(EditorGUI)
            .GetField("activeEditor", BindingFlags.Static | BindingFlags.NonPublic)
            .GetValue(null) as TextEditor;
    }
}