I am working on a Unity tool and I want to create a custom GUI for it.

In this simple script, I am checking if the mouse has hovered over a button and if so I change a GUI color. This is just a really basic example, but the same principles apply to something that I want to make.

The problem is that the change is really delayed. I tried implementing isDirty state, where it only repaints when it needs to. Although it doesn't seem to work. Same delay issue... I could just repaint the window every frame, but that is really non-performant.

private bool isDirty = false;

Rect _hoveredRect;
Rect HoveredRect
{
    get { return _hoveredRect; }
    set
    {
        if (_hoveredRect != value)
        {
            isDirty = true;
        }
        _hoveredRect = value;
    }
}

void Update()
{
    if (isDirty)
    {
        Repaint();
        isDirty = false;
    }
}
void OnGUI()
{
    Rect button = new Rect(25, 25, 100, 35);
    DrawButton(button, "Label");
}
bool DrawButton(Rect rect, string label)
{
    var e = Event.current;
    bool hovered = rect.Contains(e.mousePosition);

    if (hovered)
    {
        HoveredRect = rect;
    }
    if (!hovered && HoveredRect == rect)
    {
        HoveredRect = Rect.zero;
    }

    var defaultColor = GUI.color;

    GUI.color = hovered ? Color.red : defaultColor;

    bool pressed = GUI.Button(rect, label);

    GUI.color = defaultColor;

    return pressed;
}

Then I came up with another solution, which should work, but I need to get mouse position and I can't use Event.current outside of OnGUI function.

Dictionary<Rect, bool> hoverableRects = new Dictionary<Rect, bool>();

private void OnEnable()
{
    EditorApplication.update += UpdateMe;
}
private void OnDisable()
{
    EditorApplication.update -= UpdateMe;
}

void UpdateMe()
{
    var mousePos = ??; List<Rect> rects = new List<Rect>(hoverableRects.Keys);
    foreach (var rect in rects)
    {
        hoverableRects[rect] = rect.Contains(mousePos);
    }
}
void OnGUI()
{
    Rect button = new Rect(25, 25, 100, 35);
    DrawButton(button, "Label");
}
bool DrawButton(Rect rect, string label)
{
    if (!hoverableRects.ContainsKey(rect))
    { hoverableRects.Add(rect, false); }

    var defaultColor = GUI.color;

    GUI.color = hoverableRects[rect] ? Color.red : defaultColor;

    bool pressed = GUI.Button(rect, label);

    GUI.color = defaultColor;

    return pressed;
}

Is there a way to get mouse position every frame outside the OnGUI method?