ISupportsOverlays

Description

Implement this interface to enable overlays in the EditorWindow.

When ISupportsOverlays is implemented, an Overlay Canvas is automatically added to the VisualElement tree for your EditorWindow. OverlayAttribute will now be able to specify this window type as a valid target for registering an Overlay.

using System;
using UnityEditor;
using UnityEditor.Overlays;
using UnityEngine;
using UnityEngine.UIElements;

class EditorWindowOverlayExample : EditorWindow, ISupportsOverlays
{
    [MenuItem("Window/Overlay Supported Window Example")]
    static void Init() => GetWindow<EditorWindowOverlayExample>();

    void OnGUI()
    {
        GUILayout.Label("Here is some text");
        GUILayout.FlexibleSpace();
        GUILayout.Label("Plus some more text, but on the bottom of the screen.");
    }
}

[Overlay(typeof(EditorWindowOverlayExample), "Is Mouse Hovering Me?", true)]
class IsMouseHoveringMe : Overlay
{
    Label m_MouseLabel;

    public override VisualElement CreatePanelContent()
    {
        m_MouseLabel = new Label();
        m_MouseLabel.style.minHeight = 40;
        m_MouseLabel.RegisterCallback<MouseEnterEvent>(evt => m_MouseLabel.text = "Mouse is hovering this Overlay content!");
        m_MouseLabel.RegisterCallback<MouseLeaveEvent>(evt => m_MouseLabel.text = "Mouse is not hovering this Overlay content.");
        return m_MouseLabel;
    }
}