ET9_WebGL_Dev/Packages/cn.etetet.yiuiframework/Editor/Toolbar/YIUIToolbarCallback.cs

using System;
using UnityEngine;
using UnityEditor;
using System.Reflection;

#if UNITY_2019_1_OR_NEWER
using UnityEngine.UIElements;

#else
using UnityEngine.Experimental.UIElements;
#endif

namespace YIUIFramework.Editor
{
    public static class YIUIToolbarCallback
    {
        static Type m_toolbarType = typeof(UnityEditor.Editor).Assembly.GetType("UnityEditor.Toolbar");
        static Type m_guiViewType = typeof(UnityEditor.Editor).Assembly.GetType("UnityEditor.GUIView");
        #if UNITY_2020_1_OR_NEWER
        static Type m_iWindowBackendType = typeof(UnityEditor.Editor).Assembly.GetType("UnityEditor.IWindowBackend");

        static PropertyInfo m_windowBackend = m_guiViewType.GetProperty("windowBackend",
            BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);

        static PropertyInfo m_viewVisualTree = m_iWindowBackendType.GetProperty("visualTree",
            BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
        #else
		static PropertyInfo m_viewVisualTree = m_guiViewType.GetProperty("visualTree",
			BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);
        #endif
        static FieldInfo m_imguiContainerOnGui = typeof(IMGUIContainer).GetField("m_OnGUIHandler",
            BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);

        static ScriptableObject m_currentToolbar;
        public static Action OnToolbarGUI;
        public static Action OnToolbarGUILeft;
        public static Action OnToolbarGUIRight;

        static YIUIToolbarCallback()
        {
            EditorApplication.update -= OnUpdate;
            EditorApplication.update += OnUpdate;
        }

        static void OnUpdate()
        {
            if (m_currentToolbar == null)
            {
                var toolbars = Resources.FindObjectsOfTypeAll(m_toolbarType);
                m_currentToolbar = toolbars.Length > 0 ? (ScriptableObject)toolbars[0] : null;
                if (m_currentToolbar != null)
                {
                    #if UNITY_2021_1_OR_NEWER
                    var root = m_currentToolbar.GetType().GetField("m_Root", BindingFlags.NonPublic | BindingFlags.Instance);
                    var rawRoot = root.GetValue(m_currentToolbar);
                    var mRoot = rawRoot as VisualElement;
                    RegisterCallback("ToolbarZoneLeftAlign", OnToolbarGUILeft);
                    RegisterCallback("ToolbarZoneRightAlign", OnToolbarGUIRight);

                    void RegisterCallback(string root, Action cb)
                    {
                        var toolbarZone = mRoot.Q(root);

                        var parent = new VisualElement()
                        {
                            style =
                            {
                                flexGrow = 1,
                                flexDirection = FlexDirection.Row,
                            }
                        };
                        var container = new IMGUIContainer();
                        container.style.flexGrow = 1;
                        container.onGUIHandler += () => { cb?.Invoke(); };
                        parent.Add(container);
                        toolbarZone.Add(parent);
                    }
                    #else
                    #if UNITY_2020_1_OR_NEWER
					var windowBackend = m_windowBackend.GetValue(m_currentToolbar);

					// Get it's visual tree
					var visualTree = (VisualElement) m_viewVisualTree.GetValue(windowBackend, null);
                    #else
					// Get it's visual tree
					var visualTree = (VisualElement) m_viewVisualTree.GetValue(m_currentToolbar, null);
                    #endif

					// Get first child which 'happens' to be toolbar IMGUIContainer
					var container = (IMGUIContainer) visualTree[0];

					// (Re)attach handler
					var handler = (Action) m_imguiContainerOnGui.GetValue(container);
					handler -= OnGUI;
					handler += OnGUI;
					m_imguiContainerOnGui.SetValue(container, handler);

                    #endif
                }
            }
        }

        static void OnGUI()
        {
            OnToolbarGUI?.Invoke();
        }
    }
}