feilong-client/Assets/Scripts/Framework/Editor/EditorNavigation/APINavigation.cs

using UnityEditor;
using UnityEngine;
using UnityToolbarExtender;

[InitializeOnLoad]
class APINavigation : INavigation
{
    public int Order => 50;

    static APINavigation()
    {
        ToolbarExtender.AddToLeft(new APINavigation());
    }

    public void OnGUI()
    {
        EditorGUI.BeginDisabledGroup(Application.isPlaying);
        if (GUILayout.Button("Unity API", ToolbarStyles.apiButtonStyle))
        {
            Application.OpenURL("https://docs.unity.cn/cn/current/Manual/index.html");
        }
        EditorGUI.EndDisabledGroup();
    }
    static class ToolbarStyles
    {
        public static readonly GUIStyle apiButtonStyle;

        static ToolbarStyles()
        {
            apiButtonStyle = new GUIStyle("Command")
            {
                fixedWidth = 80,
                fontSize = 13,
                alignment = TextAnchor.MiddleCenter,
                imagePosition = ImagePosition.ImageAbove,
                fontStyle = FontStyle.Bold
            };
        }
    }
}