c# - 为什么 SetWinEventHook with EVENT_OBJECT_LOCATIONCHANGE 在鼠标移动时触发？

Question

我在进程上创建了一个 Hook ，以便在其窗口移动时进行注册。我使用事件常量 EVENT_OBJECT_LOCATIONCHANGE，根据 MSDN

An object has changed location, shape, or size. The system sends this event for the following user interface elements: caret and window objects. Server applications send this event for their accessible objects.

它有效，但它也会在简单的鼠标悬停在应用程序上时触发。谁能解释一下为什么？

这里是一个重现它的例子:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    static class NativeMethods
    {
        [DllImport("user32.dll")]
        public static extern System.IntPtr SetWinEventHook(uint eventMin, uint eventMax, System.IntPtr hmodWinEventProc, WinEventDelegate lpfnWinEventProc, uint idProcess, uint idThread, uint dwFlags);

        public delegate void WinEventDelegate(System.IntPtr hWinEventHook, uint eventType, System.IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime);
    }

    public partial class Form1 : Form
    {
        private const uint WINEVENT_OUTOFCONTEXT = 0x0000;
        private const uint EVENT_OBJECT_LOCATIONCHANGE = 0x800B;

        public Form1()
        {
            InitializeComponent();
            int processId = Process.GetCurrentProcess().Id;

            NativeMethods.SetWinEventHook(EVENT_OBJECT_LOCATIONCHANGE, EVENT_OBJECT_LOCATIONCHANGE, System.IntPtr.Zero, WinEventProc, (uint)processId, (uint)0, WINEVENT_OUTOFCONTEXT);
        }

        private void WinEventProc(System.IntPtr hWinEventHook, uint eventType, System.IntPtr hwnd, int idObject, int idChild, uint dwEventThread, uint dwmsEventTime)
        {
           if (hwnd == IntPtr.Zero)
            {
                Debug.WriteLine("Mouse moved");
            }
            else
            {
                Debug.WriteLine("Location changed");
            }
        }
    }
}

Answer 1

头文件 WinUser.h 有关于 EVENT_OBJECT_LOCATIONCHANGE 的说明:

 * Note also that USER will generate LOCATIONCHANGE notifications for two
 * non-window sys objects:
 *      (1) System caret
 *      (2) Cursor

这解释了为什么当光标移动时会触发该事件。

正如 Hans 在他的评论中所说，只需按 OBJID_CURSOR 过滤对象 ID。