使用Win API点击Firefox右键菜单时菜单消失的问题求助

使用WinAPI的PostMessage发送WM_LBUTTONDOWN和WM_LBUTTONUP命令点击Firefox右键菜单时，菜单会立即消失，但在Chrome中测试无此问题。相关代码片段：

PostMessage(handle, WM_LBUTTONDOWN, 1, MakeLParam(lpPoint.X, lpPoint.Y)); // 右键菜单立即消失

完整测试代码如下：

using System;
using System.Runtime.InteropServices;
using System.Threading;

namespace TestClickByWinApi
{
    internal class Program
    {
        static void Main(string[] args)
        {
            while (true)
            {
                Console.WriteLine("=================");
                Console.WriteLine("Enter to continue");
                Console.ReadLine();

                Console.WriteLine("Start after 3s. Move cursor to the windows");
                Thread.Sleep(3000);

                // 获取鼠标当前屏幕坐标及窗口句柄
                GetCursorPos(out POINT lpPoint);
                var handle = WindowFromPoint(lpPoint);

                ScreenToClient(handle, ref lpPoint); // 将屏幕坐标转换为窗口客户端坐标

                // 模拟鼠标点击
                PostMessage(handle, WM_LBUTTONDOWN, 1, MakeLParam(lpPoint.X, lpPoint.Y)); // 按下左键，Firefox执行此命令后右键菜单消失
                PostMessage(handle, WM_LBUTTONUP, 1, MakeLParam(lpPoint.X, lpPoint.Y)); // 释放左键

                Console.WriteLine($"Click to handle={FormatIntPtr(handle)}, pos={lpPoint.X}, {lpPoint.Y}");
            }
        }

        static int MakeLParam(int x, int y)
        {
            return (y << 16) | (x & 0xFFFF);
        }

        static string FormatIntPtr(IntPtr handle)
        {
            return "0x" + handle.ToString("X").PadLeft(IntPtr.Size * 2, '0');
        }

        #region Const
        private const int WM_LBUTTONDOWN = 0x0201; // 按下左键
        private const int WM_LBUTTONUP = 0x0202;
        private const int WM_RBUTTONDOWN = 0x0204;
        private const int WM_RBUTTONUP = 0x0205;
        #endregion

        #region Win api
        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern bool PostMessage(IntPtr hWnd, int Msg, int wParam, int lParam);

        [DllImport("user32.dll")]
        static extern IntPtr WindowFromPoint(POINT point);

        [DllImport("user32.dll")]
        public static extern bool GetCursorPos(out POINT lpPoint);

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern bool ScreenToClient(IntPtr hWnd, ref POINT lpPoint);

        [StructLayout(LayoutKind.Sequential)]
        public struct POINT
        {
            public int X;
            public int Y;
        }
        #endregion
    }
}

1. 改用SendInput模拟硬件级鼠标操作 #

PostMessage仅将消息投递到窗口队列，Firefox的菜单系统可能会验证输入真实性，而SendInput模拟真实硬件鼠标输入，更不易被拦截或判定为非用户操作，是最可靠的解决方案。

步骤： #

1. 添加SendInput相关API定义：

#region SendInput 相关定义
[StructLayout(LayoutKind.Sequential)]
struct INPUT
{
    public uint Type;
    public MOUSEKEYBDHARDWAREINPUT Data;
}

[StructLayout(LayoutKind.Explicit)]
struct MOUSEKEYBDHARDWAREINPUT
{
    [FieldOffset(0)]
    public MOUSEINPUT Mouse;
}

[StructLayout(LayoutKind.Sequential)]
struct MOUSEINPUT
{
    public int X;
    public int Y;
    public uint MouseData;
    public uint Flags;
    public uint Time;
    public IntPtr ExtraInfo;
}

private const uint INPUT_MOUSE = 0;
private const uint MOUSEEVENTF_LEFTDOWN = 0x0002;
private const uint MOUSEEVENTF_LEFTUP = 0x0004;
private const uint MOUSEEVENTF_MOVE = 0x0001;
private const uint MOUSEEVENTF_ABSOLUTE = 0x8000;

[DllImport("user32.dll", SetLastError = true)]
private static extern uint SendInput(uint nInputs, INPUT[] pInputs, int cbSize);
#endregion

2. 编写模拟点击方法：

static void SimulateMouseClick(POINT screenPoint)
{
    // 转换为SendInput要求的绝对坐标（范围0-65535）
    int x = (screenPoint.X * 65535) / System.Windows.Forms.Screen.PrimaryScreen.Bounds.Width;
    int y = (screenPoint.Y * 65535) / System.Windows.Forms.Screen.PrimaryScreen.Bounds.Height;

    INPUT[] inputs = new INPUT[3];

    // 移动鼠标到目标位置
    inputs[0].Type = INPUT_MOUSE;
    inputs[0].Data.Mouse.X = x;
    inputs[0].Data.Mouse.Y = y;
    inputs[0].Data.Mouse.Flags = MOUSEEVENTF_MOVE | MOUSEEVENTF_ABSOLUTE;

    // 按下左键
    inputs[1].Type = INPUT_MOUSE;
    inputs[1].Data.Mouse.Flags = MOUSEEVENTF_LEFTDOWN;

    // 释放左键
    inputs[2].Type = INPUT_MOUSE;
    inputs[2].Data.Mouse.Flags = MOUSEEVENTF_LEFTUP;

    SendInput((uint)inputs.Length, inputs, Marshal.SizeOf(typeof(INPUT)));
}

3. 替换原PostMessage代码：

// 保留获取屏幕坐标的代码，不需要转换为客户端坐标
GetCursorPos(out POINT lpPointScreen);
// 替换原有PostMessage调用
SimulateMouseClick(lpPointScreen);

2. 确保获取右键菜单的正确句柄 #

WindowFromPoint可能返回Firefox主窗口而非右键菜单窗口，右键菜单是弹出式窗口，可尝试获取前台窗口：

[DllImport("user32.dll")]
static extern IntPtr GetForegroundWindow();

// 在右键菜单弹出后，替换handle获取逻辑
var handle = GetForegroundWindow();

3. 补充完整鼠标消息序列（仅作为备选） #

若坚持使用PostMessage，需补充完整交互流程，模拟真实鼠标移动后再点击：

// 先发送鼠标移动消息到目标位置
PostMessage(handle, WM_MOUSEMOVE, 0, MakeLParam(lpPoint.X, lpPoint.Y));
Thread.Sleep(10); // 短暂延迟模拟真实操作
// 发送按下和释放消息
PostMessage(handle, WM_LBUTTONDOWN, 1, MakeLParam(lpPoint.X, lpPoint.Y));
Thread.Sleep(10);
PostMessage(handle, WM_LBUTTONUP, 1, MakeLParam(lpPoint.X, lpPoint.Y));

注：此方法仍可能被Firefox拦截，优先推荐SendInput方案。

内容的提问来源于stack exchange，提问作者Ohia