notify/Notify/Interop/WindowActivator.cs

using System;

namespace Notify.Interop;

/// <summary>
/// 把目标窗口拉回前台
///
/// Windows 限制后台进程抢焦点，这里用一套组合技绕过：ALT 键模拟 +
/// AttachThreadInput 把当前线程与前台/目标线程的输入队列挂接 +
/// SetWindowPos/BringWindowToTop/SwitchToThisWindow/SetForegroundWindow 多管齐下
/// </summary>
public static class WindowActivator
{
    public static bool Activate(IntPtr hwnd)
    {
        if (hwnd == IntPtr.Zero || !Win32.IsWindow(hwnd))
        {
            return false;
        }

        try
        {
            // 最小化的先还原
            if (Win32.IsIconic(hwnd))
            {
                Win32.ShowWindow(hwnd, Win32.SW_RESTORE);
            }

            var foreground = Win32.GetForegroundWindow();
            var curThread = Win32.GetCurrentThreadId();
            var fgThread = Win32.GetWindowThreadProcessId(foreground, out _);
            var targetThread = Win32.GetWindowThreadProcessId(hwnd, out _);

            // 模拟一次 ALT 抬起，满足 Windows 的"防焦点抢占"前置条件
            Win32.keybd_event(Win32.VK_MENU, 0, 0, IntPtr.Zero);
            Win32.keybd_event(Win32.VK_MENU, 0, Win32.KEYEVENTF_KEYUP, IntPtr.Zero);

            if (fgThread != curThread)
            {
                Win32.AttachThreadInput(curThread, fgThread, true);
            }

            if (targetThread != curThread && targetThread != fgThread)
            {
                Win32.AttachThreadInput(curThread, targetThread, true);
            }

            Win32.AllowSetForegroundWindow(Win32.ASFW_ANY);
            Win32.SetWindowPos(hwnd, IntPtr.Zero, 0, 0, 0, 0, Win32.SWP_NOMOVE | Win32.SWP_NOSIZE | Win32.SWP_SHOWWINDOW);
            Win32.BringWindowToTop(hwnd);
            Win32.SwitchToThisWindow(hwnd, true);
            Win32.SetForegroundWindow(hwnd);
            Win32.ShowWindow(hwnd, Win32.SW_SHOW);

            if (targetThread != curThread && targetThread != fgThread)
            {
                Win32.AttachThreadInput(curThread, targetThread, false);
            }

            if (fgThread != curThread)
            {
                Win32.AttachThreadInput(curThread, fgThread, false);
            }

            return Win32.GetForegroundWindow() == hwnd;
        }
        catch
        {
            return false;
        }
    }
}