#include <windows.h>
#include <tchar.h>
#include <stdio.h>
#include <richedit.h>

struct ProcessWindow
{
    DWORD dwProcessId;
    HWND hwndWindow;
};

// 查找进程主窗口的回调函数
BOOL CALLBACK EnumWindowCallBack(HWND hWnd, LPARAM lParam)
{
    ProcessWindow* pProcessWindow = (ProcessWindow*)lParam;

    DWORD dwProcessId;
    GetWindowThreadProcessId(hWnd, &dwProcessId);

    // 判断是否是指定进程的主窗口
    if (pProcessWindow->dwProcessId == dwProcessId && IsWindowVisible(hWnd) && GetParent(hWnd) == NULL)
    {
        pProcessWindow->hwndWindow = hWnd;

        return FALSE;
    }

    return TRUE;
}

HWND CreateMyProcess()
{
    // 进程启动信息
    STARTUPINFO si;
    memset(&si, 0, sizeof(STARTUPINFO));
    si.cb = sizeof(STARTUPINFO);
    si.dwFlags = STARTF_USESHOWWINDOW;
    si.wShowWindow = SW_SHOW;

    // 进程信息
    PROCESS_INFORMATION pi;

    // 创建进程
    // 第二个参数是要启动的应用程序路径名，比如：C:/Test.exe
    TCHAR sz[] = _T(".\\wordpad_oldversion.exe");
    if (CreateProcess(NULL, sz, NULL, NULL, false, 0, NULL, NULL, &si, &pi))
    {
        ProcessWindow procwin;
        procwin.dwProcessId = pi.dwProcessId;
        procwin.hwndWindow = NULL;

        // 等待新进程初始化完毕
        WaitForInputIdle(pi.hProcess, 5000);

        // 查找主窗口
        EnumWindows(EnumWindowCallBack, (LPARAM)&procwin);

        return procwin.hwndWindow;
    }
    return NULL;
}

HWND GetFocusedChild(HWND wnd)
{
    DWORD SelfThreadId = GetCurrentThreadId();//获取本身的线程ID
    DWORD TargetThreadId = GetWindowThreadProcessId(wnd, NULL);//根据窗口句柄获取线程ID
    AttachThreadInput(TargetThreadId, SelfThreadId, true);//附加线程
    HWND child_wnd = GetFocus();//获取具有输入焦点的窗口句柄
    AttachThreadInput(TargetThreadId, SelfThreadId, false);//取消附加的线程
    return child_wnd;
}

int WINAPI WinMain(
    HINSTANCE hThisInst,
    HINSTANCE hPrevInst,
    LPSTR lpszCmdLine,
    int nCmdShow)
{
    ShowWindow(GetConsoleWindow(), SW_HIDE);

    HWND main_wnd = CreateMyProcess();
    HWND child_wnd = GetFocusedChild(main_wnd);

    COLORREF eye_color = 0x00cfe8cc;
    SendMessage(child_wnd, EM_SETBKGNDCOLOR, 0, eye_color);
    Sleep(200);

    HDC hDC = GetDC(child_wnd);
    SetBkMode(hDC, TRANSPARENT);
    SetTextColor(hDC, 0x000000cc);

    HFONT hFont = CreateFont
    (
        72, 0,                    // 高度40, 宽取0表示由系统选择最佳值
        0, 0,                    // 文本倾斜，与字体倾斜都为0
        FW_BOLD/*FW_NORMAL*/,
        0, 0, 0,                // 斜体，下划线，无中划线
        GB2312_CHARSET,            // 字符集
        OUT_DEFAULT_PRECIS,
        CLIP_DEFAULT_PRECIS,
        DEFAULT_QUALITY,        // 一系列的默认值
        DEFAULT_PITCH | FF_DONTCARE,
        _T("楷体")                // 字体名称
    );
    SelectObject(hDC, hFont);

    LPCTSTR lpsz = _T("為 人 民 服 務");
    RECT rct = { 0 };
    GetWindowRect(child_wnd, &rct);
    rct.right -= rct.left, rct.bottom -= rct.top;
    rct.left = 0, rct.top = 0;
    DrawText(hDC, lpsz, lstrlen(lpsz), &rct, DT_SINGLELINE | DT_CENTER | DT_VCENTER);

    DeleteObject(hFont);
    ReleaseDC(child_wnd, hDC);

    Sleep(3000);
    InvalidateRect(child_wnd, nullptr, TRUE);
    UpdateWindow(child_wnd);

    return 0;
}