Win32 C++ 实现对话框居中显示

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使用 MessageBox 对话框显示信息时, 对话框位置总是在屏幕中间, 而不是主窗口的中间, 如何以最简单的方式将对话框移到父窗口中间呢? 那就是使用 CBT 钩子 , 在窗口创建完成前(窗口句柄已经创建完成), 修改窗口的位置, 即可实现对话框在父窗口上居中显示.

首先简单写一个 CBT 钩子类, 这个类暂且叫做 CMessageBoxCenter

MessageBoxCenter.h

#pragma once
#include <windows.h>class CMessageBoxCenter
{public:CMessageBoxCenter();~CMessageBoxCenter();// 获取子窗口位于父窗口的居中位置static POINT GetChildWindowCenterPos(int nWidth,         //子窗口宽度int nHeight,        //子窗口高度HWND hParent        //父窗口句柄);private:// WH_CBT // 线程或全局// https://learn.microsoft.com/zh-cn/windows/win32/winmsg/cbtproc// 安装用于接收对 CBT 应用程序有用的通知的挂钩过程static LRESULT CALLBACK CBTProc(int nCode, WPARAM wParam, LPARAM lParam);private:static HHOOK m_hHook;
};

MessageBoxCenter.cpp

#include "MessageBoxCenter.h"HHOOK CMessageBoxCenter::m_hHook;CMessageBoxCenter::CMessageBoxCenter()
{m_hHook = ::SetWindowsHookEx(WH_CBT, CBTProc, NULL, ::GetCurrentThreadId());
}CMessageBoxCenter::~CMessageBoxCenter()
{::UnhookWindowsHookEx(m_hHook);
}POINT CMessageBoxCenter::GetChildWindowCenterPos(int nWidth,         //子窗口宽度int nHeight,        //子窗口高度HWND hParent        //父窗口句柄
)
{RECT rectParent = { 0 };LONG nParentW = 0;LONG nParentH = 0;// 如果父窗口句柄为空, 则以桌面窗口为父窗口if (NULL == hParent){hParent = ::GetDesktopWindow();}// 获取并统计父窗口宽度和高度::GetWindowRect(hParent, &rectParent);nParentW = rectParent.right - rectParent.left;nParentH = rectParent.bottom - rectParent.top;return {rectParent.left + (nParentW - nWidth) / 2, rectParent.top + (nParentH - nHeight) / 2};
}LRESULT CALLBACK CMessageBoxCenter::CBTProc(int nCode, WPARAM wParam, LPARAM lParam)
{// 即将创建一个窗口if (HCBT_CREATEWND == nCode){HWND hWndNew = (HWND)wParam;LPCBT_CREATEWND pStruct = (LPCBT_CREATEWND)lParam;HWND hParent = pStruct->lpcs->hwndParent;// 检查是对话框, 则修改显示位置为相对父窗口居中位置if (32770 == ::GetClassLongPtr(hWndNew, GCW_ATOM)){POINT nPos = GetChildWindowCenterPos(pStruct->lpcs->cx, pStruct->lpcs->cy, hParent);pStruct->lpcs->x = nPos.x;pStruct->lpcs->y = nPos.y;}}return ::CallNextHookEx(m_hHook, nCode, wParam, lParam);
}

以下测试例子简单写了个对话框过程, 仅简单测试对话框

main.cpp

#include <windows.h>
#include <tchar.h>
#include <locale.h>
#include"resource.h"
#include "MessageBoxCenter.h"#pragma comment(linker,"\"/manifestdependency:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'\"")INT_PTR WINAPI DialogProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);int WINAPI WinMain(_In_ HINSTANCE hInstance,_In_opt_ HINSTANCE hPrevInstance,_In_ LPSTR lpCmdLine,_In_ int nShowCmd)
{setlocale(LC_ALL, "");UNREFERENCED_PARAMETER(hInstance);UNREFERENCED_PARAMETER(hPrevInstance);UNREFERENCED_PARAMETER(lpCmdLine);UNREFERENCED_PARAMETER(nShowCmd);WORD wID = ::DialogBoxParam(GetModuleHandle(NULL),  MAKEINTRESOURCE(IDD_DIALOG_FRAME), nullptr, DialogProc, (LPARAM)0);return wID;
}INT_PTR WINAPI DialogProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{if (WM_INITDIALOG == uMsg){return (INT_PTR)TRUE;}if (WM_CLOSE == uMsg){::EndDialog(hWnd, 0);return (INT_PTR)TRUE;}if (WM_COMMAND == uMsg){//消息源   HIWORD(wParam)      LOWORD(wParam)     lParam //菜单     0                   菜单ID             0//快捷键   1                   快捷键ID           0//控件     控件定义的通知码    控件ID             控件窗口句柄WORD wNotify = HIWORD(wParam);WORD wID = LOWORD(wParam);HWND hWndCtrl = (HWND)lParam;if (wID >= IDOK && wID <= IDNO){::EndDialog(hWnd, wID);}if (IDC_BUTTON_CBT == wID){CMessageBoxCenter boxCenter;MessageBox(hWnd, _T("WH_CBT 钩子测试, 居中显示对话框"), _T("WH_CBT 钩子"), MB_OK);}return (INT_PTR)TRUE;}return (INT_PTR)FALSE;
}

resource.h

//{{NO_DEPENDENCIES}}
// Microsoft Visual C++ 生成的包含文件。
// 供 Win32Hook.rc 使用
//
#define IDD_DIALOG_FRAME                101
#define IDC_BUTTON_CBT                  1001// Next default values for new objects
// 
#ifdef APSTUDIO_INVOKED
#ifndef APSTUDIO_READONLY_SYMBOLS
#define _APS_NEXT_RESOURCE_VALUE        103
#define _APS_NEXT_COMMAND_VALUE         40001
#define _APS_NEXT_CONTROL_VALUE         1002
#define _APS_NEXT_SYMED_VALUE           101
#endif
#endif

Win32Hook.rc

// Microsoft Visual C++ generated resource script.
//
#include "resource.h"#define APSTUDIO_READONLY_SYMBOLS
/
//
// Generated from the TEXTINCLUDE 2 resource.
//
#include "winres.h"/
#undef APSTUDIO_READONLY_SYMBOLS/
// 中文(简体，中国) resources#if !defined(AFX_RESOURCE_DLL) || defined(AFX_TARG_CHS)
LANGUAGE LANG_CHINESE, SUBLANG_CHINESE_SIMPLIFIED#ifdef APSTUDIO_INVOKED
/
//
// TEXTINCLUDE
//1 TEXTINCLUDE 
BEGIN"resource.h\0"
END2 TEXTINCLUDE 
BEGIN"#include ""winres.h""\r\n""\0"
END3 TEXTINCLUDE 
BEGIN"\r\n""\0"
END#endif    // APSTUDIO_INVOKED/
//
// Dialog
//IDD_DIALOG_FRAME DIALOGEX 0, 0, 309, 176
STYLE DS_SETFONT | DS_MODALFRAME | DS_FIXEDSYS | DS_CENTER | WS_POPUP | WS_CAPTION | WS_SYSMENU
CAPTION "WinHook"
FONT 8, "MS Shell Dlg", 400, 0, 0x1
BEGINDEFPUSHBUTTON   "确定",IDOK,73,142,50,14PUSHBUTTON      "取消",IDCANCEL,181,141,50,14PUSHBUTTON      "WH_CBT 居中显示对话框",IDC_BUTTON_CBT,19,18,91,14
END/
//
// DESIGNINFO
//#ifdef APSTUDIO_INVOKED
GUIDELINES DESIGNINFO
BEGINIDD_DIALOG_FRAME, DIALOGBEGINLEFTMARGIN, 7RIGHTMARGIN, 302TOPMARGIN, 7BOTTOMMARGIN, 169END
END
#endif    // APSTUDIO_INVOKED/
//
// AFX_DIALOG_LAYOUT
//IDD_DIALOG_FRAME AFX_DIALOG_LAYOUT
BEGIN0
END#endif    // 中文(简体，中国) resources
/#ifndef APSTUDIO_INVOKED
/
//
// Generated from the TEXTINCLUDE 3 resource.
///
#endif    // not APSTUDIO_INVOKED

对话框效果