为什么我在使用WS_EX_CONTEXTHELP时看不到问号？
我正在学习WinAPI。 MSDN ：
WS_EX_CONTEXTHELP
窗口的标题栏包含问号。 当用户单击问号时，光标将变为带有指针的问号。 如果用户然后单击子窗口，则子项将收到WM_HELP消息。 子窗口应该将消息传递给父窗口过程，该过程应该使用HELP_WM_HELP命令调用WinHelp函数。 “帮助”应用程序显示一个弹出窗口，该窗口通常包含子窗口的帮助。
WS_EX_CONTEXTHELP不能与WS_MAXIMIZEBOX或WS_MINIMIZEBOX样式一起使用。
当我尝试在我的代码中使用WS_EX_CONTEXTHELP ，我没有看到问号。 我没有在我的代码中指出WS_MAXIMIZEBOX或WS_MINIMIZEBOX值：
为什么会这样？ 我的“Hello World”代码：
#include #include #include #include using namespace std; #define APP_RC_SUCCEEDED 0 #define APP_RC_UNHANDLED_EXCEPTION 1 #define APP_RC_UNKNOWN_ERROR 2 #define APP_RC_WINDOW_CLASS_WAS_NOT_REGISTERED 3 #ifdef UNICODE #define TCOUT std::wcout #define TCIN std::wcin #define TCERR std::wcerr #else #define TCOUT std::cout #define TCIN std::cin #define TCERR std::cerr #endif LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpszCmdLine, INT iShow) try { LPCTSTR className = _T("{AAAEB8BF-04C5-4DEA-96C1-FC14F7E66A35}"); WNDCLASSEX wndclassex; ZeroMemory(&wndclassex, sizeof(wndclassex)); wndclassex.cbSize = sizeof(wndclassex); wndclassex.lpszClassName = className; wndclassex.cbClsExtra = 0; wndclassex.cbWndExtra = 0; wndclassex.hInstance = hInstance; wndclassex.lpfnWndProc = WndProc; wndclassex.hIcon = LoadIcon(NULL, IDI_APPLICATION); wndclassex.hIconSm = LoadIcon(NULL, IDI_APPLICATION); wndclassex.hCursor = LoadCursor(NULL, IDC_ARROW); wndclassex.lpszMenuName = NULL; wndclassex.style = CS_HREDRAW | CS_VREDRAW; wndclassex.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH); ATOM wAtom = RegisterClassEx(&wndclassex); if (!wAtom) { DWORD errCode = GetLastError(); TCERR << _T("Function: RegisterClassEx. System Error Code: ") << errCode << endl; return APP_RC_WINDOW_CLASS_WAS_NOT_REGISTERED; } HWND hwnd = CreateWindowEx( WS_EX_CONTEXTHELP, className, _T("This is the title text..."), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL); ShowWindow(hwnd, iShow); UpdateWindow(hwnd); MSG msg; while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return APP_RC_SUCCEEDED; } catch (exception ex) { TCERR << ex.what() << endl; return APP_RC_UNHANDLED_EXCEPTION; } catch (...) { TCERR << _T("Unknown error.") << endl; return APP_RC_UNKNOWN_ERROR; } LRESULT CALLBACK WndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { HDC hdc; PAINTSTRUCT ps; RECT rect; switch (uMsg) { case WM_CREATE: return 0; case WM_PAINT: hdc = BeginPaint(hwnd, &ps); GetClientRect(hwnd, &rect); DrawText(hdc, _T("Hello!"), -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER); EndPaint(hwnd, &ps); return 0; case WM_DESTROY: PostQuitMessage(APP_RC_SUCCEEDED); return 0; default: return DefWindowProc(hwnd, uMsg, wParam, lParam); } }
答案可以在您的问题中包含的文档引用中找到：
WS_EX_CONTEXTHELP不能与WS_MAXIMIZEBOX或WS_MINIMIZEBOX样式一起使用。
您指定了包含WS_MAXIMIZEBOX和WS_MINIMIZEBOX的窗口样式WS_OVERLAPPEDWINDOW 。