我正在学习WinAPI。 MSDN:
WS_EX_CONTEXTHELP
窗口的标题栏包含一个问题 标记。当用户单击问号时,光标变为a 带指针的问号。如果用户然后单击子窗口, 孩子收到WM_HELP消息。子窗口应该通过 消息到父窗口过程,应该调用WinHelp 函数使用HELP_WM_HELP命令。帮助应用程序显示 一个弹出窗口,通常包含子窗口的帮助。
WS_EX_CONTEXTHELP不能与WS_MAXIMIZEBOX一起使用 WS_MINIMIZEBOX样式。
当我尝试在代码中使用WS_EX_CONTEXTHELP
时,我看不到问号。我没有在代码中指出WS_MAXIMIZEBOX
或WS_MINIMIZEBOX
值:
为什么会这样?我的“Hello World”代码:
#include <Windows.h>
#include <tchar.h>
#include <iostream>
#include <exception>
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 0 :(得分:3)
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_OVERLAPPEDWINDOW
和WS_MAXIMIZEBOX
的窗口样式WS_MINIMIZEBOX
。