windows 用于存储对象指针的 GWL_USERDATA 的替代方法是什么？
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What's an alternative to GWL_USERDATA for storing an object pointer?
提问by Benjamin Pollack
In the Windows applications I work on, we have a custom framework that sits directly above Win32 (don't ask). When we create a window, our normal practice is to put thisin the window's user data area via SetWindowLong(hwnd, GWL_USERDATA, this), which allows us to have an MFC-like callback or a tightly integrated WndProc, depending. The problem is that this will not work on Win64, since LONG is only 32-bits wide. What's a better solution to this problem that works on both 32- and 64-bit systems?
在我处理的 Windows 应用程序中，我们有一个直接位于 Win32 之上的自定义框架（不要问）。当我们创建一个窗口时，我们通常的做法是通过 放入this窗口的用户数据区SetWindowLong(hwnd, GWL_USERDATA, this)，这样我们就可以有一个类似 MFC 的回调或一个紧密集成的WndProc，依赖。问题是这在 Win64 上不起作用，因为 LONG 只有 32 位宽。这个问题的更好解决方案是在 32 位和 64 位系统上都有效吗？
回答by Chris
SetWindowLongPtrwas created to replace SetWindowLongin these instances. It's LONG_PTR parameter allows you to store a pointer for 32-bit or 64-bit compilations.
创建SetWindowLongPtr是为了在这些实例中替换SetWindowLong。它的 LONG_PTR 参数允许您存储 32 位或 64 位编译的指针。
LONG_PTR SetWindowLongPtr(
HWND hWnd,
int nIndex,
LONG_PTR dwNewLong
);
Remember that the constants have changed too, so usage now looks like:
请记住，常量也已更改，因此现在的用法如下所示：
SetWindowLongPtr(hWnd, GWLP_USERDATA, this);
Also don't forget that now to retrieve the pointer, you must use GetWindowLongPtr:
另外不要忘记现在要检索指针，您必须使用GetWindowLongPtr：
LONG_PTR GetWindowLongPtr(
HWND hWnd,
int nIndex
);
And usage would look like (again, with changed constants):
用法看起来像（同样，更改了常量）：
LONG_PTR lpUserData = GetWindowLongPtr(hWnd, GWLP_USERDATA);
MyObject* pMyObject = (MyObject*)lpUserData;
回答by Anders
The other alternative is SetProp/RemoveProp (When you are subclassing a window that already uses GWLP_USERDATA)
另一种选择是 SetProp/RemoveProp（当您对已经使用 GWLP_USERDATA 的窗口进行子类化时）
Another good alternative is ATL style thunking of the WNDPROC, for more info on that, see
另一个不错的选择是 WNDPROC 的 ATL 样式 thunking，有关更多信息，请参阅
