用于存储对象指针的 GWL_USERDATA 的替代方法是什么? [英] What's an alternative to GWL_USERDATA for storing an object pointer?
问题描述
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SetWindowLong(hwnd, GWL_USERDATA, this)
把this
放到窗口的用户数据区中,这样我们就可以有一个MFC- 类似回调或紧密集成的 WndProc
,视情况而定.问题是这在 64 位 Windows 上不起作用,因为 LONG 只有 32 位宽.对于这个问题,有什么更好的解决方案既适用于 32 位系统,也适用于 64 位系统?
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 this
in 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 64-bit Windows, since LONG is only 32-bits wide. What's a better solution to this problem that works on both 32- and 64-bit systems?
推荐答案
SetWindowLongPtr 的创建是为了替换 在这些情况下,SetWindowLong.它的 LONG_PTR 参数允许您为 32 位或 64 位编译存储一个指针.
SetWindowLongPtr was created to replace SetWindowLong in these instances. It's LONG_PTR parameter allows you to store a pointer for 32-bit or 64-bit compilations.
LONG_PTR SetWindowLongPtr(
HWND hWnd,
int nIndex,
LONG_PTR dwNewLong
);
请记住,常量也发生了变化,所以现在的用法如下:
Remember that the constants have changed too, so usage now looks like:
SetWindowLongPtr(hWnd, GWLP_USERDATA, this);
另外不要忘记现在要检索指针,您必须使用 GetWindowLongPtr:
Also don't forget that now to retrieve the pointer, you must use GetWindowLongPtr:
LONG_PTR GetWindowLongPtr(
HWND hWnd,
int nIndex
);
并且用法看起来像(同样,更改了常量):
And usage would look like (again, with changed constants):
LONG_PTR lpUserData = GetWindowLongPtr(hWnd, GWLP_USERDATA);
MyObject* pMyObject = (MyObject*)lpUserData;
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