我怎样才能使WinProc可以访问用它创建的对象? [英] How can I have WinProc have access to objects created out of it?

问题描述

在某个时候，我有这个

LRESULT CALLBACK WinProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    if(msg==WM_CREATE)
    {
        LPCREATESTRUCT pcs = (LPCREATESTRUCT)lParam;
            D2DResources* pD2DResources = (D2DResources*)pcs->lpCreateParams;

            ::SetWindowLongPtrW(
                hWnd,
                GWLP_USERDATA,
                PtrToUlong(pD2DResources)
                );
    }
    else
    {
        D2DResources* pD2DResources = reinterpret_cast<D2DResources*>(static_cast<LONG_PTR>(
            ::GetWindowLongPtrW(
                hWnd,
                GWLP_USERDATA
                )));

        switch(msg)
        {

    case WM_PAINT:
        {
            pD2DResources->OnRender();
            ValidateRect(hWnd, NULL);
        }
        break;

    case WM_SIZE:
        {
            UINT width = LOWORD(lParam);
            UINT height = HIWORD(lParam);
            pD2DResources->OnResize(width, height);
        }
        break;

因此，我的WinProc可以访问以前创建的D2DResources.现在，我希望它可以访问另一个先前创建的对象.我怎么做?我的意思是，它可以访问多个以前创建的对象吗?如果可以，怎么办?

So my WinProc has access to a previously created D2DResources. Now I want it to have access to another previously created object. How do I do that? I mean, can it have access to more than one previously created object? If so, how?

Raymond Chen说:将指针作为lpCreateParams传递到结构.您可以在结构中放入任何所需的内容.我怎么做?有人可以给我一个例子吗?

Raymond Chen said: "Pass a pointer to a structure as the lpCreateParams. You can put anything you want in the structure." How do I do that? Can anyone give me an exemple?

推荐答案

创建您自己的结构，并在创建它时将其传递给窗口.您可以在其中放置任何您喜欢的东西，包括指向其他​​东西的指针.

Create your own structure and pass it to the window when you create it. You can put anything you like in there, including pointers to other things.

例如

struct MyWindowData
{
    D2DResources*   pD2DResources;
    void*       pMyOtherData;
    int     iSomethingElse;
};


// on window creation
MyWindowData* pData = new MyWindowData(...);
HWND hWnd = CreateWindowEx(..., pData); // window will own the data and destroy it itself

// in the window procedure
if (msg == WM_CREATE)
{
    MyWindowData* pData = ((LPCREATESTRUCT)lParam)->lpCreateParams;
    SetWindowLongPtr(hWnd, GWLP_USERDATA, (ULONG_PTR)pData);
}
else
{
    MyWindowData* pData = (MyWindowData*)GetWindowLongPtr(hWnd, GWLP_USERDATA);
    switch (msg)
    {
        case WM_PAINT:
            pData->pD2DResources->OnRender();
            break;

        case WM_NCDESTROY:
            delete pData; // delete data on destroy
            break;
    }

    ...
}

这篇关于我怎样才能使WinProc可以访问用它创建的对象?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！