C++ 在运行时更改 HWND 窗口过程

Question

我在一个创建 hwnd 及其相应的 WndProc LRESULT CALLBACK 的 IDE 中工作。我需要将 WndProc 更改为自定义的。

我读过 SetWindowLong 可以完成这项工作，但我找不到任何工作示例。例如:

HWND hwnd;//我的窗口

SetWindowLong(hwnd, GWL_WNDPROC, myNewWndProc);

SetWindowLong 的第三个参数是一个 Long，正如函数的名称一样。如何从我的 WndProc 函数引用一个 Long？

我的WndProc:

LRESULT CALLBACK WndProcedure(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam){

msg_dev(toString(uMsg));

switch(uMsg){

    case WM_MOUSEMOVE:
        SetCursor(LoadCursor(NULL, IDC_HAND));
        break;

    case WM_LBUTTONDOWN:
        msg_dev("Button down!");
        break;

    default:
        DefWindowProc(hwnd, uMsg, wParam, lParam);
}

return 0;
};

Answer 1

你需要使用这样的东西:

WNDPROC prevWndProc;
...
prevWndProc = (WNDPROC) SetWindowLongPtr(hwnd, GWL_WNDPROC, (LONG_PTR)&myNewWndProc);
...    
LRESULT CALLBACK myNewWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    msg_dev(toString(uMsg));

    switch(uMsg)
    {
        case WM_MOUSEMOVE:
            SetCursor(LoadCursor(NULL, IDC_HAND));
            break;

        case WM_LBUTTONDOWN:
            msg_dev("Button down!");
            break;
    }

    return CallWindowProc(prevWndProc, hwnd, uMsg, wParam, lParam);
}

查看这篇文章:

When you subclass a window, it's the original window procedure of the window you subclass you have to call when you want to call the original window procedure

也就是说，你应该使用 SetWindowSubclass()而不是 SetWindowLongPtr()。请参阅这篇文章:

Safer subclassing

例如:

SetWindowSubclass(hwnd, &mySubClassProc, 1, 0);
...    
LRESULT CALLBACK mySubClassProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam, UINT_PTR uIdSubclass, DWORD_PTR dwRefData)
{
    msg_dev(toString(uMsg));

    switch(uMsg)
    {
        case WM_MOUSEMOVE:
            SetCursor(LoadCursor(NULL, IDC_HAND));
            break;

        case WM_LBUTTONDOWN:
            msg_dev("Button down!");
            break;

        case WM_NCDESTROY:
            RemoveWindowSubclass(hWnd, &mySubClassProc, 1);
            break;
    }

    return DefSubclassProc(hWnd, uMsg, wParam, lParam);
}