WNDCLASSEX Structure

The WNDCLASSEX structure contains information about a window class. It is used with the RegisterClassEx function to register a window class for subsequent use in creating windows.

Definition

typedef struct _WNDCLASSEX {
    UINT      cbSize;
    UINT      style;
    WNDPROC   lpfnWndProc;
    int       cbClsExtra;
    int       cbWndExtra;
    HINSTANCE hInstance;
    HICON     hIcon;
    HCURSOR   hCursor;
    HBRUSH    hbrBackground;
    LPCSTR    lpszMenuName;
    LPCSTR    lpszClassName;
    HICON     hIconSm;
} WNDCLASSEX, *PWNDCLASSEX;

Members

Member	Type	Description
`cbSize`	UINT	Size of this structure, in bytes. Must be set to `sizeof(WNDCLASSEX)`.
`style`	UINT	Class style(s) (e.g., `CS_VREDRAW`, `CS_HREDRAW`).
`lpfnWndProc`	WNDPROC	Pointer to the window procedure for this class.
`cbClsExtra`	int	Number of extra bytes to allocate following the class structure.
`cbWndExtra`	int	Number of extra bytes to allocate following the window instance.
`hInstance`	HINSTANCE	Handle to the instance that contains the window procedure.
`hIcon`	HICON	Handle to the class icon.
`hCursor`	HCURSOR	Handle to the class cursor.
`hbrBackground`	HBRUSH	Handle to the class background brush.
`lpszMenuName`	LPCSTR	Resource name of the class menu, or `NULL`.
`lpszClassName`	LPCSTR	String or atom that uniquely identifies the window class.
`hIconSm`	HICON	Handle to a small icon associated with the class.

C++ Example

#include <windows.h>

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
}

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, LPSTR lpCmdLine, int nShowCmd) {
    WNDCLASSEX wc = {0};
    wc.cbSize        = sizeof(WNDCLASSEX);
    wc.style         = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc   = WndProc;
    wc.cbClsExtra    = 0;
    wc.cbWndExtra    = 0;
    wc.hInstance     = hInst;
    wc.hIcon         = LoadIcon(nullptr, IDI_APPLICATION);
    wc.hCursor       = LoadCursor(nullptr, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszMenuName  = nullptr;
    wc.lpszClassName = "MyWindowClass";
    wc.hIconSm       = LoadIcon(nullptr, IDI_APPLICATION);

    if (!RegisterClassEx(&wc)) {
        MessageBox(nullptr, "Window Registration Failed!", "Error", MB_ICONERROR);
        return 0;
    }

    HWND hwnd = CreateWindowEx(
        0,
        wc.lpszClassName,
        "Sample Window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 640, 480,
        nullptr, nullptr, hInst, nullptr);

    if (!hwnd) {
        MessageBox(nullptr, "Window Creation Failed!", "Error", MB_ICONERROR);
        return 0;
    }

    ShowWindow(hwnd, nShowCmd);
    UpdateWindow(hwnd);

    MSG msg;
    while (GetMessage(&msg, nullptr, 0, 0) > 0) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return (int)msg.wParam;
}

For more details, see the related pages: