Instance Subclassing Demo

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#include <windows.h>

#define BUTTON1 1

WNDPROC OldWndProc;
HWND hwndbtn;

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK SubClassProc(HWND, UINT, WPARAM, LPARAM);


int WINAPI WinMain(
HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{

    WNDCLASSEX wc;
    MSG msg;


    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = 0;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = TEXT("myWindowClass");
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);


    RegisterClassEx(&wc);


    CreateWindowEx(
        WS_EX_CLIENTEDGE,
        TEXT("myWindowClass"),
        TEXT("Instance Subclassing"),
        WS_VISIBLE | WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT,
        CW_USEDEFAULT,
        240,
        180,
        NULL,
        NULL,
        hInstance,
        NULL);


    while(GetMessage(&msg,NULL,0,0)>0)
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }


    return msg.wParam;
}



LRESULT CALLBACK WndProc(
HWND hwnd,
UINT msg,
WPARAM wParam,
LPARAM lParam)
{

    switch(msg)
    {

    case WM_CREATE:
    {

        hwndbtn = CreateWindow(
            TEXT("BUTTON"),
            TEXT("Button 1"),
            WS_CHILD |
            WS_VISIBLE |
            BS_CENTER,
            10,
            10,
            100,
            80,
            hwnd,
            (HMENU)BUTTON1,
            GetModuleHandle(NULL),
            NULL);


        // Replace the button window procedure
        OldWndProc =
        (WNDPROC)SetWindowLong(
            hwndbtn,
            GWL_WNDPROC,
            (LONG)SubClassProc);


        break;
    }


    case WM_DESTROY:

        // restore original procedure
        SetWindowLong(
            hwndbtn,
            GWL_WNDPROC,
            (LONG)OldWndProc);


        PostQuitMessage(0);
        break;

    }


    return DefWindowProc(hwnd,msg,wParam,lParam);
}




// New button procedure
LRESULT CALLBACK SubClassProc(
HWND hwnd,
UINT uMsg,
WPARAM wParam,
LPARAM lParam)
{

    switch(uMsg)
    {

    case WM_LBUTTONDOWN:

        MessageBeep(MB_ICONEXCLAMATION);

        break;


    case WM_RBUTTONDOWN:

        MessageBox(
            hwnd,
            TEXT("Right mouse button pressed"),
            TEXT("Subclass"),
            MB_OK);

        break;

    }


    // pass message back to original button procedure
    return CallWindowProc(
        OldWndProc,
        hwnd,
        uMsg,
        wParam,
        lParam);
}