Question

So I’m trying to get into some directX programming so I’m following this book called “Beginning DirectX 11 Game Programming”, but I’m stuck already at the second example.

I’ve spend roughly an hour searching for a solution to this problem, but havn’t been able to find anything that could help me.

So the error code I’m getting is this.:

Main.obj : error LNK2019: unresolved external symbol "long __stdcall WndProc(struct HWND__ *,unsigned int,unsigned int,long)" (?WndProc@@YGJPAUHWND__@@IIJ@Z) referenced in function _wWinMain@16

And here’s the code – written exactly as in the book, except for LRESULT CALLBACK WndProc

#include <Windows.h>

LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam );

int WINAPI wWinMain( HINSTANCE hInstance, HINSTANCE prevInstance, LPWSTR cmdLine, int cmdShow )
{
    UNREFERENCED_PARAMETER( prevInstance );
    UNREFERENCED_PARAMETER( cmdLine );

    WNDCLASSEX wndClass = { 0 };
    wndClass.cbSize = sizeof( WNDCLASSEX );
    wndClass.style = CS_HREDRAW | CS_VREDRAW;
    wndClass.lpfnWndProc = WndProc;
    wndClass.hInstance = hInstance;
    wndClass.hCursor = LoadCursor( NULL, IDC_ARROW );
    wndClass.hbrBackground = ( HBRUSH )( COLOR_WINDOW + 1 );
    wndClass.lpszMenuName = NULL;
    wndClass.lpszClassName = "DX11BookWindowClass";

    if( !RegisterClassEx( &wndClass ) )
        return -1;

    RECT rc = { 0,0,640,480 };
    AdjustWindowRect( &rc, WS_OVERLAPPEDWINDOW, FALSE );

    HWND hwnd = CreateWindowA( "DX11BookWindowClass", "Blank Win32 Window", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, rc.right - rc.left,
                                rc.bottom - rc.top, NULL, NULL, hInstance, NULL );

    if( !hwnd )
        return -1;

    ShowWindow( hwnd, cmdShow );

    return 0;
}

Answer 1

Returning 0 from your WndProc callback IS a terrible idea if you’re not handling any messages. So you can either define it to handle messages yourself, or simply use the default procedure:

wndClass.lpfnWndProc = DefWindowProc;

Alternatively:

LRESULT CALLBACK WndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam ) { return DefWindowProc(hWnd, msg, wParam, lParam); }

Which you should do whenever you don’t handle your messages.