Re: [PATCH 0/1] MR9180: win32u: Fix deadlock caused by nested locking.

[Zhao Yi (＠Zhaoyi)]

I reviewed the previous version of the UpdateLayeredWindow function's implementation and noticed that it did not handle the case where the source DC is a window DC separately. Instead, it applied locking uniformly.

```
BOOL X11DRV_UpdateLayeredWindow( HWND hwnd, const UPDATELAYEREDWINDOWINFO *info,
                                 const RECT *window_rect )
{
    struct window_surface *surface;
    struct x11drv_win_data *data;
    BLENDFUNCTION blend = { AC_SRC_OVER, 0, 255, 0 };
    COLORREF color_key = (info->dwFlags & ULW_COLORKEY) ? info->crKey : CLR_INVALID;
    char buffer[FIELD_OFFSET( BITMAPINFO, bmiColors[256] )];
    BITMAPINFO *bmi = (BITMAPINFO *)buffer;
    void *src_bits, *dst_bits;
    RECT rect, src_rect;
    HDC hdc = 0;
    HBITMAP dib;
    BOOL mapped, ret = FALSE;

    if (!(data = get_win_data( hwnd ))) return FALSE;

    data->layered = TRUE;
    if (!data->embedded && argb_visual.visualid) set_window_visual( data, &argb_visual, TRUE );

    rect = *window_rect;
    OffsetRect( &rect, -window_rect->left, -window_rect->top );

    surface = data->surface;
    if (!surface || !EqualRect( &surface->rect, &rect ))
    {
        data->surface = create_surface( data->whole_window, &data->vis, &rect,
                                        color_key, data->use_alpha );
        if (surface) window_surface_release( surface );
        surface = data->surface;

        surface->is_trayicon = is_trayicon(hwnd);
    }
    else set_surface_color_key( surface, color_key );

    if (surface) window_surface_add_ref( surface );
    mapped = data->mapped;
    release_win_data( data );

    /* layered windows are mapped only once their attributes are set */
    if (!mapped)
    {
        DWORD style = NtUserGetWindowLongW( hwnd, GWL_STYLE );

        if ((style & WS_VISIBLE) && ((style & WS_MINIMIZE) || is_window_rect_mapped( window_rect )))
            map_window( hwnd, style, 0 );
    }

    if (!surface) return FALSE;
    if (!info->hdcSrc)
    {
        window_surface_release( surface );
        return TRUE;
    }

    dst_bits = surface->funcs->get_info( surface, bmi );

    if (!(dib = NtGdiCreateDIBSection( info->hdcDst, NULL, 0, bmi, DIB_RGB_COLORS, 0, 0, 0, &src_bits )))
        goto done;
    if (!(hdc = NtGdiCreateCompatibleDC( 0 ))) goto done;

    NtGdiSelectBitmap( hdc, dib );

    surface->funcs->lock( surface );

    if (info->prcDirty)
    {
        intersect_rect( &rect, &rect, info->prcDirty );
        memcpy( src_bits, dst_bits, bmi->bmiHeader.biSizeImage );
        NtGdiPatBlt( hdc, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top, BLACKNESS );
    }
    src_rect = rect;
    if (info->pptSrc) OffsetRect( &src_rect, info->pptSrc->x, info->pptSrc->y );
    NtGdiTransformPoints( info->hdcSrc, (POINT *)&src_rect, (POINT *)&src_rect, 2, NtGdiDPtoLP );

    if (info->dwFlags & ULW_ALPHA) blend = *info->pblend;
    ret = NtGdiAlphaBlend( hdc, rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top,
                           info->hdcSrc, src_rect.left, src_rect.top,
                           src_rect.right - src_rect.left, src_rect.bottom - src_rect.top,
                           *(DWORD *)&blend, 0 );
    if (ret)
    {
        memcpy( dst_bits, src_bits, bmi->bmiHeader.biSizeImage );
        add_bounds_rect( surface->funcs->get_bounds( surface ), &rect );
    }

    surface->funcs->unlock( surface );
    surface->funcs->flush( surface );

done:
    window_surface_release( surface );
    if (hdc) NtGdiDeleteObjectApp( hdc );
    if (dib) NtGdiDeleteObjectApp( dib );
    return ret;
}
```

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/9180#note_119028