[Qt-interest] native HWND in QWidget::create opens separate window

[Christopher Lux]

Hi,
i need to use a native window for some special rendering task (on
Windows and Linux). Now on Windows, after i create the Window i call
QWidget::create() using the just created HWND. It seems to work very
well, i can receive events from this window in Qt and so on. But
instead of being embedded instead of the original widget i now have a
second window open.

I want the created window to replace the widget and not open up as a
new window. Is there anything i can do to achieve this?

Here the code snippet to open the window:

wnd_style    = WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN | WS_CLIPSIBLINGS;
wnd_style_ex = 0;

math::vec2i wnd_position = in_display->_impl->_info->_screen_origin +
in_position;
RECT        wnd_rect;

::SetRect(&wnd_rect, 0, 0, in_size.x, in_size.y);

if (0 == ::AdjustWindowRectEx(&wnd_rect, wnd_style, false, wnd_style_ex)) {
    ...
}

_window_handle = ::CreateWindowEx(wnd_style_ex,
reinterpret_cast<LPCSTR>(in_display->_impl->_window_class),
                                  in_title.c_str(),
                                  wnd_style,
                                  wnd_position.x, wnd_position.y,
                                  wnd_rect.right - wnd_rect.left,
wnd_rect.bottom - wnd_rect.top,
                                  0, 0, in_display->_impl->_hinstance,
                                  0);

Now here is the initialization code of the custom Widget:


viewer_widget::viewer_widget(QWidget* parent, // parent is not 0!
                             const wm::context::attribute_desc&   ctx_attrib,
                             const wm::surface::format_desc&      win_fmt)
  : QWidget(parent, Qt::MSWindowsOwnDC)
{
    setMouseTracking(true);
    setFocusPolicy(Qt::StrongFocus);

    setAttribute(Qt::WA_NativeWindow, true);
    setAttribute(Qt::WA_PaintOnScreen, true); // disables qt double
buffering (seems X11 only since qt4.5, ...)
    //setAttribute(Qt::WA_OpaquePaintEvent, true);
    setAttribute(Qt::WA_NoSystemBackground, true);
    //setAttribute(Qt::WA_ForceUpdatesDisabled, true);
    //setAttribute(Qt::WA_PaintUnclipped, true);
    setAutoFillBackground(false);

    ... after creating the window....

    this->create(_window_handle, true, true);
}

Now the window works as expected but comes up as a separate window
instead of replacing the widgets window.

Regards
-chris