nanogui: Why does microwindow (API Win32) display child window first ?
Subject:
Re: [nanogui] Why does microwindow (API Win32) display child window first ?
From:
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Date:
1 May 2002 21:20:54 -0000
Message-Id: <1020287539.3cd05a339b7a6@imp.free.fr>
> > I presently work on transparency in microwindow through the Win32
> API.
> > I do not understand the redrawing strategy of microwindow.
> > When redrawing a window, Microwindow redraw children windows BEFORE
> mother
> > window.
>
> I think that Windows uses the same strategy, so that child
> windows appear before the background windows. Due
> to other considerations, we still have to use the clipping
> mechanism, since the child windows need to be contained
> in their parent.
>
>
No, it is not right Window redraw mother BEFORE children. I have done some
tests under Win2000 and the redrawing strategy is systematically mother BEFORE
child. Furthermore if i ask a mother redrawing, it automatically send WM_PAINT
to the children.
>
>
> > - With the current strategy, we are not able to manage transparency
> quite
> > being 100% compliant with the Win32 API.
>
> I'd like to hear more about this.
>
Under window, it is easy to manage transparency, because when a window receive
the WM_PAINT it can assume that the complete under window had already been
redraw.
Under MicroWindow the repaint order is not predictable, it depend on the
chained list order. So when a window receive the WM_PAINT it can't assume that
the under window had already been redraw. In fact, cause of the clipping we
allways get a black area. With that strategy we can't manage transparency in
the same way has Window.
I work on modifications to be Window compliant, it need 2 kinds :
1st - we must not clip children sytematically, WS_CLIPCHILD and WS_CLIPSIBLING
must be avoid in CreateWindowEx. But i don't fell all the sides effect of it.
2nd - i think of a solution to redraw window from mother to children, not
following the chaine list of the window, but following the tree built by
mother, children and sibling window.
I face some problems, because the WM_PAINT message is not manage in the same
way than other messages.
I will send a patch of my modifications as soon as possible.
Thanks for all
TSI Alpha3i's Team
Damien
