Glenn Wurster wrote:
Our current DIB implementation is an ugly hack. We need a real DIB
implementation, either as a complete GDI engine in Wine or as an X11
extension.
But is it the DIB implementation that is really at fault here or is it
the fact that we are adding extra exceptions and can't be sure what
the esp will be when they fire, especially since they don't occurr on
Windows.
Both are - the current DIB implementation wouldn't work without that
extra exceptions.
The "real" DIB, used for GDI calls, is stored on X side but the DIB
surface, used for direct access, is stored on Wine side and we need to
keep them in sync by catching reads / writes to the DIB surface.
We need to get rid of that seperation - either the DIB should be stored
fully on X side (which would require to add some features to X) or fully
on Wine side (by implementing a GDI renderer in Wine).
And since we already got a full-flegded rendering engine in X11 we
already use (and will continue to use unless we wanna drop network
transparency) I think the right way would be to add the missing features
to X (which would just be XPixmaps of arbitrary depth as we should be
able to use SHM for direct memory access).
As far as I can tell, the problem is that we have extra exceptions
firing when the application is not expecting them and they would not
occurr on Windows. So, the two options are to enforce that Wine never
throws exceptions other than those that occurr on windows (and I
suspect people in general do not like this restriction for performance
reasons) or to fix the exception handler to work in the face of a bad
ESP. Perhaps exceptions fired due to wine can use a different stack
so that they don't rely on an assumed state of the application?
I dunno if that's possible but it would be yet another hack to
workaround limitations of the current DIB hack (which also has other
limitations that just *can't* be worked around).
Some work has been done on a GDI engine in Wine by Transgaming a couple
of years ago but it wasn't merged. Then, some weeks ago someone
suggested to port the ReactOS GDI engine to Wine.
Yes, I read that. The Transgaming engine that was discussed uses
exceptions to detect when the application modifies a DIB, which is the
problem we have right now.
Does it? I see no reason for that...
I don't know how the ReactOS GDI engine does it.
I'm just talking about the render engine - a "real" GDI implementation
doesn't need those exceptions (as you can observe on Windows).
Felix
