> I made some research about it, and realized that:
>
> The error comes from FindControl (in Controls.pas). Every time you move
> the mouse, the active application - the Delphi app - is notified. In
> order to be able to send mouse move events to the control below (or for
> some other reason), Delphi wants to know which control is under the
> cursor.
>
> Every control/hWnd has a property named "ControlOfs" plus the hInstance
> and the thread ID number. A global atom for this is created at program
> startup.
>
> Therefore, FindControl calls the Win32 function GetProp. And Delphi
> relies on GetProp to return nil/null/0 if the mouse cursor is over
> something else than the application itself. However - this is where
> something goes wrong! When WinVNC is active, GetProp does sometimes
> return something else than nil, which later on makes the Delphi program
> crash.
VNC Uses GlobalAddAtom to add two atoms to the atom table. It does this in
the hook DLL, inside each hooked application. The atoms are used to SetProp
and GetProp on hooked windows. It sounds like Delphi and VNC are somehow
ending up using the same atom values. Do the Delphi apps crash only when a
VNC session is connected, or only when ones _has_ been connected but isn't
any longer, or both?
Can you verify that Delphi creates the atoms correctly with GlobalAddAtom()
and places them in the low-word of the SetProp and GetProp property
paramaters when they're used? (I haven't got Delphi, so I'm afraid I can't
check myself.)
Cheers,
James "Wez" Weatherall
--
"The path to enlightenment is /usr/bin/enlightenment"
Laboratory for Communications Engineering, Cambridge - Tel : 766513
AT&T Labs Cambridge, UK - Tel : 343000
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