I just joined the mailing list to tell you about a bug that creates AV's
on Delphi apps. The AV address is in TControl.ScreenToClient. I searched
the mailing list archive as well and I saw that this bug has been
reported earlier.
But I saw nothing about a fix, so I guess it is still an open bug.
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.
This is as far as I've come investigating this, I don't know much about
VNC and what it does to GetProp...but maybe we can solve this together?
// David
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