Carl
Have you been down the TAction route?
Also I have a TControlLink Component I wrote which uses RTTI to
'hook' events and on this event update a dataset parameter from a publish
property
(source as always is free on request)
Regards
Neven
----- Original Message -----
From: Carl Reynolds <[EMAIL PROTECTED]>
To: Multiple recipients of list delphi <[EMAIL PROTECTED]>
Sent: Wednesday, 28 June 2000 17:38
Subject: [DUG]: Chaining events and WindowProc
> Suppose I have a control on my form that I want to link a certain
component
> to that will intercept some of the messages to the control and make it
> behave differently; eg. suppose I want to intercept the control's
OnKeyPress
> event and perform an action based on it. Assume that this control could
> actually be any TWinControl descendant, not something I've specifically
> created myself.
>
> The only way I can think of to do this is either to reassign the control's
> OnKeyPress event or its WindowProc to one controlled by the new component.
> But this is a logistical nightmare either way! Take WindowProc for
example:
>
> If my component assigns the control's WindowProc to one of its own
> procedures on creation and assigns it to the old value on destruction (eg.
a
> TDockTree does this), then that is fine as long as no other component has
> done the same thing. But if I have two components (for example) and, in
> order, create component one, create component two, free one, and free two,
> the WindowProc for the control will end up pointing to that of component
one
> - which has already been free'd!!
>
> I could implement a stack to hold WindowProc changes for the control, and
> use methods on this stack to keep things in order. But everything will be
> broken if any third party component does the same thing, eg. if the
control
> were a docksite, because TDockTree will reassign its WindowProc at the
point
> it is created.
>
> Reassigning the OnKeyPress event would encounter similar problems. Is
there
> any way around this?
>
> Cheers,
> Carl
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