| EVENT_FUNCS [message #16126] |
Mon, 28 June 1999 00:00  |
philaldis
Messages: 32
Registered: March 1999
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Can anyone possibly describe exactly how event _funcs work.
The reason I am interested is that I would quite like my DERAgrWindow
(direct graphics version of IDLgrWindow), to handle expose events so
that it can protect its colours automatically under an 8 bit display,
if you ask it to.
The problem comes if the user wants to be getting their own events
from the draw widget. I think that I might be able to use event_func
to intercept the ones I want, do something, and then send the events
back up the event train.
Can anyone describe how event_funcs work and what problems there are
with them.
Cheers,
Phil
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| Re: EVENT_FUNCS [message #16153 is a reply to message #16126] |
Fri, 02 July 1999 00:00  |
rmlongfield
Messages: 68
Registered: August 1998
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Member |
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In article <7l9au6$3cf$1@nnrp1.deja.com>,
davidf7203@my-deja.com wrote:
> Phil Aldis writes:
>
>> Can anyone possibly describe exactly how event _funcs work.
>
> Event handler functions work exactly like event handler procedures,
> with this exception: they return a value. If that return value
> is anything else besides a structure that has ID, TOP, and
> HANDLER fields defined as long integers, the return value is ignored
> and the event handler function acts *exactly* like an event handler
> procedure. But if that return value is a structure with those
> fields, the return value is treated as an event structure and it
> is passed up the widget hierarchy just as all events are passed.
Aha, bookmark David's message folks! This is the FIRST time I have seen
written in plain english what the EVENT_FUNC actually returns and how
and where it returns it! David Fanning has used this in the past (I
struggled with a list item widget of his a long time ago with little
success understanding it until now).
Thanks David, and Phil for the asking!
Rose
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