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Re: Clipboard fetching

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In message <63a3378152.Matthew@sinenomine.freeserve.co.uk>
          Matthew Phillips <spam2011m@yahoo.co.uk> wrote:

> While there are such a large number of clipboard experts in the area....

> For the first time I am implementing clipboard support in an application.  It
> doesn't seem too bad, but one thing I was concerned about is the
> Message_DataRequest where AppNote 240 states that offset 20 should be the
> window handle, and offset 24 an internal handle to indicate the destination.

> I was wondering if bad things would happen if I did not give a window handle.
> Would any clipboard owning task do anything with the window handle value
> other than copy it into the Message_DataSave for the reply?

> Might there be an application out there which used the window handle to
> determine where to send its replying Message_DataSave, rather than using the
> task handle of the task it received the Message_DataRequest from?

Unfortunately, the protocol does not state where the reply should be 
sent to, and since messages can be sent to windows or tasks, the 
recipient could indeed choose to send it to the given window. The 
usual meaning of "replying" to a message is to send the reply to the 
sending task though, so that approach seems unlikely.

Interestingly enough, looking at the EasiWriter source code, there is 
a comment that suggests that some ancient version of EasiWriter 
(before Feb 2000) did probably send the reply to the window/icon 
handles as given at offsets +20 and +24 and not back to the sending 
task. Apparently, at the request of Justin Fletcher EasiWriter was 
changed, so replies to DataRequest messages are sent back to the 
originating task.

> I was wanting to avoid giving a window handle so that the Message_DataSave
> does not get picked up by my event handlers for the ordinary data trabsfer
> protocol.

The message reference can be used to distinguish ordinary save 
requests from other applications from replies to your own DataRequest 
messages. Alternatively, you could have a hidden window just as a 
target for your clipboard requests.

-- 
Martin
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Martin Wuerthner         MW Software      http://www.mw-software.com/
        RISC OS Software for Design, Printing and Publishing
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Thread

Clipboard fetching Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-16 09:04 +0100
  Re: Clipboard fetching Martin Wuerthner <spamtrap@mw-software.com> - 2012-04-19 17:29 +0200
    Re: Clipboard fetching Gerph <gerph@gerph.org> - 2012-04-19 16:18 -0700
      Re: Clipboard fetching Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-20 23:09 +0100
        Re: Clipboard fetching Gerph <gerph@gerph.org> - 2012-04-21 01:18 -0700
          Re: Clipboard fetching Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-21 10:32 +0100
            Re: Clipboard fetching Gerph <gerph@gerph.org> - 2012-04-21 04:26 -0700
              Re: Clipboard fetching Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-22 00:56 +0100
            Re: Clipboard fetching Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-21 16:14 +0200
              Re: Clipboard fetching Matthew Phillips <spam2011m@yahoo.co.uk> - 2012-04-22 00:54 +0100
                Re: Clipboard fetching Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-22 05:37 +0200
                Re: Clipboard fetching Rick Murray <heyrickmail-usenet@yahoo.co.uk> - 2012-04-22 05:42 +0200

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