Clipboard transfer between MACs

Jonathan Morton chromi "at" cyberspace.org
Wed, 27 Jun 2001 13:04:03 +0000


>  >I haven't been able to do a Clipboard transfer between Macs running Mac OS
>>9.x. Is it possible? If so, how?
>
>Ok, well, that's not one I know how to handle. I haven't had easy access to
>an unrestricted MAC in several years now....
>
>What I was referring to is that the VNC protocol already support clipboard
>transfer. I'm surprised if there isn't support in at least one of the MAC
>servers/viewers combinations, but I really don't know. It works with all
>combinations of Xvnc and WinVNC, though.

Unfortunately, that's an unimplemented feature in ChromiVNC for the 
time being.  I can add it to my TO-DO list if it's a 
commonly-requested feature...  Also, I think a number of Mac clients 
don't handle the Clipboard yet either, apart from being able to 
"rapid-type" text from the client Clipboard by sending keypresses 
(this doesn't quite work either, I need to put an anti-overflow 
thingy in the server).

In any case, I'm much more in favour of a dedicated file-transfer 
scheme being added to the RFB protocol, rather than being hacked into 
the Clipboard-transfer stuff.  In particular, the Clipboard on most 
systems has some kind of memory constraint, and may not be 8-bit 
clean for content described as "text".  Do you really want to spend 2 
hours transferring a file only to find there wasn't enough memory to 
hold it all?  Or that the system has munged it, making it useless? 
Or that the server drops the connection as soon as you try, without 
telling you the reason is that it's run out of memory?

Also, the RFB connection would be "locked up" for the duration of the 
transfer, which could be hours for a particularly large file and a 
slow connection.  On top of this, different OSes have differing 
amounts of meta-information associated with a file (some, such as the 
Mac, have entire extra data forks as well as file-type information) 
which it would usually be a good idea to preserve in transit (even if 
it is ignored by the recipient).  Converting filename conventions is 
child's play compared to converting meta-information.

A further "desirable feature" might be to allow multiple files to be 
transferred in a single session, without having to manually select 
new filenames and destinations for each one.  Fair enough, you can 
just as easily make a ZIP or StuffIt or tarball archive and transfer 
that, but what if the required tool isn't on the other end? 
(Different platforms again!)  Such a feature is easily handled by a 
sufficiently well-designed protocol, without excessive code bloat on 
either end of the connection.

If you absolutely have to transfer stuff by the Clipboard, there are 
already tools which let you do that without inserting hacks on top of 
the RFB protocol.  Base64, UUencode, and so on will make an 8-bit 
file ASCII-clean for transfer.  Copy the result into the Clipboard, 
transfer it to the target, and decode it.  For something which 
everyone is supposed to implement, I want something cleaner than 
that, and fully cross-platform compatible.
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from:     Jonathan "Chromatix" Morton
mail:     chromi "at" cyberspace.org  (not for attachments)
website:  http://www.chromatix.uklinux.net/vnc/
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