[scribus] Multiple instances of Scribus

[Craig Ringer]

William F. Maddock wrote:
> On Mon, 2008-04-28 at 11:01 -0400, Gregory Pittman wrote:
>   
>> Well, yes this is a Linux feature. Prior to Linux, the standard desktop 
>> computer behavior was to not allow one to start up a program already 
>> running. If Windows or Macs or whatever behave this way now, it's an 
>> adoption of this Linux behavior, not something they invented.
>>     
>
> Actually, Amiga was doing this before Linux ever showed up on the scene,
> and Amiga got it from Unix. Mac probably got it from Unix as well. Can't
> say about Windows

Furthermore, Windows applications are free to appear to open a file many 
times too. The only restriction in Windows is against opening a file 
while there's an existing file handle (and even that's actually a rather 
weak limitation - it depends on which API calls you use, what mode the 
existing file handle was opened with, etc). As many programs read a file 
into RAM they can and often do just close the file handle.

Scribus could just keep a file handle open for the file after reading it 
in, and release it when the document is closed. That'll prevent another 
instance from opening it again, and it can use other internal checks to 
detect whether the same instance is reopening the file. However, that'll 
only work for Windows and keeps a file handle open needlessly; I'd 
instead want to see if Windows has any sort of advisory locking.

On Unix/Linux the best choice is advisory locking with fadvise() and 
friends.

On Mac OS X it depends on the APIs you use. With the Carbon file APIs 
you get Windows-like automatic mandatory locking. With the POSIX/BSD 
calls you get UNIX-like behaviour. Again, though, advisory locking is 
probably better.

That's a lot of platform specific messing around, though, for a pretty 
trivial feature. Personally I wouldn't bother.

--
Craig Ringer