Re: Only one instance of a capplet should be allowed

[Paolo Borelli <pborelli katamail com>]

Behdad Esfahbod wrote:
>   3) Those that there's no reason (other than technical reasons)
> to do single-instance.  They typically don't have much shared
> configuration/preferences.  Evince may be a good example of this.
> Evince is single-instance right now, but that's just the way it
> is implemented I guess.  It could have been non-single-instance
> and perform quite the same.
>
>   

There are various reasons, for instnace gedit allows to drag a tab from 
a window to another.
Then there is "document awareness", that is just raise the existing 
window or warn the second time the same file is opened.
Metadata is another reason: both gedit and evince store a file with some 
metadata about files used (current cursor position, last searched word, 
etc) which is much easier to manage with a single instance (no locking).

Obviously startup time and memory consumption are other good reasons, 
though it is still important to make the first instance start fast.


Note however that enforcing a single instance brings its share of 
problems too, that app authors should be aware of: e.g. apps with more 
than a window should never use gtk_dialog_run() since it blocks all the 
windows, not just the one the dialog is modal to.

There are also some UI issues introduced, especially with the 
interaction with workspaces: should a window be moved from a workspace 
to another or should workspaces be handled as indipendent? (no, there 
isn't one true answer :)


Paolo