[Sugar-devel] One instance activity
bert at freudenbergs.de
Wed Dec 10 04:28:07 EST 2008
On 10.12.2008, at 03:57, david at lang.hm wrote:
> On Tue, 9 Dec 2008, Bert Freudenberg wrote:
>> On 09.12.2008, at 18:55, Eben Eliason wrote:
>>> Are you sure? Browse makes use of shared code, but still presents
>>> user with the appearance of multiple instances.
>> The way to do it would be to create a unique D-Bus service in your
>> activity. When the second instance tries to create that service it
>> will notice that it already exists. It could then notify its first
>> instance via said D-Bus service.
> you don't need to use D-Bus for this, it can be done by X without
> any other communication channels.
> I don't know the details for how to do this, but I've seen mozilla/
> firefox do this for a few years. to see this start firefox on one
> machine, connect to another machine and point the display back to
> the first one. then try and start firefox on that second machine.
> the end result will be a new window opening up, but running on the
> first machine (if you have trouble seeing the difference, make the
> two machines have different bookmarks, or give one network access
> that the other doesn't have)
> please don't develop new mechanisms to do things that already exist.
It's not a new mechanism. The usage of a named D-Bus service to ensure
unique program instances is documented and not my invention (though I
cannot remember where I saw it first).
I should have written "One way to do this would be ...", I give you
But you cannot know which way would be preferable for a given
activity. And since it is private to the activity and does not affect
other activities, no harm is done either way.
E.g., twiddling X properties is hard in various high-level languages,
in particular when using higher-level UI toolkits. Sugar currently
requires two custom X properties and this is causing activity authors
considerable pain. Even Sugar itself had to resort to C code, adding a
custom native library to manipulate these properties, it was not easy
in pure Python. This is in stark contrast to the nicely general and
easy-to-use Python D-Bus bindings, which are similarly available in
other high-level languages.
So please consider that not all people like having to go down into the
machine room to make new plumbing with a C compiler. Having done too
much of that myself I can relate to them.
- Bert -
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