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Re: On Contractor and Luna


Hey guys,

We have a lot of progress to report! Thanks to Michael Lazarski, Akshay
Shekher and Tom Beckmann we now have a working implementation of Contractor
daemon using the new API. It's already much less buggy than the older one.

Akshay has also transitioned Granite's wrapper to Contractor D-bus API to
the new API, it just needs one final round of review:
As soon as that's merged I'll land the new Contractor to the daily PPA.

He has also transitioned the Contractor widgets to the new API, but Dan
doesn't want any widgets interfacing with Contractor in Granite, so the
merge request deprecates them instead of updating them.

All that's left is to document the API (unfortunately the old Contractor
API is undocumented too) and to transition applications to the new API.
It's easy and will instantly fix multiple bugs (e.g. Scratch printing
problems Cassidy complained about).

2013/3/30 Sergey "Shnatsel" Davidoff <sergey@xxxxxxxxxxxxxxxx>

> Hey guys,
> I have some unpleasant things to bring up. Sorry for the long post, I hope
> it will not end up being another "TL;DR". (Come on, this is important!)
> As I've already reported, the current Contractor API is flawed. It relies
> on the client app calling Process.spawn_command_line_async<http://www.valadoc.org/#!api=glib-2.0/GLib.Process.spawn_command_line_async>on the string Contractor returns, which is bad for a long list of reasons.
> The most apparent one is being unable to handle filenames with spaces in
> them <https://bugs.launchpad.net/contractor/+bug/1123040>! This
> particular bug can be worked around in Contractor in an ugly way, but other
> issues remail and the API is not future-proof, so *we'll have to break it
> and Granite API/ABI* sooner or later (because Granite provides widgets
> and convenience functions for accessing Contractor API). Obviously it's
> better done sooner than later, while we don't have much code to transition
> and before the relevant Granite widgets get into a stable release.
> The more future-proof approach is to return a contract identifier to the
> client app and make the app call Contractor again to execute an action,
> passing it the identifier and the filename. This way Contractor can use
> proper process-launching functions or use completely different last-mile
> data transfer mechanisms<https://docs.google.com/document/d/1_w6-XBtr9qXXteytC9Mz0JqXZZoMsOPdfTDXVcoswUY/edit#>,
> so we'll be able to add support for streaming data without writing it to
> disk or invoking D-bus methods, all without breaking the API in the future.
> I've investigated the problems of the current Contractor and wrote a
> better specification<https://docs.google.com/a/elementaryos.org/document/d/1Ijsc57vYEHBZxVdM0fRgCuBX2NbdRDv1kuOj0OG75v4/edit#>,
> detailing its expected behavior and the required API changes. I've
> discussed it with the original Python Contractor authors and got the green
> light from them. Michael Lazarski (lampe2) has taken a stab at cleaning up
> Ammonkey's code and implementing the spec, but he's currently preoccupied
> by contracted work (no pun intended). His Contractor branch can be found at
> lp:contractor<https://code.launchpad.net/~michael.lazarski/contractor/master>
> .
> Additionally, I've looked into the state of Contractor support in Granite
> and elementary applications. In short, it's not glamorous.
> None of the apps use the Granite-provided ContractorMenu widget for the
> "Export" button; every single app reinvents the wheel and populates regular
> GTK menu with items acquired from Granite's Contractor wrapper. Maya (the
> least ugly implementation I've seen so far) even has a dedicated widget
> that's a clone of ContractorMenu!
> The other Contractor widget, ContractorView, is used only by Eidete where
> it doesn't seem to work; not sure if that's Contractor's fault or Eidete's.
> Finally, I don't understand why Granite has a wrapper for Contractor - it
> doesn't seem to reduce complexity or abstract anything. Using the D-bus API
> directly requires almost the same amount of code.
> So IMO the proper course of action is the following:
>  * Rework Contractor's D-bus API according to my specification<https://docs.google.com/a/elementaryos.org/document/d/1Ijsc57vYEHBZxVdM0fRgCuBX2NbdRDv1kuOj0OG75v4/edit?pli=1>
>  * Deprecate/abolish the Contractor wrapper in Granite
>  * Update Granite widgets and Pantheon Files to work with the new D-bus API
>  * Migrate other applications to using the Granite widgets (currently
> Maya, Scratch, Midori and elementary-flavored Simple Scan)
> However, I'm not sure this course of action is feasible for Luna.
> I'm absolutely not OK with releasing Granite with an API so flawed and
> which we're going to break in the future, so the alternative is to replace
> the current Contractor wrapper functions with stubs, mark them deprecated
> and replace Granite functionality in apps with something else.
> The options that spring to mind are:
>  * Replace Contractor actions with "Open With"
>  * Replace Contractor actions with a roughly similar but severely limited
> nautilus-sendto. Despite its name it's not actually related to Nautilus.
> This way we get sending files by bluetooth, email and IM; the catch is that
> Geary is not supported by nautilus-sendto, so we'll have to implement it
> (it should be done sooner or later for decent integration with Ubuntu).
>  * Remove the "Export" button from apps altogether
> Thoughts?
> --
> Sergey "Shnatsel" Davidoff
> OS architect @ elementary

Sergey "Shnatsel" Davidoff
OS architect @ elementary

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