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176091f Jul 19, 2016
@tsaunier @aleb
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Hacking on Pitivi

The Pitivi development environment

Setup Pitivi

The official way of getting your environment up and running is by using flatpak.

You first need to get flatpak making sure you also install flatpak-builder, which might be provided by an additional package on some distributions (please tell us if it is the case for yours so we can make a list here).

Create a development environment folder and get the Pitivi source code into it:

$ mkdir pitivi-dev && cd pitivi-dev
$ git clone https://git.gnome.org/browse/pitivi
$ cd pitivi/

Finally to enter the dev env you just need to run:

$ source bin/pitivi-env

Run pitivi while inside the environment to launch Pitivi. Next you should run the unittests.

(ptv-flatpak) $ pitivi
(ptv-flatpak) $ make check

After you hack the source code simply run pitivi again to see how your changes work.

Update the environment

To update the dependencies installed in the dev env run:

(ptv-flatpak) $ ptvenv --update

That will actually clean the prefix, update all dependencies from their git repos and tarballs as defined in the flatpak manifest (located at build/flatpak/pitivi.template.json)

Work on some Pitivi dependencies in the development environment

If you have to work on say, GStreamer Editing Services you can clone it into your pitivi-dev folder:

(ptv-flatpak) $ git clone git://anongit.freedesktop.org/gstreamer/gst-editing-services

Install it in the sandbox by running in the dev env:

(ptv-flatpak) $ autogen
(ptv-flatpak) $ make install

autogen is an alias which runs ./autogen.sh with the right arguments for the flatpak sandbox. make is also an alias which runs the real make inside the sandbox, thus make install will install your changes in the sandbox.

NOTE: When updating the environment, it will use your local dependencies repositories instead of remote repositories, which means you have to update them yourself. Also beware that it will not take into account not committed changes.

Coding Style Guide

We rely on the Python Style Guide PEP-8

The only exception to it is regarding the "80 columns" rule. Since Python is a very concise/compact language, we can afford to be a little bit more flexible on the line length than languages such as C.

When deciding whether or not you should split your line when it exceeds 79 characters, ask yourself: "Does it truly improve legibility?"

What this translates to is:

  • Avoid having very long lines.

  • When the contents only slightly exceeds the 80 chars limit, consider keeping it on one line. Otherwise it just hurts legibility and gives a weird "shape" to the code.

Names

The function names, method names and other class attributes should be small_caps_with_underscore. For example:

def some_function():
    return ""

class MyClass:

    def a_really_important_method(self):
        self.do_something()

    @property
    def water_level(self):
        """The level of the water in meters."""
        return self.__water_level

To illustrate how private a method or other class field is, prepend one or two underscores:

  class MyClass:

     def public_method(self):
         ...

     def _protected_method(self):
         ...

     def __private_method(self):
         ...

Unused arguments in methods should be prefixed with unused_. The most common place where this would happen is in callbacks from gobject signals. For example, below we don't use the second argument, but we do use pad.

     def __pad_added_cb(self, unused_element, pad):
        self.do_something_with(pad)

The name of a callback method should:

  • be prepended with two underscores since it's private
  • be appended with cb
  class MyClass:

     def some_method(self):
         self.someobject.connect('event', self.__some_object_event_cb)

     def __some_object_event_cb(self, object, arg):
         print "our callback was called"

Imports order

You can guess the order of the imported modules by looking at some py files. The pre-commit hook has authority in this case as it will reorder the imports if the order is not good.