Table Of Contents
Google Summer of Code - 2017¶
Introduction¶
Kivy is a cross-platform, business friendly, GPU accelerated open source Python library for rapid development of applications that make use of innovative user interfaces, such as multi-touch apps.
The Kivy Organization oversees several major projects:
The Kivy GUI Library
The Python-For-Android compilation tool.
The Kivy-iOS compilation tool.
The PyJNIus library for interfacing with Java from Python.
The PyOBJus library for interfacing with Objective-C from Python.
The Plyer platform-independent Python wrapper for platform dependent APIs.
Buildozer - A generic Python packager for Android, iOS, and desktop.
KivEnt - A 2d Game Engine that provides optimized methods of handling large amounts of dynamic visual data.
Kivy Designer - A graphical GUI designer for Kivy built in Kivy.
Altogether, these projects allow the user to create applications for every major operating system that make use of any native APIs present. Our goal is to enable development of Python applications that run everywhere off the same codebase and make use of platform dependent APIs and features that users of specific operating systems have come to expect.
Depending on which project you choose you may need to know Cython, OpenGL ES2, Java, Objective-C, or C in addition to Python. We make heavy use of Cython and OpenGL for computational and graphics performance where it matters, and the other languages are typically involved in accessing OS or provider level APIs.
We are hoping to participate in Google Summer of Code 2017. This page showcases some ideas for GSoC projects and corresponding guidelines for students contributing to the Kivy Framework.
Requirements¶
It is assumed that the incoming student meets some basic requirements as highlighted here:
Intermediate level familiarity with Python.
Comfortable with git and github (Kivy and its sister projects are all managed on github) If you have never used github before you may be interested in this tutorial.
Comfortable with event driven programming.
Has suitable tools/environment for Kivy or the sister project you are going to work on. For example to be able to work on PyOBJus you would need access to an iOS device, OS X with Xcode and a developer license, to work on PyJNIus you would need an Android device, and to work on plyer you would need access to hardware for both platforms.
Additional desired skills may be listed with specific projects.
Familiarize yourself with the contribution guide We can help you get up to speed, however students demonstrating ability in advance will be given preference.
How to get started¶
For Kivy, the easiest way is to follow the installation instructions for the development version for your specific platform:
http://kivy.org/docs/installation/installation.html#development-version
For the rest it’s usually sufficient to install the relevant project from git and add it to your PYTHONPATH.
e.g. for PyJNIus:
git clone http://github.com/kivy/pyjnius
export PYTHONPATH=/path/to/pyjnius:$PYTHONPATH
Project Ideas¶
Here are some prospective ideas sourced from the Kivy development team, if none of these projects interest you come talk to us in #kivy-dev about a project idea of your own.
Beginner Projects¶
These projects should be suitable for anyone with a college level familiarity with Python and require little knowledge of platform specifics.
Intermediate Projects¶
These projects may involve cursory level knowledge of several OS level details, some OpenGL interaction, or other topics that may be a bit out of the wheelhouse of the average Pythonista.
Plyer:
- Description:
Plyer is a platform-independent Python API to use features commonly found on the desktop and mobile platforms supported by Kivy. The idea is to provide a stable API to the user for accessing features of their desktop or mobile device.
The student would replace some .java code currently in the p4a project to a more appropriate place in Plyer. In addition, the student would work on improving access to platform specific features through Plyer, including accessibility, Bluetooth Low Energy, accessing and editing contacts, sharing, NFC, in-app browser, Wi-Fi (enable, disable, access to Wi-Fi services (Wi-Fi direct, network accessibility, current IP info on network etc.), Camera capture (video), camera display, Google Play integration, launch phone call interface, sms interface, geolocation, interaction with notifications, internationalization (I18N), and all the missing platform implementations from existing features.
Under the hood you’ll use PyJNIus on Android, PyOBJus on OS X and iOS, ctypes on Windows, and native APIs on Linux. This probably would also include improving PyOBJus and PyJNIus to handle interfaces that they can’t right now.
- References:
- Expected outcome:
A successful outcome would include moving the Java/PyOBJus code from p4a/kivy-ios to plyer and implementing some or all of the new facades to be decided with the student.
Mentors: Akshay Arora
Requirements: Access to Linux, Windows, OS X, iOS device, Android device.
Task level: Intermediate
Desired Skills: Familiarity with PyJNIus, PyOBJus.
Font Reshaping and Font Fallback Support
- Description:
Currently Kivy does not support reshaping for alphabets such as Arabic, Persian, Thai, or Devanagari. The solution is to integrate a text shaping and layout engine (Pango and Harfbuzz). You would need to ensure that Pango and Harfbuzz can be compiled on every platform, and integrate it as a core text provider.
The second part of the same project would involve font fallback support. If a particular character/glyph is missing, currently we show a [] box. The solution for this would involve either using an OS API if available or maintaining a hashtable for the default fonts on each OS which can be used for glyph fallback.
- References:
- Expected outcome:
Font fallback and text reshaping support in Kivy, compilation recipes for Python-For-Android and packaging on desktop platforms.
Mentors: Akshay Arora, Jacob Kovac, Matthew Einhorn
Requirements: Access to a desktop OS and ideally at least one mobile platform
Task level: Intermediate
Desired Skills: Familiarity with text rendering, Pango, HarfBuzz and Kivy’s provider abstraction.
Advanced Projects¶
These projects may involve very in-depth knowledge of Kivy’s existing internals, the hairy details of cross-platform compilation, or other fairly advanced topics. If you are comfortable with the internals of Python, working with C code, and using Cython to build your own C extensions these projects may appeal to you.
Kivent: Chipmunk 7 Integration
- Description:
KivEnt is a modular entity-component based game engine built on top of Kivy. KivEnt provides a highly performant approach to building games in Python that avoids some of the worst overhead of Python using specialized Cython constructs.
At the moment, KivEnt internally makes use of the cymunk library (https://github.com/tito/cymunk) for physics simulation and collision detection. Cymunk is based on Chipmunk2d 6.x, recently Chipmunk 7 has released and brought many previously premium features into the core library. In addition to the API changes present in the newest Chipmunk, the KivEnt - Cymunk bridging does not make most efficient use of the KivEnt API for handling C level objects and data. The student will be responsible for creating a new wrapper over Chipmunk2d 7 that better matches KivEnt’s approach to handling game data.
- References:
- Expected Outcome:
A successful outcome involves a new kivent_tiled module being released for the KivEnt game engine.
Mentors: Jacob Kovac
Requirements: Access to at least one Kivy platform.
Task level: Advanced
Desired Skills: Familiarity with Cython, Python, and game dev related math concepts.
KV Compiler: A compiler for the KV language
- Description:
The KV language is a fundamental component of Kivy. The KV language allows one to describe a GUI; from the creation of a Widget tree to the actions that should be taken in response value changes and events. In effect it is a concise way to create rule bindings using the Kivy properties and events. Internally, python code that reflects these rules are created and bound to the properties and events. Currently, these bindings are not at all optimized because upon each widget creation all of these rules are re-evaluated and bound. This process can be significantly optimized by pre-compiling the kv code, especially the bindings. A compiler would also allow us to update and fix some of the long-standing kv language issues.
Work on a kv-compiler has already progressed quite far, in fact a PR in the pre-alpha stage, is currently open. However, it is out of sync with the current codebase due to some unrelated kv changes in the meantime. Also, that PR would require a significant re-write to make things more modular, self-contained, and extensible. So there is much work still to be done on it.
Theming has also been a prepatual issue in Kivy, a KV compiler may help implement bindings that facilitate theming.
- References:
- Expected Outcome:
A successful outcome would be a compiler which compiles kv code into python code. The compiler should be modular and extensible so that we can continue to improve the kv language. The compiler should have the common debug/optimization options. The compiled code should also be human readable so issues could be traced back to the original kv code. The compiler should also be a drop in replacement for the current KV runtime compiler, and would require extensive testing.
Mentors: Matthew Einhorn
Requirements: Access to at least one Kivy platform.
Task level: Advanced
Desired Skills: Familiarity with Cython, Python, and Kivy. Familiarity with typical computer science concepts and data structures is also desired.
How to Contact devs¶
All communication must happen via public channels, private emails and Discord private messages are discouraged.
Ask your questions on the Kivy Users forum https://groups.google.com/group/kivy-users or send a mail at kivy-users@googlegroups.com
Make sure to join the kivy-dev user group too: https://groups.google.com/forum/#!forum/kivy-dev.
You can also try to contact us on Discord, to get the Discord handles of the devs mentioned above visit https://kivy.org/#aboutus.
Make sure to read the Discord rules before connecting. Connect to Discord.
Most of our developers are located in Europe, India, and North America so keep in mind typical waking hours for these areas.
How to be a good student¶
If you want to participate as a student and want to maximize your chances of being accepted, start talking to us today and try fixing some smaller problems to get used to our workflow. If we know you can work well with us, you will have much better chances of being selected.
Here’s a checklist:
Make sure to read through the website and at least skim the documentation.
Look at the source code.
Read our contribution guidelines.
Make a contribution! Kivy would like to see how you engage with the development process. Take a look at the issue tracker for a Kivy project that interests you and submit a Pull Request. It can be a simple bug or a documentation change. We are looking to get a feel for how you work, not evaluating your capabilities. Don’t worry about trying to pick something to impress us.
Pick an idea that you think is interesting from the ideas list or come up with your own idea.
Do some research yourself. GSoC is about give and take, not just one sided interaction. It is about you trying to achieve agreed upon goals with our support. The main driving force in this should be, obviously, yourself. Many students pop up and ask what they should do. You should base that decision on your interests and your skills. Show us you’re serious about it and take the initiative.
Write a draft proposal about what you want to do. Include what you understand the current state of the project to be, what you would like to improve, how, etc.
Discuss that proposal with us in a timely manner. Get feedback.
Be patient! Especially on Discord. We will try to get to you if we’re available. If not, send an email and just wait. Most questions are already answered in the docs or somewhere else and can be found with some research. Your questions should reflect that you’ve actually thought through what you’re asking and done some rudimentary research.
Most of all don’t forget to have fun and interact with the community. The community is as big a part of Open Source as the code itself.
What to expect if you are chosen¶
All students should join the #support and the #dev Discord channels daily, this is how the development team communicates both internally and with the users.
You and your mentors will agree on two week milestones for the duration of the summer.
Development will occur in your fork of the master branch of Kivy, we expect you to submit at least one PR a week from your branch into a branch reserved for you in the primary repo. This will be your forum for reporting progress as well as documenting any struggles you may have encountered.
Missing 2 weekly PR or 2 milestones will result in your failure unless there have been extenuating circumstances. If something comes up, please inform your mentors as soon as possible. If a milestone seems out of reach we will work with you to reevaluate the goals.
Your changes will be merged into master once the project has been completed and we have thoroughly tested on every platform that is relevant.