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Python bindings for the Qt Framework.

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  1. 1. PySide Python Bindings for the Qt Framework Marcelo Lira - setanta March, 10th / Manaus - AM
  2. 2. Prologue
  3. 3. Who Am I? • Paid Open Source developer (lucky me!) • Computer Engineering Undergrad • I like Python but code mostly in C++ (it’s the "binding developer paradox") • PySide / PyMaemo team member at INdT
  4. 4. Who We Are? • INdT - Instituto Nokia de Tecnologia • openBossa - INdT’s open source stream • Known projects: Canola, Carman, PyMaemo • Friends of Qt Development Frameworks / KDE
  5. 5. Qt Labs Americas • openBossa initiative • Development of Qt and KDE communities on the Americas
  6. 6. Python "Python is the best language ever invented!" -- me import antigravity
  7. 7. Qt Frameworks Cross-platform application development framework. A little while after Nokia’s acquisition of Trolltech Qt started being distributed under the LGPL license.
  8. 8. Today’s Topics • PySide • Binding Generation • Current Status • Future
  9. 9. PySide == Python + Qt PySide is how we call the Python bindings of the Qt Framework produced by INdT/openBossa/Qt Labs Americas and released under the LGPL license.
  10. 10. PySide Motivation Python bindings for Qt under the LGPL license, aligned with the new licensing of Qt. Make the Qt-Python bindings fit hand-in-glove on the Maemo platform and devices. Because we are the INdT.
  11. 11. PySide Overview • PySide: the thing that you import • libpyside: takes care of Qt signals/slots • libshiboken: helps interfacing Python with C++
  12. 12. Binding Assembly Line • Qt Headers: the basic information about Qt libraries comes from here. • Type System files: here the binding developer modifies the collected information to fit the Python language. • Handwritten code: code to handle the C++ idiosyncrasies that could appear.
  13. 13. And Why Not...? • Cython • ctypes • Swig • SIP • SMOKE • Boost.Python • My favorite technology...
  14. 14. Binding Generation
  15. 15. PySide Goals Besides delivering LGPL Python bindings for Qt, our other important goal was to deliver the complete binding factory. fishes + fishing rod or PySide + Binding Generator And we care about your fishing skills too, so we try to document every part of the system.
  16. 16. Binding C++ libraries Things one must take care in the binding business: • C++ object to Python wrapper association • Inheritance • Multiple inheritance and casting pointers • Implicit type conversions • Methods with multiple signatures • Protected methods • Function arguments that return values • Virtual method overrides • Object ownership
  17. 17. Shiboken • Shiboken is the binding generator used to create the PySide bindings. • It can generate bindings not only for Qt, but for any C++ library. • The word means nothing at all. I was trying to remember some name and instead of returning an empty string my brain made that up.
  18. 18. Shiboken Ok, if you really need a meaning... • Shi: Death • Bo: Something, someone or somewhere • Ken: Sword (Disclaimer: I don’t know Japanese.)
  19. 19. Binding Generator Pedigree
  20. 20. Boost.Python The code created by the first Python binding generator used Boost.Python as sugar coating over the C Python API. In the beginning it was good because: • Quick start • Runtime speed Nevertheless, there was a bad part that showed up later: • The size problem templates over templates over templates == huge binaries • Lack of flexibility indirect access to the C Python API became a problem when flexibility was needed.
  21. 21. Binding Assembly Line (Again) • API Extractor: collects information from library headers, merges it with the modifications and handwritten code defined in the type system description. • Generator Runner: dynamic loader of generator front-ends. • Shiboken: generator front-end that outputs CPython source code.
  22. 22. libshiboken Bindings generated with Shiboken will also need libshiboken (which is LGPL, by the way). libshiboken helps with: • Association of C++ objects with Python wrappers • Multiple inheritance • Implicit type conversions • Virtual method overrides • Object ownership
  23. 23. The Type System Description <typesystem package="sample"> <primitive-type name="int"/> <primitive-type name="Complex" target-lang-api-name="PyComplex"> <conversion-rule file="complex_conversions.h"/> <include file-name="complex.h" location="global"/> </primitive-type> <namespace-type name="SampleNamespace"/> <value-type name="Number" /> <value-type name="SimpleFile"> <modify-function signature="open()"> <modify-argument index="return"> <remove-argument/> </modify-argument> <inject-code class="target" position="end" file="simplefile_glue.cpp"/> </modify-function> </value-type> </typesystem>
  24. 24. Current Status
  25. 25. Getting Rid of Boost.Python Die Boost.Python! Die!
  26. 26. Working Qt Modules • QtCore • QtGui (almost done) • QtNetwork and QtSvg (community effort! Go cgoncalves!) • QtWebkit • QtTest
  27. 27. And Now What? • Bug Fixing A couple of important generator bugs must be fixed. • Release We intend to release the Shiboken generated PySide in a month from now.
  28. 28. Future
  29. 29. Better Generation Process Help others to help themselves. • A tool to quick start binding development. • A visual binding creation/editing tool. (Perhaps a QtCreator plugin.)
  30. 30. The Other Side Our focus is on Maemo but there are other worlds we care about. • Linux Distros: were taken care by the community (Cheers to odyx! And to chaz6 for the build patches.) • MacOS X: it needs a little love. Anyone with a good heart and a white laptop? • Microsoft Windows: some work is already done, but still needs love. Lovers?
  31. 31. Pythonization One of PySide requisites was to be API compatible with PyQt4. But we want to make PySide’s API more Pythonic. Great, but... what makes something Pythonic? What is good? What is right? What is real?
  32. 32. PSEPs PySide Enhancement Proposals • Inspired by Python’s PEPs. • Discussed with the community.
  33. 33. Questions?
  34. 34. Directions #pyside at Freenode Marcelo Lira (setanta)
  35. 35. Thanks :)