PySide Binding Generation Tutorial: Module 5 Building the generator

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• Note: this article is a member of the multipart PySide Binding Generation Tutorial [developer.qt.nokia.com]

PySide Binding Generation Tutorial

Three Steps to Build the Binding

As mentioned before, the build system used must perform the following tasks in the correct order:

• Gather data about locations of headers and needed type systems from other projects.
• Run the generator with the correct parameters.
• Compile and link the binding.

Gather Information

There are two options to gather data about locations of headers and needed type systems:

Collect Information with pkg-config

The Qt bindings include compile and build information through the pkg-config mechanism. The pkg-config name for Qt Python bindings is

pyside

and a simple

pkg-config pyside —cflags —libs

will retrieve information required to build the new binding. The Qt bindings file

pyside.pc

for the use of pkg-config requires Qt’s

.pc

files to be installed. If the library is in an unusual location, e.g.

/opt/qt47

, remember to export it to the

<span class="caps">PKG</span>_CONFIG_PATH

environment variable. For example:

export <span class="caps">PKG</span>_CONFIG_PATH=$PKG_CONFIG_PATH:/opt/qt47/lib/pkgconfig

Information is also available through pkg-config: the

typesystemdir

variable. It is used like this:

pkg-config pyside —variable=typesystemdir

This provides information where to find the type system files used to create the Qt bindings. As mentioned before, the binding being created needs this to complement its own binding information for the generation proccess. Information from the Shiboken binding generator is also needed for the build, it’s pkg-config name is

shiboken

. More details on this later.

Collect Information with CMake

When building your binding with CMake the relevant information can be included from your project’s

CMakeLists.txt

using: Similarly

ShibokenConfig.cmake

provides needed information:

Run the Generator

The generator is called with the following parameters and options:

Note that the variables for include and type system paths could be determined at build time with the pkg-config tool or with information provided by CMake configuration files.

Build

This section will alternate in presenting the two build methods: Makefile and CMake.

The Makefile Version

Below is a plain Makefile for the binding project.

foobinding-makefile/Makefile

: Keep in mind that the Makefile above expects the

libfoo

and

foobinding-makefile

directories to be in the same level in the directory hierarchy. Remember to change any path references accordingly if you elect to change things.

Build and Test

Now generate, compile and link the binding with make:

The

make test

causes the Python interpreter to run the line

import foo; m = foo.Math(); print ’5 squared is %d’ % m.squared(5)

, which will import the binding module, instantiate the class from it, run a method and print its result (which should be 25).

The CMake Version

foobinding-cmake/CMakeLists.txt

: This is the main project’s

CMakeLists.txt

, it is a regular CMake file and general doubts can be checked in the CMake documentation [cmake.org] Notice the we’re going to have tests in this project so we have to enable them with

enable_testing()

.

foobinding-cmake/foo/CMakeLists.txt

: This is the

CMakeLists.txt

file for the binding directory proper, the

add_custom_command

statement is responsible for the calling of Shiboken generator with the proper parameters and variables. Notice that the command line options

—enable-parent-ctor-heuristic —enable-pyside-extensions —enable-return-value-heuristic

are directly related to Qt bindings idiosyncrasies, for a pure C++ binding none of those will be necessary.

foobinding-cmake/tests/CMakeLists.txt

: This not very elaborate

CMakeLists.txt

informs CMake which tests should be executed, and with which variables.

Build and Test

The best thing to do when building with CMake is to create a build directory and run

cmake

from there.

Ah, let’s not forget the unit test. It’s a very simple one.

foobinding-cmake/tests/math.py

To run the test:

The output will be something like this:

For a more verbose output use

ctest -V

Conclusion

That’s pretty much it. More examples of CMakeLists.txt files and binding unit tests check the PySide sources [qt.gitorious.org].

Categories:

• LanguageBindings
  • PySide
• Shiboken

• PySide_Binding_Generation_Tutorial