Commit c205991e authored by Tristan Van Berkom's avatar Tristan Van Berkom

doc/source/examples_flatpak_autotools.rst: Enhanced example

This has now changed to:

  * Have explanations of the project.conf and each element
    in the example, explaining what they are for

  * Have links into the reference for the specific features
    this example uses, such that the reader can get familiar
    with the reference manual from example windows
parent e6f59b63
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.. _examples_flatpak_autotools:
Using flatpak runtimes to build and run from source
Building on a Flatpak SDK
Here we demonstrate how to build and run software using
a Flatpak SDK for the base runtime.
Config files
- project.conf
Project structure
The following is a simple :ref:`project <projectconf>` definition:
.. literalinclude:: ../examples/flatpak-autotools/project.conf
:language: yaml
- element
Here we use an :ref:`arch option <project_options_arch>` to allow
conditional statements in this project to be made depending on machine
architecture. For this example we only support the ``i386`` and ``x86_64``
Note that we've added a :ref:`source alias <project_source_aliases>` for
the ```` repository to download the SDK from.
This is the :mod:`import <elements.import>` element used to import the
actual Flatpak SDK, it uses an :mod:`ostree <sources.ostree>` source to
download the Flatpak since these are hosted in OSTree repositories.
.. literalinclude:: ../examples/flatpak-autotools/elements/flatpak-autotools.bst
.. literalinclude:: ../examples/flatpak-autotools/elements/base/sdk.bst
:language: yaml
- element
While declaring the :mod:`ostree <sources.ostree>` source, we specify a GPG
public key to verify the OSTree download. This configuration is optional
but recommended for OSTree repositories. The key is stored in the project directory
at ``keys/gnome-sdk.gpg``.
We also use :ref:`conditional statements <format_directives_conditional>` to decide
which branch to download.
For the ``config`` section of this :mod:`import <elements.import>` element,
it's important to note two things:
* **source**: We only want to extract the ``files/`` directory from the SDK,
This is becase Flatpak runtimes dont start at the root of the OSTree checkout,
instead the actual files start in the ``files//`` subdirectory
.. literalinclude:: ../examples/flatpak-autotools/elements/dependencies/usrmerge.bst
* **target**: The content we've extracted should be staged at ``/usr``
This is because Flatpak runtimes only contain the data starting at ``/usr``,
and they expect to be staged at ``/usr`` at runtime, in an environment
with the appropriate symlinks setup from ``/``.
This is another :mod:`import <elements.import>` element, and it uses
the :mod:`local <sources.local>` source type so that we can stage files
literally stored in the same repository as the project.
.. literalinclude:: ../examples/flatpak-autotools/elements/base/usrmerge.bst
:language: yaml
The purpose of this element is simply to add the symlinks for
``/lib -> /usr/lib``, ``/bin -> /usr/bin`` and ``/etc -> /usr/etc``, we
have it depend on the ``base/sdk.bst`` element only to ensure that
it is staged *after*, i.e. the symlinks are created after the SDK is staged.
As suggested by the ``.bst`` file, the symlinks themselves are a part
of the project and they are stored in the ``files/links`` directory.
This is just a :mod:`stack <elements.stack>` element for convenience sake.
.. literalinclude:: ../examples/flatpak-autotools/elements/base.bst
:language: yaml
Often times you will have a more complex base to build things on, and it
is convenient to just use a :mod:`stack <elements.stack>` element for
your elements to depend on without needing to know about the inner workings
of the base system build.
Finally, we show an example of an :mod:`autotools <elements.autotools>` element
to build our sample "Hello World" program.
.. literalinclude:: ../examples/flatpak-autotools/elements/hello.bst
:language: yaml
We use another :mod:`local <sources.local>` source to obtain the sample
autotools project, but normally you would probably use a :mod:`git <sources.git>`
or other source to obtain source code from another repository.
Using the project
Now that we've explained the basic layout of the project, here are
just a few things you can try to do with the project.
.. note::
The following examples assume that you have first changed your working
directory to the project root.
This example is a part of the BuildStream source repository in
the doc/examples/flatpak-autotools subdirectory.
Build the hello.bst element
To build the project, run :ref:`bst build <invoking_build>` in the
following way::
bst build hello.bst
bst build flatpak-autotools.bst
Run the hello world program
The hello world program has been built into the standard ``/usr`` prefix,
and will automatically be in the default ``PATH`` for running things
in a :ref:`bst shell <invoking_shell>`.
bst shell flatpak-autotools.bst hello
To just run the program, run :ref:`bst shell <invoking_shell>` in the
following way::
bst shell hello.bst -- hello
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