Matplotlib depends on non-Python libraries.

On Linux and OSX, pkg-config_ can be used to find required non-Python

libraries and thus make the install go more smoothly if the libraries and

headers are not in the expected locations.

.. _pkg-config: https://www.freedesktop.org/wiki/Software/pkg-config/

If not using pkg-config (in particular on Windows), you may need to set the

include path (to the FreeType, libpng, and zlib headers) and link path (to

the FreeType, libpng, and zlib libraries) explicitly, if they are not in

standard locations. This can be done using standard environment variables

-- on Linux and OSX:

.. code-block:: sh

and on Windows:

.. code-block:: bat

where ``...`` means "also give, in the same format, the directories

containing ``png.h`` and ``zlib.h`` for the include path, and for

``libpng.so``/``png.lib`` and ``libz.so``/``z.lib`` for the link path."

Changes to search paths for FreeType and libpng

The ``MPLBASEDIRLIST`` environment variables and ``basedirlist`` entry in

``setup.cfg`` have no effect anymore. Instead, if building in situations where

FreeType or libpng are not in the compiler or linker's default path, set the

standard environment variables ``CFLAGS``/``LDFLAGS`` on Linux or OSX, or

``CL``/``LINK`` on Windows, to indicate the relevant paths.

See details in :file:`INSTALL.rst`.

flags = shlex.split(

# Use sys.getfilesystemencoding() to allow round-tripping

# when passed back to later subprocess calls, not

# locale.getpreferredencoding() which

# universal_newlines=True would do.

os.fsdecode(

subprocess.check_output([*cmd, "--cflags", "--libs"])))