setupext.py

import configparser
from distutils import ccompiler, sysconfig
from distutils.core import Extension
import functools
import glob
import hashlib
from io import BytesIO
import logging
import os
import pathlib
import platform
import shlex
import shutil
import subprocess
import sys
import tarfile
import textwrap
import urllib.request
from urllib.request import Request
import versioneer

_log = logging.getLogger(__name__)


def _get_xdg_cache_dir():
    """
    Return the XDG cache directory.

    See https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
    """
    cache_dir = os.environ.get('XDG_CACHE_HOME')
    if not cache_dir:
        cache_dir = os.path.expanduser('~/.cache')
        if cache_dir.startswith('~/'):  # Expansion failed.
            return None
    return pathlib.Path(cache_dir, 'matplotlib')


def get_fd_hash(fd):
    """
    Compute the sha256 hash of the bytes in a file-like
    """
    BLOCKSIZE = 1 << 16
    hasher = hashlib.sha256()
    old_pos = fd.tell()
    fd.seek(0)
    buf = fd.read(BLOCKSIZE)
    while buf:
        hasher.update(buf)
        buf = fd.read(BLOCKSIZE)
    fd.seek(old_pos)
    return hasher.hexdigest()


def download_or_cache(url, sha):
    """
    Get bytes from the given url or local cache.

    Parameters
    ----------
    url : str
        The url to download

    sha : str
        The sha256 of the file

    Returns
    -------
    BytesIO
        The file loaded into memory.
    """
    cache_dir = _get_xdg_cache_dir()

    def get_from_cache(local_fn):
        if cache_dir is None:
            raise Exception("no cache dir")
        buf = BytesIO((cache_dir / local_fn).read_bytes())
        if get_fd_hash(buf) != sha:
            return None
        buf.seek(0)
        return buf

    def write_cache(local_fn, data):
        if cache_dir is None:
            raise Exception("no cache dir")
        cache_dir.mkdir(parents=True, exist_ok=True)
        old_pos = data.tell()
        data.seek(0)
        with open(cache_dir / local_fn, "xb") as fout:
            fout.write(data.read())
        data.seek(old_pos)

    try:
        return get_from_cache(sha)
    except Exception:
        pass

    # jQueryUI's website blocks direct downloads from urllib.request's
    # default User-Agent, but not (for example) wget; so I don't feel too
    # bad passing in an empty User-Agent.
    with urllib.request.urlopen(
            Request(url, headers={"User-Agent": ""})) as req:
        file_contents = BytesIO(req.read())
        file_contents.seek(0)

    file_sha = get_fd_hash(file_contents)

    if file_sha != sha:
        raise Exception(
            f"The download file does not match the expected sha.  {url} was "
            f"expected to have {sha} but it had {file_sha}")

    try:
        write_cache(sha, file_contents)
    except Exception:
        pass

    file_contents.seek(0)
    return file_contents


# SHA256 hashes of the FreeType tarballs
_freetype_hashes = {
    '2.6.1':
        '0a3c7dfbda6da1e8fce29232e8e96d987ababbbf71ebc8c75659e4132c367014',
    '2.6.2':
        '8da42fc4904e600be4b692555ae1dcbf532897da9c5b9fb5ebd3758c77e5c2d4',
    '2.6.3':
        '7942096c40ee6fea882bd4207667ad3f24bff568b96b10fd3885e11a7baad9a3',
    '2.6.4':
        '27f0e38347a1850ad57f84fc4dfed68ba0bc30c96a6fa6138ef84d485dd9a8d7',
    '2.6.5':
        '3bb24add9b9ec53636a63ea8e867ed978c4f8fdd8f1fa5ccfd41171163d4249a',
    '2.7':
        '7b657d5f872b0ab56461f3bd310bd1c5ec64619bd15f0d8e08282d494d9cfea4',
    '2.7.1':
        '162ef25aa64480b1189cdb261228e6c5c44f212aac4b4621e28cf2157efb59f5',
    '2.8':
        '33a28fabac471891d0523033e99c0005b95e5618dc8ffa7fa47f9dadcacb1c9b',
    '2.8.1':
        '876711d064a6a1bd74beb18dd37f219af26100f72daaebd2d86cb493d7cd7ec6',
    '2.9':
        'bf380e4d7c4f3b5b1c1a7b2bf3abb967bda5e9ab480d0df656e0e08c5019c5e6',
    '2.9.1':
        'ec391504e55498adceb30baceebd147a6e963f636eb617424bcfc47a169898ce',
    '2.10.0':
        '955e17244e9b38adb0c98df66abb50467312e6bb70eac07e49ce6bd1a20e809a',
    '2.10.1':
        '3a60d391fd579440561bf0e7f31af2222bc610ad6ce4d9d7bd2165bca8669110',
}
# This is the version of FreeType to use when building a local
# version.  It must match the value in
# lib/matplotlib.__init__.py and also needs to be changed below in the
# embedded windows build script (grep for "REMINDER" in this file)
LOCAL_FREETYPE_VERSION = '2.6.1'
LOCAL_FREETYPE_HASH = _freetype_hashes.get(LOCAL_FREETYPE_VERSION, 'unknown')


# matplotlib build options, which can be altered using setup.cfg
options = {
    'backend': None,
    'staticbuild': False,
    }


setup_cfg = os.environ.get('MPLSETUPCFG', 'setup.cfg')
if os.path.exists(setup_cfg):
    config = configparser.ConfigParser()
    config.read(setup_cfg)

    if config.has_option('rc_options', 'backend'):
        options['backend'] = config.get("rc_options", "backend")

    if config.has_option('test', 'local_freetype'):
        options['local_freetype'] = config.getboolean("test", "local_freetype")

    if config.has_option('build', 'staticbuild'):
        options['staticbuild'] = config.getboolean("build", "staticbuild")
else:
    config = None

lft = bool(os.environ.get('MPLLOCALFREETYPE', False))
options['local_freetype'] = lft or options.get('local_freetype', False)

staticbuild = bool(os.environ.get('MPLSTATICBUILD', os.name == 'nt'))
options['staticbuild'] = staticbuild or options.get('staticbuild', False)


if '-q' in sys.argv or '--quiet' in sys.argv:
    def print_raw(*args, **kwargs): pass  # Suppress our own output.
else:
    print_raw = print


def print_status(package, status):
    initial_indent = "%12s: " % package
    indent = ' ' * 18
    print_raw(textwrap.fill(str(status), width=80,
                            initial_indent=initial_indent,
                            subsequent_indent=indent))


def get_buffer_hash(fd):
    BLOCKSIZE = 1 << 16
    hasher = hashlib.sha256()
    buf = fd.read(BLOCKSIZE)
    while buf:
        hasher.update(buf)
        buf = fd.read(BLOCKSIZE)
    return hasher.hexdigest()


def deplib(libname):
    if sys.platform != 'win32':
        return libname

    known_libs = {
        # TODO: support versioned libpng on build system rewrite
        'libpng16': ('libpng16', '_static'),
        'z': ('zlib', 'static'),
    }

    libname, static_postfix = known_libs[libname]
    if options['staticbuild']:
        libname += static_postfix

    return libname


@functools.lru_cache(1)  # We only need to compute this once.
def get_pkg_config():
    """
    Get path to pkg-config and set up the PKG_CONFIG environment variable.
    """
    if sys.platform == 'win32':
        return None
    pkg_config = os.environ.get('PKG_CONFIG', 'pkg-config')
    if shutil.which(pkg_config) is None:
        print(
            "IMPORTANT WARNING:\n"
            "    pkg-config is not installed.\n"
            "    Matplotlib may not be able to find some of its dependencies.")
        return None
    pkg_config_path = sysconfig.get_config_var('LIBDIR')
    if pkg_config_path is not None:
        pkg_config_path = os.path.join(pkg_config_path, 'pkgconfig')
        try:
            os.environ['PKG_CONFIG_PATH'] += ':' + pkg_config_path
        except KeyError:
            os.environ['PKG_CONFIG_PATH'] = pkg_config_path
    return pkg_config


def pkg_config_setup_extension(
        ext, package,
        atleast_version=None, alt_exec=None, default_libraries=()):
    """Add parameters to the given *ext* for the given *package*."""

    # First, try to get the flags from pkg-config.

    pkg_config = get_pkg_config()
    cmd = [pkg_config, package] if pkg_config else alt_exec
    if cmd is not None:
        try:
            if pkg_config and atleast_version:
                subprocess.check_call(
                    [*cmd, f"--atleast-version={atleast_version}"])
            # Use sys.getfilesystemencoding() to allow round-tripping
            # when passed back to later subprocess calls; do not use
            # locale.getpreferredencoding() which universal_newlines=True
            # would do.
            cflags = shlex.split(
                os.fsdecode(subprocess.check_output([*cmd, "--cflags"])))
            libs = shlex.split(
                os.fsdecode(subprocess.check_output([*cmd, "--libs"])))
        except (OSError, subprocess.CalledProcessError):
            pass
        else:
            ext.extra_compile_args.extend(cflags)
            ext.extra_link_args.extend(libs)
            return

    # If that fails, fall back on the defaults.

    # conda Windows header and library paths.
    # https://github.com/conda/conda/issues/2312 re: getting the env dir.
    if sys.platform == 'win32':
        conda_env_path = (os.getenv('CONDA_PREFIX')  # conda >= 4.1
                          or os.getenv('CONDA_DEFAULT_ENV'))  # conda < 4.1
        if conda_env_path and os.path.isdir(conda_env_path):
            ext.include_dirs.append(os.fspath(
                pathlib.Path(conda_env_path, "Library/include")))
            ext.library_dirs.append(os.fspath(
                pathlib.Path(conda_env_path, "Library/lib")))

    # Default linked libs.
    ext.libraries.extend(default_libraries)


class CheckFailed(Exception):
    """
    Exception thrown when a `SetupPackage.check` method fails.
    """
    pass


class SetupPackage:
    optional = False

    def check(self):
        """
        Checks whether the build dependencies are met.  Should raise a
        `CheckFailed` exception if the dependency could not be met, otherwise
        return a string indicating a version number or some other message
        indicating what was found.
        """
        pass

    def get_package_data(self):
        """
        Get a package data dictionary to add to the configuration.
        These are merged into to the `package_data` list passed to
        `distutils.setup`.
        """
        return {}

    def get_extension(self):
        """
        Get a list of C extensions (`distutils.core.Extension`
        objects) to add to the configuration.  These are added to the
        `extensions` list passed to `distutils.setup`.
        """
        return None

    def do_custom_build(self):
        """
        If a package needs to do extra custom things, such as building a
        third-party library, before building an extension, it should
        override this method.
        """
        pass


class OptionalPackage(SetupPackage):
    optional = True
    force = False
    config_category = "packages"
    default_config = "auto"

    @classmethod
    def get_config(cls):
        """
        Look at `setup.cfg` and return one of ["auto", True, False] indicating
        if the package is at default state ("auto"), forced by the user (case
        insensitively defined as 1, true, yes, on for True) or opted-out (case
        insensitively defined as 0, false, no, off for False).
        """
        conf = cls.default_config
        if (config is not None
                and config.has_option(cls.config_category, cls.name)):
            try:
                conf = config.getboolean(cls.config_category, cls.name)
            except ValueError:
                conf = config.get(cls.config_category, cls.name)
        return conf

    def check(self):
        """
        Check whether ``setup.cfg`` requests this package to be installed.

        May be overridden by subclasses for additional checks.
        """
        # Check configuration file
        conf = self.get_config()
        # Default "auto" state or install forced by user
        if conf in [True, 'auto']:
            # Set non-optional if user sets `True` in config
            if conf is True:
                self.optional = False
            return "installing"
        # Configuration opt-out by user
        else:
            # Some backend extensions (e.g. Agg) need to be built for certain
            # other GUI backends (e.g. TkAgg) even when manually disabled
            if self.force is True:
                return "installing forced (config override)"
            else:
                raise CheckFailed("skipping due to configuration")


class OptionalBackendPackage(OptionalPackage):
    config_category = "gui_support"


class Platform(SetupPackage):
    name = "platform"

    def check(self):
        return sys.platform


class Python(SetupPackage):
    name = "python"

    def check(self):
        return sys.version


def _pkg_data_helper(pkg, subdir):
    """Glob "lib/$pkg/$subdir/**/*", returning paths relative to "lib/$pkg"."""
    base = pathlib.Path("lib", pkg)
    return [str(path.relative_to(base)) for path in (base / subdir).rglob("*")]


class Matplotlib(SetupPackage):
    name = "matplotlib"

    def check(self):
        return versioneer.get_version()

    def get_package_data(self):
        return {
            'matplotlib': [
                'mpl-data/matplotlibrc',
                *_pkg_data_helper('matplotlib', 'mpl-data/fonts'),
                *_pkg_data_helper('matplotlib', 'mpl-data/images'),
                *_pkg_data_helper('matplotlib', 'mpl-data/stylelib'),
                *_pkg_data_helper('matplotlib', 'backends/web_backend'),
                '*.dll',  # Only actually matters on Windows.
            ],
        }


class SampleData(OptionalPackage):
    """
    This handles the sample data that ships with matplotlib.  It is
    technically optional, though most often will be desired.
    """
    name = "sample_data"

    def get_package_data(self):
        return {
            'matplotlib': [
                *_pkg_data_helper('matplotlib', 'mpl-data/sample_data'),
            ],
        }


class Tests(OptionalPackage):
    name = "tests"
    default_config = False

    def get_package_data(self):
        return {
            'matplotlib': [
                *_pkg_data_helper('matplotlib', 'tests/baseline_images'),
                *_pkg_data_helper('matplotlib', 'tests/tinypages'),
                'tests/cmr10.pfb',
                'tests/mpltest.ttf',
            ],
            'mpl_toolkits': [
                *_pkg_data_helper('mpl_toolkits', 'tests/baseline_images'),
            ]
        }


def add_numpy_flags(ext):
    import numpy as np
    ext.include_dirs.append(np.get_include())
    ext.define_macros.extend([
        # Ensure that PY_ARRAY_UNIQUE_SYMBOL is uniquely defined for each
        # extension.
        ('PY_ARRAY_UNIQUE_SYMBOL',
         'MPL_' + ext.name.replace('.', '_') + '_ARRAY_API'),
        ('NPY_NO_DEPRECATED_API', 'NPY_1_7_API_VERSION'),
        # Allow NumPy's printf format specifiers in C++.
        ('__STDC_FORMAT_MACROS', 1),
    ])


class LibAgg(SetupPackage):
    name = 'libagg'

    def add_flags(self, ext, add_sources=True):
        # We need a patched Agg not available elsewhere, so always use the
        # vendored version.
        ext.include_dirs.insert(0, 'extern/agg24-svn/include')
        if add_sources:
            agg_sources = [
                'agg_bezier_arc.cpp',
                'agg_curves.cpp',
                'agg_image_filters.cpp',
                'agg_trans_affine.cpp',
                'agg_vcgen_contour.cpp',
                'agg_vcgen_dash.cpp',
                'agg_vcgen_stroke.cpp',
                'agg_vpgen_segmentator.cpp'
                ]
            ext.sources.extend(os.path.join('extern', 'agg24-svn', 'src', x)
                               for x in agg_sources)


# For FreeType2 and libpng, we add a separate checkdep_foo.c source to at the
# top of the extension sources.  This file is compiled first and immediately
# aborts the compilation either with "foo.h: No such file or directory" if the
# header is not found, or an appropriate error message if the header indicates
# a too-old version.


class FreeType(SetupPackage):
    name = "freetype"

    def add_flags(self, ext):
        ext.sources.insert(0, 'src/checkdep_freetype2.c')
        if options.get('local_freetype'):
            src_path = pathlib.Path(
                'build', f'freetype-{LOCAL_FREETYPE_VERSION}')
            # Statically link to the locally-built freetype.
            # This is certainly broken on Windows.
            ext.include_dirs.insert(0, str(src_path / 'include'))
            if sys.platform == 'win32':
                libfreetype = 'libfreetype.lib'
            else:
                libfreetype = 'libfreetype.a'
            ext.extra_objects.insert(
                0, str(src_path / 'objs' / '.libs' / libfreetype))
            ext.define_macros.append(('FREETYPE_BUILD_TYPE', 'local'))
        else:
            pkg_config_setup_extension(
                # FreeType 2.3 has libtool version 9.11.3 as can be checked
                # from the tarball.  For FreeType>=2.4, there is a conversion
                # table in docs/VERSIONS.txt in the FreeType source tree.
                ext, 'freetype2',
                atleast_version='9.11.3',
                alt_exec=['freetype-config'],
                default_libraries=['freetype', deplib('z')])
            ext.define_macros.append(('FREETYPE_BUILD_TYPE', 'system'))

    def do_custom_build(self):
        # We're using a system freetype
        if not options.get('local_freetype'):
            return

        src_path = pathlib.Path('build', f'freetype-{LOCAL_FREETYPE_VERSION}')

        # We've already built freetype
        if sys.platform == 'win32':
            libfreetype = 'libfreetype.lib'
        else:
            libfreetype = 'libfreetype.a'

        # bailing because it is already built
        if (src_path / 'objs' / '.libs' / libfreetype).is_file():
            return

        # do we need to download / load the source from cache?
        if not src_path.exists():
            os.makedirs('build', exist_ok=True)

            url_fmts = [
                ('https://downloads.sourceforge.net/project/freetype'
                 '/freetype2/{version}/{tarball}'),
                ('https://download.savannah.gnu.org/releases/freetype'
                 '/{tarball}')
            ]
            tarball = f'freetype-{LOCAL_FREETYPE_VERSION}.tar.gz'

            target_urls = [
                url_fmt.format(version=LOCAL_FREETYPE_VERSION,
                               tarball=tarball)
                for url_fmt in url_fmts]

            for tarball_url in target_urls:
                try:
                    tar_contents = download_or_cache(tarball_url,
                                                     LOCAL_FREETYPE_HASH)
                    break
                except Exception:
                    pass
            else:
                raise IOError(
                    f"Failed to download FreeType. Please download one of "
                    f"{target_urls} and extract it into {src_path} at the "
                    f"top-level of the source repository.")

            print(f"Extracting {tarball}")
            # just to be sure
            tar_contents.seek(0)
            with tarfile.open(tarball, mode="r:gz",
                              fileobj=tar_contents) as tgz:
                tgz.extractall("build")

        print(f"Building freetype in {src_path}")
        if sys.platform != 'win32':  # compilation on non-windows
            env = {**os.environ,
                   "CFLAGS": "{} -fPIC".format(os.environ.get("CFLAGS", ""))}
            subprocess.check_call(
                ["./configure", "--with-zlib=no", "--with-bzip2=no",
                 "--with-png=no", "--with-harfbuzz=no"],
                env=env, cwd=src_path)
            subprocess.check_call(["make"], env=env, cwd=src_path)
        else:
            # compilation on windows
            shutil.rmtree(str(pathlib.Path(src_path, "objs")),
                          ignore_errors=True)
            msbuild_platform = (
                'x64' if platform.architecture()[0] == '64bit' else 'Win32')
            base_path = pathlib.Path("build/freetype-2.6.1/builds/windows")
            vc = 'vc2010'
            sln_path = (
                base_path / vc / "freetype.sln"
            )
            # https://developercommunity.visualstudio.com/comments/190992/view.html
            (sln_path.parent / "Directory.Build.props").write_text("""
<Project>
 <PropertyGroup>
  <!-- The following line *cannot* be split over multiple lines. -->
  <WindowsTargetPlatformVersion>$([Microsoft.Build.Utilities.ToolLocationHelper]::GetLatestSDKTargetPlatformVersion('Windows', '10.0'))</WindowsTargetPlatformVersion>
 </PropertyGroup>
</Project>
""")
            cc = ccompiler.new_compiler()
            cc.initialize()  # Get devenv & msbuild in the %PATH% of cc.spawn.
            cc.spawn(["devenv", str(sln_path), "/upgrade"])
            cc.spawn(["msbuild", str(sln_path),
                      "/t:Clean;Build",
                      f"/p:Configuration=Release;Platform={msbuild_platform}"])
            # Move to the corresponding Unix build path.
            (src_path / "objs" / ".libs").mkdir()
            # Be robust against change of FreeType version.
            lib_path, = (src_path / "objs" / vc / msbuild_platform).glob(
                "freetype*.lib")
            shutil.copy2(lib_path, src_path / "objs/.libs/libfreetype.lib")


class FT2Font(SetupPackage):
    name = 'ft2font'

    def get_extension(self):
        sources = [
            'src/ft2font.cpp',
            'src/ft2font_wrapper.cpp',
            'src/mplutils.cpp',
            'src/py_converters.cpp',
            ]
        ext = Extension('matplotlib.ft2font', sources)
        FreeType().add_flags(ext)
        add_numpy_flags(ext)
        LibAgg().add_flags(ext, add_sources=False)
        return ext


class Png(SetupPackage):
    name = "png"

    def get_extension(self):
        sources = [
            'src/checkdep_libpng.c',
            'src/_png.cpp',
            'src/mplutils.cpp',
            ]
        ext = Extension('matplotlib._png', sources)
        pkg_config_setup_extension(
            ext, 'libpng',
            atleast_version='1.2',
            alt_exec=['libpng-config', '--ldflags'],
            default_libraries=(
                ['png', 'z'] if os.name == 'posix' else
                # libpng upstream names their lib libpng16.lib, not png.lib.
                [deplib('libpng16'), deplib('z')] if os.name == 'nt' else
                []
            ))
        add_numpy_flags(ext)
        return ext


class Qhull(SetupPackage):
    name = "qhull"

    def add_flags(self, ext):
        # Qhull doesn't distribute pkg-config info, so we have no way of
        # knowing whether a system install is recent enough.  Thus, always use
        # the vendored version.
        ext.include_dirs.insert(0, 'extern')
        ext.sources.extend(sorted(glob.glob('extern/libqhull/*.c')))
        if sysconfig.get_config_var('LIBM') == '-lm':
            ext.libraries.extend('m')


class TTConv(SetupPackage):
    name = "ttconv"

    def get_extension(self):
        sources = [
            'src/_ttconv.cpp',
            'extern/ttconv/pprdrv_tt.cpp',
            'extern/ttconv/pprdrv_tt2.cpp',
            'extern/ttconv/ttutil.cpp'
            ]
        ext = Extension('matplotlib.ttconv', sources)
        add_numpy_flags(ext)
        ext.include_dirs.insert(0, 'extern')
        return ext


class Path(SetupPackage):
    name = "path"

    def get_extension(self):
        sources = [
            'src/py_converters.cpp',
            'src/_path_wrapper.cpp'
            ]
        ext = Extension('matplotlib._path', sources)
        add_numpy_flags(ext)
        LibAgg().add_flags(ext)
        return ext


class Image(SetupPackage):
    name = "image"

    def get_extension(self):
        sources = [
            'src/_image.cpp',
            'src/mplutils.cpp',
            'src/_image_wrapper.cpp',
            'src/py_converters.cpp'
            ]
        ext = Extension('matplotlib._image', sources)
        add_numpy_flags(ext)
        LibAgg().add_flags(ext)

        return ext


class Contour(SetupPackage):
    name = "contour"

    def get_extension(self):
        sources = [
            "src/_contour.cpp",
            "src/_contour_wrapper.cpp",
            'src/py_converters.cpp',
            ]
        ext = Extension('matplotlib._contour', sources)
        add_numpy_flags(ext)
        LibAgg().add_flags(ext, add_sources=False)
        return ext


class QhullWrap(SetupPackage):
    name = "qhull_wrap"

    def get_extension(self):
        sources = ['src/qhull_wrap.c']
        ext = Extension('matplotlib._qhull', sources,
                        define_macros=[('MPL_DEVNULL', os.devnull)])
        add_numpy_flags(ext)
        Qhull().add_flags(ext)
        return ext


class Tri(SetupPackage):
    name = "tri"

    def get_extension(self):
        sources = [
            "src/tri/_tri.cpp",
            "src/tri/_tri_wrapper.cpp",
            "src/mplutils.cpp"
            ]
        ext = Extension('matplotlib._tri', sources)
        add_numpy_flags(ext)
        return ext


class BackendAgg(OptionalBackendPackage):
    name = "agg"
    force = True

    def get_extension(self):
        sources = [
            "src/mplutils.cpp",
            "src/py_converters.cpp",
            "src/_backend_agg.cpp",
            "src/_backend_agg_wrapper.cpp"
            ]
        ext = Extension('matplotlib.backends._backend_agg', sources)
        add_numpy_flags(ext)
        LibAgg().add_flags(ext)
        FreeType().add_flags(ext)
        return ext


class BackendTkAgg(OptionalBackendPackage):
    name = "tkagg"
    force = True

    def check(self):
        return "installing; run-time loading from Python Tcl/Tk"

    def get_extension(self):
        sources = [
            'src/_tkagg.cpp',
            'src/py_converters.cpp',
            ]

        ext = Extension('matplotlib.backends._tkagg', sources)
        self.add_flags(ext)
        add_numpy_flags(ext)
        LibAgg().add_flags(ext, add_sources=False)
        return ext

    def add_flags(self, ext):
        ext.include_dirs.insert(0, 'src')
        if sys.platform == 'win32':
            # psapi library needed for finding Tcl/Tk at run time.
            # user32 library needed for window manipulation functions.
            ext.libraries.extend(['psapi', 'user32'])
            ext.extra_link_args.extend(["-mwindows"])
        elif sys.platform == 'linux':
            ext.libraries.extend(['dl'])


class BackendMacOSX(OptionalBackendPackage):
    name = 'macosx'

    def check(self):
        if sys.platform != 'darwin':
            raise CheckFailed("Mac OS-X only")
        return super().check()

    def get_extension(self):
        sources = [
            'src/_macosx.m'
            ]
        ext = Extension('matplotlib.backends._macosx', sources)
        ext.extra_link_args.extend(['-framework', 'Cocoa'])
        if platform.python_implementation().lower() == 'pypy':
            ext.extra_compile_args.append('-DPYPY=1')
        return ext