qutebrowser/qutebrowser/utils/earlyinit.py

# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:

# This file is part of qutebrowser.
#
# qutebrowser is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# qutebrowser is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.

"""Things which need to be done really early (e.g. before importing Qt).

At this point we can be sure we have all python 3.4 features available.
"""

import os
import sys
import faulthandler
import traceback
import signal
try:
    from tkinter import Tk, messagebox  # pylint: disable=import-error
except ImportError:
    Tk = None


def _missing_str(name, debian=None, arch=None, windows=None, pip=None):
    """Get an error string for missing packages.

    Args:
        name: The name of the package.
        debian: String to be displayed for Debian.
        arch: String to be displayed for Archlinux.
        windows: String to be displayed for Windows.
        pip: pypi package name.
    """
    blocks = ["Fatal error: {} is required to run qutebrowser but could "
              "not be imported! Maybe it's not installed?".format(name)]
    if debian is not None:
        lines = ["On Debian/Ubuntu:"]
        for line in debian.splitlines():
            lines.append('    ' + line)
        blocks.append('\n'.join(lines))
    if arch is not None:
        lines = ["On Archlinux:"]
        for line in arch.splitlines():
            lines.append('    ' + line)
        blocks.append('\n'.join(lines))
    if windows is not None:
        lines = ["On Windows:"]
        for line in windows.splitlines():
            lines.append('    ' + line)
        blocks.append('\n'.join(lines))
    lines = ["For other distributions:",
             "    Check your package manager for similiarly named packages."]
    if pip is not None:
        lines.append("    Or run  pip install {}  (using python3/pip3)".format(
            pip))
    blocks.append('\n'.join(lines))
    return '\n\n'.join(blocks)


def _die(message, exception=True):
    """Display an error message using Qt and quit.

    We import the imports here as we want to do other stuff before the imports.

    Args:
        message: The message to display.
        exception: Whether to print an exception with --debug.
    """
    from PyQt5.QtWidgets import QApplication, QMessageBox
    if '--debug' in sys.argv and exception:
        print(file=sys.stderr)
        traceback.print_exc()
    app = QApplication(sys.argv)
    msgbox = QMessageBox(QMessageBox.Critical, "qutebrowser: Fatal error!",
                         message)
    msgbox.resize(msgbox.sizeHint())
    msgbox.exec_()
    app.quit()
    sys.exit(1)


# Now we initialize the faulthandler as early as possible, so we theoretically
# could catch segfaults occuring later.
def init_faulthandler():
    """Enable faulthandler module if available.

    This print a nice traceback on segfauls.

    We use sys.__stderr__ instead of sys.stderr here so this will still work
    when sys.stderr got replaced, e.g. by "Python Tools for Visual Studio".
    """
    if sys.__stderr__ is None:
        # When run with pythonw.exe, sys.__stderr__ can be None:
        # https://docs.python.org/3/library/sys.html#sys.__stderr__
        # If we'd enable faulthandler in that case, we just get a weird
        # exception, so we don't enable faulthandler if we have no stdout.
        #
        # Later when we have our data dir available we re-enable faulthandler
        # to write to a file so we can display a crash to the user at the next
        # start.
        return
    faulthandler.enable(sys.__stderr__)
    if hasattr(faulthandler, 'register') and hasattr(signal, 'SIGUSR1'):
        # If available, we also want a traceback on SIGUSR1.
        faulthandler.register(signal.SIGUSR1)  # pylint: disable=no-member


# Now the faulthandler is enabled we fix the Qt harfbuzzing library, before
# importing QtWidgets.
def fix_harfbuzz(args):
    """Fix harfbuzz issues.

    This switches to the most stable harfbuzz font rendering engine available
    on the platform instead of using the system wide one.

    This fixes crashes on various sites.

    - On Qt 5.2 (and probably earlier) the new engine probably has more
      crashes and is also experimental.

      e.g. https://bugreports.qt-project.org/browse/QTBUG-36099

    - On Qt 5.3.0 there's a bug that affects a lot of websites:
      https://bugreports.qt-project.org/browse/QTBUG-39278
      So the new engine will be more stable.

    - On Qt 5.3.1 this bug is fixed and the old engine will be the more stable
      one again.

    IMPORTANT: This needs to be done before QWidgets is imported in any way!

    Args:
        args: The argparse namespace.
    """
    from qutebrowser.utils.log import init as logger
    from PyQt5.QtCore import qVersion
    if 'PyQt5.QtWidgets' in sys.modules:
        logger.warning("Harfbuzz fix attempted but QtWidgets is already "
                       "imported!")
    if sys.platform.startswith('linux') and args.harfbuzz == 'auto':
        if qVersion() == '5.3.0':
            logger.debug("Using new harfbuzz engine (auto)")
            os.environ['QT_HARFBUZZ'] = 'new'
        else:
            logger.debug("Using old harfbuzz engine (auto)")
            os.environ['QT_HARFBUZZ'] = 'old'
    elif args.harfbuzz in ('old', 'new'):
        # forced harfbuzz variant
        # FIXME looking at the Qt code, 'new' isn't a valid value, but leaving
        # it empty and using new yields different behaviour...
        logger.debug("Using {} harfbuzz engine (forced)".format(args.harfbuzz))
        os.environ['QT_HARFBUZZ'] = args.harfbuzz
    else:
        logger.debug("Using system harfbuzz engine")


# At this point we can safely import Qt stuff, but we can't be sure it's
# actually available.
# Here we check if QtCore is available, and if not, print a message to the
# console.
def check_pyqt_core():
    """Check if PyQt core is installed."""
    try:
        import PyQt5.QtCore  # pylint: disable=unused-variable
    except ImportError:
        text = _missing_str('PyQt5',
                            debian="apt-get install python3-pyqt5 "
                                   "python3-pyqt5.qtwebkit",
                            arch="pacman -S python-pyqt5 qt5-webkit\n"
                                 "or install the qutebrowser package from AUR",
                            windows="Use the installer by Riverbank computing "
                                    "or the standalone qutebrowser exe.\n"
                                    "http://www.riverbankcomputing.co.uk/"
                                    "software/pyqt/download5")
        if Tk:
            root = Tk()
            root.withdraw()
            messagebox.showerror("qutebrowser: Fatal error!", text)
        else:
            print(text, file=sys.stderr)
        if '--debug' in sys.argv:
            print(file=sys.stderr)
            traceback.print_exc()
        sys.exit(1)


# Now we can be sure QtCore is available, so we can print dialogs on errors, so
# people only using the GUI notice them as well.
def check_qt_version():
    """Check if the Qt version is recent enough."""
    import operator
    from PyQt5.QtCore import qVersion
    from qutebrowser.utils.qt import qt_version_check
    if qt_version_check('5.2.0', operator.lt):
        text = ("Fatal error: Qt and PyQt >= 5.2.0 are required, but {} is "
                "installed.".format(qVersion()))
        _die(text, exception=False)


def check_pyqt_webkit():
    """Check if PyQt WebKit is installed."""
    try:
        import PyQt5.QtWebKit  # pylint: disable=unused-variable
    except ImportError:
        text = _missing_str("QtWebKit",
                            debian="apt-get install python3-pyqt5.qtwebkit",
                            arch="pacman -S qt5-webkit")
        _die(text)


def check_pkg_resources():
    """Check if pkg_resources is installed."""
    try:
        import pkg_resources  # pylint: disable=unused-variable
    except ImportError:
        text = _missing_str("pkg_resources",
                            debian="apt-get install python3-pkg-resources",
                            arch="pacman -S python-setuptools",
                            windows="Run   python -m ensurepip  "
                                    "(python >= 3.4) or scripts/ez_setup.py.")
        _die(text)


def check_rfc6266():
    """Check if rfc6266 is installed."""
    try:
        import rfc6266  # pylint: disable=unused-variable
    except ImportError:
        text = _missing_str("rfc6266",
                            debian="No package available, try:\n"
                                   "pip3 install rfc6266",
                            arch="pacman -S python-rfc6266",
                            windows="pip install rfc6266    (using python3)",
                            pip="rfc6266")
        _die(text)