qutebrowser/qutebrowser/utils/debug.py

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

# Copyright 2014 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
#
# 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/>.

"""Utilities used for debugging."""

import re
import sys
import types
import functools

from PyQt5.QtCore import QEvent, QCoreApplication

from qutebrowser.utils import log, utils
from qutebrowser.commands import cmdutils
from qutebrowser.config import config, style


@cmdutils.register(debug=True)
def debug_crash(typ : ('exception', 'segfault') = 'exception'):
    """Crash for debugging purposes.

    Args:
        typ: either 'exception' or 'segfault'.

    Raises:
        raises Exception when typ is not segfault.
        segfaults when typ is (you don't say...)
    """
    if typ == 'segfault':
        # From python's Lib/test/crashers/bogus_code_obj.py
        co = types.CodeType(0, 0, 0, 0, 0, b'\x04\x71\x00\x00', (), (), (),
                            '', '', 1, b'')
        exec(co)  # pylint: disable=exec-used
        raise Exception("Segfault failed (wat.)")
    else:
        raise Exception("Forced crash")


@cmdutils.register(debug=True)
def debug_all_widgets():
    """Print a list of all widgets to debug log."""
    s = QCoreApplication.instance().get_all_widgets()
    log.misc.debug(s)


@cmdutils.register(debug=True)
def debug_all_objects():
    """Print a list of  all objects to the debug log."""
    s = QCoreApplication.instance().get_all_objects()
    log.misc.debug(s)


@cmdutils.register(debug=True)
def debug_cache_stats():
    """Print LRU cache stats."""
    config_info = config.instance().get.cache_info()
    style_info = style.get_stylesheet.cache_info()
    log.misc.debug('config: {}'.format(config_info))
    log.misc.debug('style: {}'.format(style_info))


def log_events(klass):
    """Class decorator to log Qt events."""
    old_event = klass.event

    @functools.wraps(old_event)
    def new_event(self, e, *args, **kwargs):
        """Wrapper for event() which logs events."""
        log.misc.debug("Event in {}: {}".format(klass.__name__,
                                                qenum_key(QEvent, e.type())))
        return old_event(self, e, *args, **kwargs)

    klass.event = new_event
    return klass


def trace_lines(do_trace):
    """Turn on/off printing each executed line.

    Args:
        do_trace: Whether to start tracing (True) or stop it (False).
    """
    def trace(frame, event, arg):
        """Trace function passed to sys.settrace.

        Return:
            Itself, so tracing continues.
        """
        if sys is not None:
            loc = '{}:{}'.format(frame.f_code.co_filename, frame.f_lineno)
            if arg is not None:
                arg = utils.compact_text(str(arg), 200)
            else:
                arg = ''
            print("{:11} {:80} {}".format(event, loc, arg), file=sys.stderr)
            return trace
        else:
            # When tracing while shutting down, it seems sys can be None
            # sometimes... if that's the case, we stop tracing.
            return None
    if do_trace:
        sys.settrace(trace)
    else:
        sys.settrace(None)


def qenum_key(base, value, add_base=False, klass=None):
    """Convert a Qt Enum value to its key as a string.

    Args:
        base: The object the enum is in, e.g. QFrame.
        value: The value to get.
        add_base: Whether the base should be added to the printed name.
        klass: The enum class the value belongs to.
               If None, the class will be auto-guessed.

    Return:
        The key associated with the value as a string if it could be found.
        The original value as a string if not.
    """
    if klass is None:
        klass = value.__class__
        if klass == int:
            raise TypeError("Can't guess enum class of an int!")
    try:
        idx = klass.staticMetaObject.indexOfEnumerator(klass.__name__)
    except AttributeError:
        idx = -1
    if idx != -1:
        ret = klass.staticMetaObject.enumerator(idx).valueToKey(value)
    else:
        for name, obj in vars(base).items():
            if isinstance(obj, klass) and obj == value:
                ret = name
                break
        else:
            ret = '0x{:04x}'.format(int(value))
    if add_base and hasattr(base, '__name__'):
        return '.'.join([base.__name__, ret])
    else:
        return ret


def qflags_key(base, value, add_base=False, klass=None):
    """Convert a Qt QFlags value to its keys as string.

    Note: Passing a combined value (such as Qt.AlignCenter) will get the names
    for the individual bits (e.g. Qt.AlignVCenter | Qt.AlignHCenter). FIXME

    Args:
        base: The object the flags are in, e.g. QtCore.Qt
        value: The value to get.
        add_base: Whether the base should be added to the printed names.
        klass: The flags class the value belongs to.
               If None, the class will be auto-guessed.

    Return:
        The keys associated with the flags as a '|' separated string if they
        could be found. Hex values as a string if not.
    """
    if klass is None:
        # We have to store klass here because it will be lost when iterating
        # over the bits.
        klass = value.__class__
        if klass == int:
            raise TypeError("Can't guess enum class of an int!")
    bits = []
    names = []
    mask = 0x01
    value = int(value)
    while mask < value:
        if value & mask:
            bits.append(mask)
        mask <<= 1
    for bit in bits:
        # We have to re-convert to an enum type here or we'll sometimes get an
        # empty string back.
        names.append(qenum_key(base, klass(bit), add_base))
    return '|'.join(names)


def signal_name(sig):
    """Get a cleaned up name of a signal.

    Args:
        sig: The pyqtSignal

    Return:
        The cleaned up signal name.
    """
    m = re.match(r'[0-9]+(.*)\(.*\)', sig.signal)
    return m.group(1)


def dbg_signal(sig, args):
    """Get a string representation of a signal for debugging.

    Args:
        sig: A pyqtSignal.
        args: The arguments as list of strings.

    Return:
        A human-readable string representation of signal/args.
    """
    argstr = ', '.join([utils.elide(str(a).replace('\n', ' '), 20)
                        for a in args])
    return '{}({})'.format(signal_name(sig), argstr)