Source code for ewoksorange.bindings.qtapp

import gc
import sys
import time
import signal
import logging
from typing import Optional, Iterator
from contextlib import contextmanager
from AnyQt import QtCore
from AnyQt.QtWidgets import QApplication


_APP = None
_OLD_HANDLERS = None

logger = logging.getLogger(__name__)


def ensure_qtapp() -> Optional[QApplication]:
    """Create a Qt application without event loop when no application is running.
    Returns None when the application already exists."""
    global _APP
    if _APP is not None:
        return

    # GUI application
    _APP = get_qtapp()
    if _APP is not None:
        return

    # Install signal, exception and Qt message handlers
    _install_handlers()

    # Application without event loop (_APP.exec() is not called)
    _APP = QApplication([])
    return _APP


def _install_handlers() -> None:
    """Install signal, exception and Qt message handlers"""
    global _OLD_HANDLERS
    if _OLD_HANDLERS is not None:
        return
    # Allow termination with CTRL + C
    old_signal = signal.signal(signal.SIGINT, signal.SIG_DFL)

    # Redirect Qt logs
    old_qtmsg_handler = QtCore.qInstallMessageHandler(qt_message_handler)

    # Log unhandled exceptions, otherwise qFatal will be called
    old_ex_handler = sys.excepthook
    sys.excepthook = absorb_nonbase_exception

    _OLD_HANDLERS = old_signal, old_qtmsg_handler, old_ex_handler


def _remove_handlers() -> None:
    """Undo _install_handlers"""
    global _OLD_HANDLERS
    if _OLD_HANDLERS is None:
        return

    old_signal, old_qtmsg_handler, old_ex_handler = _OLD_HANDLERS

    signal.signal(signal.SIGINT, old_signal)

    QtCore.qInstallMessageHandler(old_qtmsg_handler)

    sys.excepthook = old_ex_handler

    _OLD_HANDLERS = None


def close_qtapp() -> None:
    """Close the Qt application created by ensure_qtapp"""
    global _APP
    if _APP is None:
        return
    _APP.processEvents()
    while gc.collect():
        _APP.processEvents()
    _APP.exit()
    _APP = None
    _remove_handlers()


@contextmanager
def qtapp_context() -> Iterator[Optional[QApplication]]:
    """Yields None when the Qt application already exists"""
    qtapp = ensure_qtapp()
    try:
        yield qtapp
    finally:
        if qtapp is not None:
            close_qtapp()


def get_qtapp() -> Optional[QApplication]:
    return QApplication.instance()


def process_qtapp_events() -> None:
    """Process all pending Qt events when a Qt event loop is running"""
    global _APP
    if _APP is None:
        return
    while _APP.hasPendingEvents():
        _APP.processEvents()


class QtEvent:
    """Event that also works for Qt applications with an event loop
    that needs to run manually"""

    def __init__(self) -> None:
        self.__flag = False

    def wait(self, timeout: Optional[float] = None) -> bool:
        """Processes events associated to the calling thread while waiting"""
        global _APP
        if timeout is not None:
            t0 = time.time()
        while not self.__flag:
            if _APP is None:
                time.sleep(0.1)
            else:
                _APP.processEvents(QtCore.QEventLoop.AllEvents, 100)
            if timeout is not None:
                if (time.time() - t0) > timeout:
                    return False
        return True

    def set(self) -> None:
        self.__flag = True

    def clear(self) -> None:
        self.__flag = False


def get_all_qtwidgets() -> list:
    app = get_qtapp()
    if app is None:
        return list()

    sapp = str(type(app))
    if "PyQt5" in sapp:
        from PyQt5.sip import ispycreated as createdByPython  # noqa
    elif "PySide2" in sapp:
        from PySide2.shiboken2 import createdByPython  # noqa
    else:
        raise RuntimeError(f"'{sapp}' not supported")

    return [widget for widget in app.allWidgets() if createdByPython(widget)]


def qt_message_handler(level, context, message) -> None:
    if level == QtCore.QtInfoMsg:
        log = logger.info
    elif level == QtCore.QtWarningMsg:
        log = logger.warning
    elif level == QtCore.QtCriticalMsg:
        log = logger.error
    elif level == QtCore.QtFatalMsg:
        log = logger.fatal
    else:
        log = logger.debug
    log(
        "line: %d, func: %s(), file: %s\nQT MESSAGE: %s\n",
        context.line,
        context.function,
        context.file,
        message,
    )


def absorb_nonbase_exception(exc_type, exc_value, exc_traceback) -> None:
    if not issubclass(exc_type, Exception):
        sys.__excepthook__(exc_type, exc_value, exc_traceback)
        return

    logger.error("Uncaught exception", exc_info=(exc_type, exc_value, exc_traceback))