Function inputhook_qt4

IPython/lib/inputhookqt4.py:78–159

PyOS_InputHook python hook for Qt4. Process pending Qt events and if there's no pending keyboard input, spend a short slice of time (50ms) running the Qt event loop. As a Python ctypes callback can't raise an exception, we catch the KeyboardInterrupt and tem

()

    # hooks (they both share the got_kbdint flag)

    def inputhook_qt4():
        """PyOS_InputHook python hook for Qt4.

        Process pending Qt events and if there's no pending keyboard
        input, spend a short slice of time (50ms) running the Qt event
        loop.

        As a Python ctypes callback can't raise an exception, we catch
        the KeyboardInterrupt and temporarily deactivate the hook,
        which will let a *second* CTRL+C be processed normally and go
        back to a clean prompt line.
        """
        try:
            allow_CTRL_C()
            app = QtCore.QCoreApplication.instance()
            if not app: # shouldn't happen, but safer if it happens anyway...
                return 0
            app.processEvents(QtCore.QEventLoop.AllEvents, 300)
            if not stdin_ready():
                # Generally a program would run QCoreApplication::exec()
                # from main() to enter and process the Qt event loop until
                # quit() or exit() is called and the program terminates.
                #
                # For our input hook integration, we need to repeatedly
                # enter and process the Qt event loop for only a short
                # amount of time (say 50ms) to ensure that Python stays
                # responsive to other user inputs.
                #
                # A naive approach would be to repeatedly call
                # QCoreApplication::exec(), using a timer to quit after a
                # short amount of time. Unfortunately, QCoreApplication
                # emits an aboutToQuit signal before stopping, which has
                # the undesirable effect of closing all modal windows.
                #
                # To work around this problem, we instead create a
                # QEventLoop and call QEventLoop::exec(). Other than
                # setting some state variables which do not seem to be
                # used anywhere, the only thing QCoreApplication adds is
                # the aboutToQuit signal which is precisely what we are
                # trying to avoid.
                timer = QtCore.QTimer()
                event_loop = QtCore.QEventLoop()
                timer.timeout.connect(event_loop.quit)
                while not stdin_ready():
                    timer.start(50)
                    event_loop.exec_()
                    timer.stop()
        except KeyboardInterrupt:
            global got_kbdint, sigint_timer

            ignore_CTRL_C()
            got_kbdint = True
            mgr.clear_inputhook()

            # This generates a second SIGINT so the user doesn't have to
            # press CTRL+C twice to get a clean prompt.
            #
            # Since we can't catch the resulting KeyboardInterrupt here