Mini Shell

"""Enable wxPython to be used interactively in prompt_toolkit
"""

import sys
import signal
import time
from timeit import default_timer as clock
import wx


def ignore_keyboardinterrupts(func):
    """Decorator which causes KeyboardInterrupt exceptions to be ignored during
    execution of the decorated function.

    This is used by the inputhook functions to handle the event where the user
    presses CTRL+C while IPython is idle, and the inputhook loop is running. In
    this case, we want to ignore interrupts.
    """
    def wrapper(*args, **kwargs):
        try:
            func(*args, **kwargs)
        except KeyboardInterrupt:
            pass
    return wrapper


@ignore_keyboardinterrupts
def inputhook_wx1(context):
    """Run the wx event loop by processing pending events only.

    This approach seems to work, but its performance is not great as it
    relies on having PyOS_InputHook called regularly.
    """
    app = wx.GetApp()
    if app is not None:
        assert wx.Thread_IsMain()

        # Make a temporary event loop and process system events until
        # there are no more waiting, then allow idle events (which
        # will also deal with pending or posted wx events.)
        evtloop = wx.EventLoop()
        ea = wx.EventLoopActivator(evtloop)
        while evtloop.Pending():
            evtloop.Dispatch()
        app.ProcessIdle()
        del ea
    return 0


class EventLoopTimer(wx.Timer):

    def __init__(self, func):
        self.func = func
        wx.Timer.__init__(self)

    def Notify(self):
        self.func()


class EventLoopRunner(object):

    def Run(self, time, input_is_ready):
        self.input_is_ready = input_is_ready
        self.evtloop = wx.EventLoop()
        self.timer = EventLoopTimer(self.check_stdin)
        self.timer.Start(time)
        self.evtloop.Run()

    def check_stdin(self):
        if self.input_is_ready():
            self.timer.Stop()
            self.evtloop.Exit()


@ignore_keyboardinterrupts
def inputhook_wx2(context):
    """Run the wx event loop, polling for stdin.

    This version runs the wx eventloop for an undetermined amount of time,
    during which it periodically checks to see if anything is ready on
    stdin.  If anything is ready on stdin, the event loop exits.

    The argument to elr.Run controls how often the event loop looks at stdin.
    This determines the responsiveness at the keyboard.  A setting of 1000
    enables a user to type at most 1 char per second.  I have found that a
    setting of 10 gives good keyboard response.  We can shorten it further,
    but eventually performance would suffer from calling select/kbhit too
    often.
    """
    app = wx.GetApp()
    if app is not None:
        assert wx.Thread_IsMain()
        elr = EventLoopRunner()
        # As this time is made shorter, keyboard response improves, but idle
        # CPU load goes up.  10 ms seems like a good compromise.
        elr.Run(time=10,  # CHANGE time here to control polling interval
                input_is_ready=context.input_is_ready)
    return 0


@ignore_keyboardinterrupts
def inputhook_wx3(context):
    """Run the wx event loop by processing pending events only.

    This is like inputhook_wx1, but it keeps processing pending events
    until stdin is ready.  After processing all pending events, a call to
    time.sleep is inserted.  This is needed, otherwise, CPU usage is at 100%.
    This sleep time should be tuned though for best performance.
    """
    app = wx.GetApp()
    if app is not None:
        assert wx.Thread_IsMain()

        # The import of wx on Linux sets the handler for signal.SIGINT
        # to 0.  This is a bug in wx or gtk.  We fix by just setting it
        # back to the Python default.
        if not callable(signal.getsignal(signal.SIGINT)):
            signal.signal(signal.SIGINT, signal.default_int_handler)

        evtloop = wx.EventLoop()
        ea = wx.EventLoopActivator(evtloop)
        t = clock()
        while not context.input_is_ready():
            while evtloop.Pending():
                t = clock()
                evtloop.Dispatch()
            app.ProcessIdle()
            # We need to sleep at this point to keep the idle CPU load
            # low.  However, if sleep to long, GUI response is poor.  As
            # a compromise, we watch how often GUI events are being processed
            # and switch between a short and long sleep time.  Here are some
            # stats useful in helping to tune this.
            # time    CPU load
            # 0.001   13%
            # 0.005   3%
            # 0.01    1.5%
            # 0.05    0.5%
            used_time = clock() - t
            if used_time > 10.0:
                # print 'Sleep for 1 s'  # dbg
                time.sleep(1.0)
            elif used_time > 0.1:
                # Few GUI events coming in, so we can sleep longer
                # print 'Sleep for 0.05 s'  # dbg
                time.sleep(0.05)
            else:
                # Many GUI events coming in, so sleep only very little
                time.sleep(0.001)
        del ea
    return 0


@ignore_keyboardinterrupts
def inputhook_wxphoenix(context):
    """Run the wx event loop until the user provides more input.

    This input hook is suitable for use with wxPython >= 4 (a.k.a. Phoenix).

    It uses the same approach to that used in
    ipykernel.eventloops.loop_wx. The wx.MainLoop is executed, and a wx.Timer
    is used to periodically poll the context for input. As soon as input is
    ready, the wx.MainLoop is stopped.
    """

    app = wx.GetApp()

    if app is None:
        return

    if context.input_is_ready():
        return

    assert wx.IsMainThread()

    # Wx uses milliseconds
    poll_interval = 100

    # Use a wx.Timer to periodically check whether input is ready - as soon as
    # it is, we exit the main loop
    timer = wx.Timer()

    def poll(ev):
        if context.input_is_ready():
            timer.Stop()
            app.ExitMainLoop()

    timer.Start(poll_interval)
    timer.Bind(wx.EVT_TIMER, poll)

    # The import of wx on Linux sets the handler for signal.SIGINT to 0.  This
    # is a bug in wx or gtk.  We fix by just setting it back to the Python
    # default.
    if not callable(signal.getsignal(signal.SIGINT)):
        signal.signal(signal.SIGINT, signal.default_int_handler)

    # The SetExitOnFrameDelete call allows us to run the wx mainloop without
    # having a frame open.
    app.SetExitOnFrameDelete(False)
    app.MainLoop()


# Get the major wx version number to figure out what input hook we should use.
major_version = 3

try:
    major_version = int(wx.__version__[0])
except Exception:
    pass

# Use the phoenix hook on all platforms for wxpython >= 4
if major_version >= 4:
    inputhook = inputhook_wxphoenix
# On OSX, evtloop.Pending() always returns True, regardless of there being
# any events pending. As such we can't use implementations 1 or 3 of the
# inputhook as those depend on a pending/dispatch loop.
elif sys.platform == 'darwin':
    inputhook = inputhook_wx2
else:
    inputhook = inputhook_wx3