omz:forum

TPO

@mikael you could try FuzzyFinder in 10 lines of Python

Cheers,

TPO

@Jhonmicky, I have had the exact same need for an app I am currently developping.

You can use Desktop.py below as follows:

Run the module on the PC
On the iPhone :

from Desktop import announce_service

# Will launch Firefox on the Desktop, and open 'your_url'
announce_service(your_url, True)
...
# (Optional) Will close the Firefox window
announce_service(your_url, False)

Lots of things can be configured, please see in the source code. This module was developped for a specific application (MyDB, you will see it mentionned several times in the source), not as a general purpose module, you may have to tweak it a bit to suit your needs.

Note on implementation : what started out as a simple UDP broadcast function ended up as a full protocol with a fallback against routers that filter out UDP broadcast packets, and fences against lost or delayed packets, WiFi networks that are slow to authenticate, etc., as I tried it out in various environments (a tame Internet Box at home, enterprise LAN, hotel LAN, etc.)

This is still work in progress.

Hope this helps.

""" Desktop companion for MyDB Web UI.

There are two components to this module:
- service_daemon() runs on the desktop. It will automatically open a browser
  window when the user activates desktop mode on the iPhone, and close the
  browser window when the user exits desktop mode. This is done by listening
  for MyDB Web UI service announcements.
- announce_service() is used by Web_UI.py, to announce that MyDB's Web UI
  service is available / unavailable.

Revision history:
22-Jul-2019 TPO - Created this module
25-Jul-2019 TPO - Initial release """

import json
import os
import socket
import subprocess
import time
import threading

# When the following variable is set to True, both service_daemon() and
# announce_service() will print debug information on stdout. 
DEBUG = True

# Change the following 2 variables if using another browser than Firefox:
START_BROWSER = [(r'"C:\Program Files (x86)\Mozilla Firefox\Firefox.exe" '
                  r'-new-window {ip}/'),
                 (r'"C:\Program Files\Mozilla Firefox\Firefox.exe" '
                  r'-new-window {ip}/')]
STOP_BROWSER = r'TASKKILL /IM firefox.exe /FI "WINDOWTITLE eq MyDB*"'


ANNOUNCE_PORT = 50000
ACK_PORT = 50001
MAGIC = "XXMYDBXX"

ANNOUNCE_COUNTER = 0


def debug(message: str) -> None:
    global DEBUG
    if DEBUG:
        print(message)


def announce_service(ip: str, available: bool) -> bool:
    """ Announce that MyDB's Web UI service is available / unavailable.

    Broadcast the status of the MyDB Web UI service, so that the desktop
    daemon can open a browser window when the user activates desktop mode on
    the iPhone, and close the browser window when the user exits desktop mode.

    Arguments:
    - ip: string containing our IP address.
    - available: if True, announce that the service is now available. If False,
      announce that the service is now unavailable.

    Returns: True if the announcement has been received and ackowledged by the
    desktop daemon, False otherwise.

    Two broadcast modes are tried:
    - UDP broadcast is tried first (code is courtesy of goncalopp,
      https://stackoverflow.com/a/21090815)
    - If UDP broadcast fails, as can happen on LANs where broadcasting packets
      are filtered by the routers (think airport or hotel LAN), a brute force
      method is tried, by sending the announcement packet to 254 IP adresses,
      using values 1 - 255 for byte 4 of our own IP address (should actually
      use subnet mask, but this is a quick and dirty kludge !)

    TODO: document ACK mechanism + counter and session id """

    def do_brute_force_broadcast(s: socket.socket,
                                 ip: str,
                                 port: int,
                                 data: bytes) -> None:
        ip_bytes_1_to_3 = ip[:ip.rfind('.')] + '.'
        for i in range(1, 255):
            print(i, sep=" ")
            s.sendto(data, (ip_bytes_1_to_3 + str(i), port))
        print(".")

    global ACK_PORT, ANNOUNCE_PORT, MAGIC, ANNOUNCE_COUNTER
    SOCKET_TIMEOUT = 0.3
    data = json.dumps({'magic': MAGIC,
                       'counter': ANNOUNCE_COUNTER,
                       'service available': available,
                       'IP': ip,
                       'Session id': time.time()}).encode('utf-8')
    snd = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    snd.bind(('', ANNOUNCE_PORT))
    rcv = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    rcv.bind(('', ACK_PORT))
    rcv.settimeout(SOCKET_TIMEOUT)
    ack = False
    debug(f"Counter = {ANNOUNCE_COUNTER}, announcing service is "
          f"{'ON' if available else 'OFF'}")
    for brute_force, retries in ((False, 3), (True, 8)):
        debug(f"  Trying {'Brute force' if brute_force else 'UDP'} broadcast")
        snd.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, not brute_force)
        for retry in range(retries):
            debug(f"    Retry # {retry}")
            if brute_force:
                brute_force_broadcast_thread = threading.Thread(
                    target=do_brute_force_broadcast,
                    args=(snd, ip, ANNOUNCE_PORT, data))
                brute_force_broadcast_thread.start()
            else:
                snd.sendto(data, ('<broadcast>', ANNOUNCE_PORT))
            while 1:
                try:
                    data_bytes, addr = rcv.recvfrom(1024)
                except socket.timeout:
                    debug("      Socket time out, going for next retry")
                    break
                debug(f"      Received {data_bytes}")
                try:
                    data = json.loads(data_bytes.decode('utf-8'))
                except json.JSONDecodeError:
                    debug("      Invalid JSON, ignoring")
                    continue
                if (isinstance(data, dict)
                        and data.get('magic') == MAGIC
                        and data.get('counter') == ANNOUNCE_COUNTER
                        and data.get('IP') == ip):
                    debug("      ACK received")
                    ack = True
                    break
                print("      Invalid ACK, ignoring")
            if ack:
                break
        if brute_force:
            # Need to wait for broadcast_thread to be done before we proceed
            # to close the snd socket, or do_brute_force_broadcast() will fail
            # with "Errno 9: Bad file descriptor".
            brute_force_broadcast_thread.join()
        if ack:
            break
    if not ack:
        debug("  Both UDP and brute force broadcast methods failed, giving up")
    snd.close()
    rcv.close()
    ANNOUNCE_COUNTER += 1
    return ack


def service_daemon():
    """ Automatically open / close web browser on desktop.

    service_daemon() runs on the desktop. It will automatically open a browser
    window when the user activates desktop mode on the iPhone, and close the
    browser window when the user exits desktop mode. This is done by listening
    for MyDB Web UI service announcements. """

    global ACK_PORT, ANNOUNCE_PORT, MAGIC

    # Keep track of the counter value for last annoucement packet processed, in
    # order to ignore retry packets sent by announce_service(), which all have
    # the same counter value.
    last_counter = -1

    # Web_UI sessions all start with a counter value of 0, so we need to keep
    # track of Web_UI sessions and reset last_counter every time a new session
    # is started (i.e. when the user activates desktop mode on the iPhone)
    current_session_id = -1

    rcv = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    rcv.bind(('', ANNOUNCE_PORT))
    snd = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    snd.bind(('', ACK_PORT))
    debug(f"Listening on port {ANNOUNCE_PORT}")
    while 1:
        data_bytes, addr = rcv.recvfrom(1024)
        debug(f"Received packet from {addr}:\n    '{data_bytes}'")
        try:
            data = json.loads(data_bytes.decode('utf-8'))
        except json.JSONDecodeError:
            debug("    Invalid JSON, ignoring")
            continue
        if (isinstance(data, dict)
                and data.get('magic') == MAGIC
                and 'counter' in data
                and 'IP' in data
                and 'service available' in data
                and 'Session id' in data):
            if (data['Session id'] == current_session_id
                    and data['counter'] <= last_counter):
                debug(f"    Ignoring MyDB announcement for counter = "
                      f"{data['counter']}, already processed")
                continue
            current_session_id = data['Session id']
            last_counter = data['counter']
            debug(f"    MyDB announcement: IP = {data['IP']}, "
                  f"service {'ON' if data['service available'] else 'OFF'}, "
                  f"counter = {data['counter']}")
            ack = json.dumps({'magic': MAGIC,
                              'counter': data['counter'],
                              'IP': data['IP']}).encode('utf-8')
            snd.sendto(ack, (data['IP'], ACK_PORT))
            debug(f"    ACK sent back to {data['IP']}:{ACK_PORT}")
            if data['service available']:
                debug("    Launching browser")
                for start_browser in START_BROWSER:
                    try:
                        subprocess.Popen(start_browser.format(ip=data['IP']))
                    except FileNotFoundError:
                        continue
                    break
            else:
                debug("    Closing browser")
                os.system(STOP_BROWSER)
        else:
            debug("    Not a MyDB announcement, ignoring")


if __name__ == '__main__':
    service_daemon()

TPO

@shinyformica, I have the same issue and have come up with a solution based on a simple protocol. When applications follow the protocol, they will not "pile up on top of one another" when launched from the iOS home screen:

When an app is already active in Pythonista and it is launched again with its home screen shortcut, the new instance of the app detects the situation and exits, leaving the already active instance of the app on screen.
When an app is launched from its home screen shortcut and a previous app is already active in Pythonista, the previous app will be notified that it should terminate, its main UI view will be closed, and the new app will be launched.

Protocol

An application should create an instance of class AppSingleLaunch, and use it to test if the application is already active, using the is_active() method. If yes, the application should simply exit. If not, the application should declare its main UI view, using the will_present() method, and present the view. Here is an example:
```
 import app_single_launch

 app = AppSingleLaunch("MyApp")
 if not app.is_active():
     view = MyAppView(app)
     app.will_present(view)
     view.present()
```

An application should make a call to the AppSingleLaunch.will_close() method, from the will_close() method of its main UI view:

 class MyAppView(ui.View):

     def __init__(self, app):
         self.app = app

     def will_close(self):
       self.app.will_close()

Demo

Save the code for app_single_launch.py and the two demo apps in the same directory.

Define home screen shortcuts for the two demo apps.

Launch demo app 1 using its home screen shortcut, type some text in the text field, then relaunch the app using its home screen shortcut : the text typed previously is still showing, meaning we are using the first launched instance, not the second one. Closing the app brings us back to the Pythonista IDE, not to previously piled up instances of the app.

Launch demo app 1 using its home screen shortcut, then Launch demo app 2 using its home screen shortcut, then close it : the Pythonista IDE shows, not a piled up instance of demo app 1.

Et voilà !

app_single_launch.py

""" Ensure a Pythonista script can only be launched once from the iOS home screen.

This module provides a solution to the problem stated by shinyformica, which I
have also encountered (https://forum.omz-software.com/topic/5440/prevent-
duplicate-launch-from-shortcut):
    "Is there a good, canonical way to prevent a script from launching again if
    there is already an instance running? Specifically, I want to prevent the
    scenario where a user launches the script from the home screen via an app
    shortcut, then goes back to the home screen and launches it again.""

The solution is based on a simple protocol, which applications need to adhere
to. When this is the case, applications will not "pile up on top of one another"
when launched from the iOS home screen:
- When an app is already active in Pythonista and it is launched again with its
  home screen shortcut, the new instance of the app detects the situation and
  exits, leaving the already active instance of the app on screen.
- When an app is launched from its home screen shortcut and a previous app is
  already active in Pythonista, the previous app will be notified that it
  should terminate, its main UI view will be closed, and the new app will be
  launched.

Protocol:
1) An application should create an instance of class AppSingleLaunch, and use
   it to test if the application is already active, using the is_active()
   method. If yes, the application should simply exit. If not, the application
   should declare its main UI view, using the will_present() method, and
   present the view. Here is an example:

        import app_single_launch

        app = AppSingleLaunch("MyApp")
        if not app.is_active():
            view = MyAppView(app)
            app.will_present(view)
            view.present()

2) An application should make a call to the AppSingleLaunch.will_close()
   method, from the will_close() method of its main UI view:

        class MyAppView(ui.View):

            def __init__(self, app):
                self.app = app

            def will_close(self):
              self.app.will_close()

Implementation: in order to achieve the desired result, we need to remember the
last application launched according to the protocol, to determine if it is
still active, and, if it is, to close it. This is achieved by storing into a
lock file some information about the last application launched:
- Its name, as passed to single_launch.launching()
- The id of the ui.View instance for its main view, as passed to single_launch.
  launching(). This is later used to determine if the view is still on screen
  (when an object is still associated with the id), and to close the app's view.
  After several tests, it turns out we must use an ui.View object for this
  purpose, as they seem to persist better than other objects after the cleanup
  pykit-preflight.py does when an app is launched from the home screen.
The location of the lock file is defined by global variable LOCK_PATH. The
default location is in the 'site-packages' directory.

Known issue:
- When an app is on screen, then launched again from its home screen shortcut,
  some issues may happen with inline import statements (rare, would need to be
  qualified further).

26-Feb-2019 TPO - Created this module
28-Feb-2019 TPO - Initial release
 3-Mar-2019 TPO - Wrapped the code into the AppSingleLaunch class """


import gc
import json
from pathlib import Path
import time
from typing import Any

import ui


__all__ = [
    'AppSingleLaunch',
]


DEBUG = False
LOCK_PATH = '~/Documents/site-packages/single_launch.lock'


def _object_for_id(id_: int) -> Any:
    """ Return an object, given its id. """

    # Do a complete garbage collect, to avoid false positives in case the
    # object was still in use recently. In the context of AppSingleLaunch,
    # this would happen if an app was closed, then launched again immediately.
    gc.collect()
    for obj in gc.get_objects():
        if id(obj) == id_:
            return obj
    return None


class AppSingleLaunch:
    """ Wrapper class for all module functionnality. """

    def __init__(self, app: str):
        """ Initialize an AppSingleLaunch instance.

        Arguments:
        - app: application name, which should be unique (but this is not
        enforced). """
        self.app = app

    def is_active(self) -> bool:
        """ Test if the application is already active.

        Returns:
        - True if the application is already running, in which case the caller
          should do nothing and exit.
        - False if the application is not already running, in which case the
          caller should launch the application in a normal way, and declare its
          main view by calling the will_present() method."""
        if DEBUG:
            print(f"is_active(), app = {self.app}")
        lock_path = Path(LOCK_PATH).expanduser()
        if lock_path.exists():
            with open(lock_path) as lock_file:
                (lock_app, lock_view_id) = tuple(json.load(lock_file))
            lock_view = _object_for_id(lock_view_id)
            if DEBUG:
                print("- Lock file =", lock_app, lock_view_id,
                      "valid" if lock_view else "invalid")
            if lock_app == self.app and lock_view:
                if DEBUG:
                    print(f"- App {self.app} already active")
                return True
        if DEBUG:
            print(f"- App {self.app} not active")
        return False

    def will_present(self, view: ui.View) -> None:
        """ Declare that the application is about to present its main view.

        Arguments:
        - view: ui.View instance for the app's main view. """
        if DEBUG:
            print(f"will_present({id(view)}), app = {self.app}")
        lock_path = Path(LOCK_PATH).expanduser()
        if lock_path.exists():
            with open(lock_path) as lock_file:
                (lock_app, lock_view_id) = tuple(json.load(lock_file))
            lock_view = _object_for_id(lock_view_id)
            if DEBUG:
                print("- Lock file =", lock_app, lock_view_id,
                      "valid" if lock_view else "invalid")
            if lock_app == self.app and lock_view:
                raise ValueError(f"App {self.app} is already active, cannot "
                                 f"call will_present() against it.")
            else:
                if lock_view and isinstance(lock_view, ui.View):
                    if DEBUG:
                        print(f"- Closing app {lock_app}")
                    lock_view.close()
                    time.sleep(1)  # Required for view to close properly
                # else: lock is a leftover from a previous Pythonista session
                #       and can be safely ignored.
        with open(lock_path, 'w') as lock_file:
            json.dump([self.app, id(view)], lock_file)
        if DEBUG:
            print(f"- Launching app {self.app}\n- Lock file =", self.app, id(view))

    def will_close(self) -> None:
        """ Declare that the application is about to close its main view. """
        lock_path = Path(LOCK_PATH).expanduser()
        if lock_path.exists():
            with open(lock_path) as lock_file:
                (lock_app, lock_view_id) = tuple(json.load(lock_file))
            if lock_app != self.app:
                raise ValueError(f"App {self.app} if not active, "
                                 f"{lock_app} is active")
            lock_path.unlink()

single_launch_demo1.py

""" app_single_launch demo script #1. """
from app_single_launch import AppSingleLaunch
import ui


class MainView(ui.View):
    def __init__(self, app: AppSingleLaunch):
        self.app = app
        self.name = "Demo app 1"
        self.flex = 'WH'
        self.background_color = 'white'
        self.add_subview(ui.TextField(
            width=200,
            height=30,
            placeholder="Type some text"))

    def will_close(self) -> None:
        self.app.will_close()


if __name__ == '__main__':
    app = AppSingleLaunch("Demo app 1")
    if not app.is_active():
        view = MainView(app)
        app.will_present(view)
        view.present()

single_launch_demo2.py

""" app_single_launch demo script #2. """
from app_single_launch import AppSingleLaunch
import ui


class MainView(ui.View):
    def __init__(self, app: AppSingleLaunch):
        self.app = app
        self.name = "Demo app 2"
        self.flex = 'WH'
        self.background_color = 'white'
        self.add_subview(ui.TextField(
            width=200,
            height=30,
            placeholder="Type some text"))

    def will_close(self) -> None:
        self.app.will_close()


if __name__ == '__main__':
    app = AppSingleLaunch("Demo app 2")
    if not app.is_active():
        view = MainView(app)
        app.will_present(view)
        view.present()

TPO

I have packaged cvp's solution into a module, which works like a charm, thanks a lot cvp ! (I use it for a newsreader).

I have come across two limitations, though:

reader_view() cannot be used if 'uiview' has a NavigationView, or if any view presented below it has a NavigationView (even if the view has no relationship with 'uiview' - very strange)
No resizing is performed when the reader view changes orientation

I am not very proficient with objc, would anyone know how to improve this ?

""" Modal view which displays a web page in reader mode.

Based on cvp's code:
https://forum.omz-software.com/topic/5392/webview-and-reader-mode/18

When run as a script, the module shows a small demo application.

Implementation note:

    Transmitting the callback function from reader_view() to safariView-
    ControllerDidFinish_() turns out to be trickier than expected, especially
    when combining reader_view.py with app_single_launch.py.

    In this case, when the user launches the same app a second time, a new
    'safari_view_controler' instance seems to be created automagically. We
    therefore cannot store the callback function as one of the 'safari_view_
    controler's properties, since the instance created by reader_view() is
    silently replaced by a new instance when the app is relaunched, and
    ControllerDidFinish_() will receive the new instance, not the old one.

    In the end, the simplest solution works, i.e. storing the callback in a
    global. This does of course come with theoretical limitations: an applica-
    tion should not make a second call to reader_view() until the reader view
    displayed by the first call has been closed. This should not be too much of
    an issue, as I really cannot imagine a practical use case for doing this. I
    have included a simple protection against this edge case anyway.

Revision history:
 6-Fev-2019 TPO - Initial release
28-Fev-2019 TPO - Added the 'enter_reader_mode' argument to reader_view()
 7-Mar-2019 TPO - reader_view() now works when used with app_single_launch.py """


from typing import Callable, Optional

from objc_util import create_objc_class, nsurl, ObjCClass, ObjCInstance
import ui


__all__ = [
    'reader_view',
]


Callback = Callable[[], None]
__CALLBACK: Optional[Callback]
__READER_VIEW_DISPLAYED = False


def safariViewControllerDidFinish_(_self, _cmd, _controller):
    global __CALLBACK, __READER_VIEW_DISPLAYED
    if __CALLBACK:
        __CALLBACK()
    __READER_VIEW_DISPLAYED = False


def reader_view(url: str,
                uiview: ui.View,
                callback: Optional[Callback] = None,
                enter_reader_mode: bool = True) -> None:
    """ Modal view which displays a web page in reader mode.

    Arguments:
    - url: of the web page to be displayed. The only URL schemes allowed are
      http and https.  Any other URL scheme will raise an Objective-C exception
      and cause Pythonista to be terminated.
    - uiview: ui.View instance on which the web view is to be displayed. Note
      that reader_view() does not work if this is an instance of ui.Navigation-
      View.
    - callback: function of no argument, which is called when the user closes
      the view.
    - enter_reader_mode: if true and if reader mode is available, it will be
      entered automatically; if false, the user will have to tap the reader
      mode icon to enter reader mode (when available). """
    global __CALLBACK, __READER_VIEW_DISPLAYED
    if __READER_VIEW_DISPLAYED:
        raise ValueError("reader_view() already in use")
    __READER_VIEW_DISPLAYED = True
    __CALLBACK = callback

    MySFSafariViewControllerDelegate = create_objc_class(
        'MySFSafariViewControllerDelegate',
        methods=[safariViewControllerDidFinish_],
        protocols=['SFSafariViewControllerDelegate'])
    delegate = MySFSafariViewControllerDelegate.alloc().init()
    safari_view_controler_conf = (
        ObjCClass('SFSafariViewControllerConfiguration').alloc().init())
    safari_view_controler_conf.setEntersReaderIfAvailable_(enter_reader_mode)
    safari_view_controler = ObjCClass('SFSafariViewController').alloc() \
        .initWithURL_configuration_(nsurl(url), safari_view_controler_conf)
    safari_view_controler.delegate = delegate
    safari_view_controler.setModalPresentationStyle_(3)  # 3 = currentContext
    vc = ObjCClass('SUIViewController').viewControllerForView_(ObjCInstance(uiview))
    vc.presentViewController_animated_completion_(safari_view_controler, True, None)


if __name__ == '__main__':
    from datetime import datetime

    def done():
        print("After user has closed reader view", datetime.now())

    def test(sender):
        print("Before call to reader_view()", datetime.now())
        reader_view(url=url, uiview=view, callback=done)

    url = 'http://www.nytimes.com/2019/01/29/climate/global-warming-extreme-weather.html'
    view = ui.View(
        flex='WH',
        background_color='white',
        name='reader_view demo',
        right_button_items=[ui.ButtonItem(title='test', action=test)])
    view.present()

TPO

@mikael you could try FuzzyFinder in 10 lines of Python

Cheers,

TPO

@nfmusician there you go : https://github.com/TPO-POMGOM/Pythonista-utilities

(I currently lack time to migrate to Github other utilities and modules I have developped for Pythonista, will do it as soon as time allows)

TPO

@Jhonmicky, can you be more precise on your use case ?

More specifically, does your Windows 10 PC have a fixed IP address ? If so, the method proposed by @bennr01 should work (and would be simpler). If your PC does not have a fixed IP address, then you need to establish a protocol between your iOS device and your windows PC, so that they can exchange IP addresses (and this is where the module I posted earlier would come in handy).

TPO

@Jhonmicky, I have had the exact same need for an app I am currently developping.

You can use Desktop.py below as follows:

Run the module on the PC
On the iPhone :

from Desktop import announce_service

# Will launch Firefox on the Desktop, and open 'your_url'
announce_service(your_url, True)
...
# (Optional) Will close the Firefox window
announce_service(your_url, False)

Lots of things can be configured, please see in the source code. This module was developped for a specific application (MyDB, you will see it mentionned several times in the source), not as a general purpose module, you may have to tweak it a bit to suit your needs.

Note on implementation : what started out as a simple UDP broadcast function ended up as a full protocol with a fallback against routers that filter out UDP broadcast packets, and fences against lost or delayed packets, WiFi networks that are slow to authenticate, etc., as I tried it out in various environments (a tame Internet Box at home, enterprise LAN, hotel LAN, etc.)

This is still work in progress.

Hope this helps.

""" Desktop companion for MyDB Web UI.

There are two components to this module:
- service_daemon() runs on the desktop. It will automatically open a browser
  window when the user activates desktop mode on the iPhone, and close the
  browser window when the user exits desktop mode. This is done by listening
  for MyDB Web UI service announcements.
- announce_service() is used by Web_UI.py, to announce that MyDB's Web UI
  service is available / unavailable.

Revision history:
22-Jul-2019 TPO - Created this module
25-Jul-2019 TPO - Initial release """

import json
import os
import socket
import subprocess
import time
import threading

# When the following variable is set to True, both service_daemon() and
# announce_service() will print debug information on stdout. 
DEBUG = True

# Change the following 2 variables if using another browser than Firefox:
START_BROWSER = [(r'"C:\Program Files (x86)\Mozilla Firefox\Firefox.exe" '
                  r'-new-window {ip}/'),
                 (r'"C:\Program Files\Mozilla Firefox\Firefox.exe" '
                  r'-new-window {ip}/')]
STOP_BROWSER = r'TASKKILL /IM firefox.exe /FI "WINDOWTITLE eq MyDB*"'


ANNOUNCE_PORT = 50000
ACK_PORT = 50001
MAGIC = "XXMYDBXX"

ANNOUNCE_COUNTER = 0


def debug(message: str) -> None:
    global DEBUG
    if DEBUG:
        print(message)


def announce_service(ip: str, available: bool) -> bool:
    """ Announce that MyDB's Web UI service is available / unavailable.

    Broadcast the status of the MyDB Web UI service, so that the desktop
    daemon can open a browser window when the user activates desktop mode on
    the iPhone, and close the browser window when the user exits desktop mode.

    Arguments:
    - ip: string containing our IP address.
    - available: if True, announce that the service is now available. If False,
      announce that the service is now unavailable.

    Returns: True if the announcement has been received and ackowledged by the
    desktop daemon, False otherwise.

    Two broadcast modes are tried:
    - UDP broadcast is tried first (code is courtesy of goncalopp,
      https://stackoverflow.com/a/21090815)
    - If UDP broadcast fails, as can happen on LANs where broadcasting packets
      are filtered by the routers (think airport or hotel LAN), a brute force
      method is tried, by sending the announcement packet to 254 IP adresses,
      using values 1 - 255 for byte 4 of our own IP address (should actually
      use subnet mask, but this is a quick and dirty kludge !)

    TODO: document ACK mechanism + counter and session id """

    def do_brute_force_broadcast(s: socket.socket,
                                 ip: str,
                                 port: int,
                                 data: bytes) -> None:
        ip_bytes_1_to_3 = ip[:ip.rfind('.')] + '.'
        for i in range(1, 255):
            print(i, sep=" ")
            s.sendto(data, (ip_bytes_1_to_3 + str(i), port))
        print(".")

    global ACK_PORT, ANNOUNCE_PORT, MAGIC, ANNOUNCE_COUNTER
    SOCKET_TIMEOUT = 0.3
    data = json.dumps({'magic': MAGIC,
                       'counter': ANNOUNCE_COUNTER,
                       'service available': available,
                       'IP': ip,
                       'Session id': time.time()}).encode('utf-8')
    snd = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    snd.bind(('', ANNOUNCE_PORT))
    rcv = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    rcv.bind(('', ACK_PORT))
    rcv.settimeout(SOCKET_TIMEOUT)
    ack = False
    debug(f"Counter = {ANNOUNCE_COUNTER}, announcing service is "
          f"{'ON' if available else 'OFF'}")
    for brute_force, retries in ((False, 3), (True, 8)):
        debug(f"  Trying {'Brute force' if brute_force else 'UDP'} broadcast")
        snd.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, not brute_force)
        for retry in range(retries):
            debug(f"    Retry # {retry}")
            if brute_force:
                brute_force_broadcast_thread = threading.Thread(
                    target=do_brute_force_broadcast,
                    args=(snd, ip, ANNOUNCE_PORT, data))
                brute_force_broadcast_thread.start()
            else:
                snd.sendto(data, ('<broadcast>', ANNOUNCE_PORT))
            while 1:
                try:
                    data_bytes, addr = rcv.recvfrom(1024)
                except socket.timeout:
                    debug("      Socket time out, going for next retry")
                    break
                debug(f"      Received {data_bytes}")
                try:
                    data = json.loads(data_bytes.decode('utf-8'))
                except json.JSONDecodeError:
                    debug("      Invalid JSON, ignoring")
                    continue
                if (isinstance(data, dict)
                        and data.get('magic') == MAGIC
                        and data.get('counter') == ANNOUNCE_COUNTER
                        and data.get('IP') == ip):
                    debug("      ACK received")
                    ack = True
                    break
                print("      Invalid ACK, ignoring")
            if ack:
                break
        if brute_force:
            # Need to wait for broadcast_thread to be done before we proceed
            # to close the snd socket, or do_brute_force_broadcast() will fail
            # with "Errno 9: Bad file descriptor".
            brute_force_broadcast_thread.join()
        if ack:
            break
    if not ack:
        debug("  Both UDP and brute force broadcast methods failed, giving up")
    snd.close()
    rcv.close()
    ANNOUNCE_COUNTER += 1
    return ack


def service_daemon():
    """ Automatically open / close web browser on desktop.

    service_daemon() runs on the desktop. It will automatically open a browser
    window when the user activates desktop mode on the iPhone, and close the
    browser window when the user exits desktop mode. This is done by listening
    for MyDB Web UI service announcements. """

    global ACK_PORT, ANNOUNCE_PORT, MAGIC

    # Keep track of the counter value for last annoucement packet processed, in
    # order to ignore retry packets sent by announce_service(), which all have
    # the same counter value.
    last_counter = -1

    # Web_UI sessions all start with a counter value of 0, so we need to keep
    # track of Web_UI sessions and reset last_counter every time a new session
    # is started (i.e. when the user activates desktop mode on the iPhone)
    current_session_id = -1

    rcv = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    rcv.bind(('', ANNOUNCE_PORT))
    snd = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    snd.bind(('', ACK_PORT))
    debug(f"Listening on port {ANNOUNCE_PORT}")
    while 1:
        data_bytes, addr = rcv.recvfrom(1024)
        debug(f"Received packet from {addr}:\n    '{data_bytes}'")
        try:
            data = json.loads(data_bytes.decode('utf-8'))
        except json.JSONDecodeError:
            debug("    Invalid JSON, ignoring")
            continue
        if (isinstance(data, dict)
                and data.get('magic') == MAGIC
                and 'counter' in data
                and 'IP' in data
                and 'service available' in data
                and 'Session id' in data):
            if (data['Session id'] == current_session_id
                    and data['counter'] <= last_counter):
                debug(f"    Ignoring MyDB announcement for counter = "
                      f"{data['counter']}, already processed")
                continue
            current_session_id = data['Session id']
            last_counter = data['counter']
            debug(f"    MyDB announcement: IP = {data['IP']}, "
                  f"service {'ON' if data['service available'] else 'OFF'}, "
                  f"counter = {data['counter']}")
            ack = json.dumps({'magic': MAGIC,
                              'counter': data['counter'],
                              'IP': data['IP']}).encode('utf-8')
            snd.sendto(ack, (data['IP'], ACK_PORT))
            debug(f"    ACK sent back to {data['IP']}:{ACK_PORT}")
            if data['service available']:
                debug("    Launching browser")
                for start_browser in START_BROWSER:
                    try:
                        subprocess.Popen(start_browser.format(ip=data['IP']))
                    except FileNotFoundError:
                        continue
                    break
            else:
                debug("    Closing browser")
                os.system(STOP_BROWSER)
        else:
            debug("    Not a MyDB announcement, ignoring")


if __name__ == '__main__':
    service_daemon()

TPO

@shinyformica, I have the same issue and have come up with a solution based on a simple protocol. When applications follow the protocol, they will not "pile up on top of one another" when launched from the iOS home screen:

When an app is already active in Pythonista and it is launched again with its home screen shortcut, the new instance of the app detects the situation and exits, leaving the already active instance of the app on screen.
When an app is launched from its home screen shortcut and a previous app is already active in Pythonista, the previous app will be notified that it should terminate, its main UI view will be closed, and the new app will be launched.

Protocol

An application should create an instance of class AppSingleLaunch, and use it to test if the application is already active, using the is_active() method. If yes, the application should simply exit. If not, the application should declare its main UI view, using the will_present() method, and present the view. Here is an example:
```
 import app_single_launch

 app = AppSingleLaunch("MyApp")
 if not app.is_active():
     view = MyAppView(app)
     app.will_present(view)
     view.present()
```

An application should make a call to the AppSingleLaunch.will_close() method, from the will_close() method of its main UI view:

 class MyAppView(ui.View):

     def __init__(self, app):
         self.app = app

     def will_close(self):
       self.app.will_close()

Demo

Save the code for app_single_launch.py and the two demo apps in the same directory.

Define home screen shortcuts for the two demo apps.

Launch demo app 1 using its home screen shortcut, type some text in the text field, then relaunch the app using its home screen shortcut : the text typed previously is still showing, meaning we are using the first launched instance, not the second one. Closing the app brings us back to the Pythonista IDE, not to previously piled up instances of the app.

Launch demo app 1 using its home screen shortcut, then Launch demo app 2 using its home screen shortcut, then close it : the Pythonista IDE shows, not a piled up instance of demo app 1.

Et voilà !

app_single_launch.py

""" Ensure a Pythonista script can only be launched once from the iOS home screen.

This module provides a solution to the problem stated by shinyformica, which I
have also encountered (https://forum.omz-software.com/topic/5440/prevent-
duplicate-launch-from-shortcut):
    "Is there a good, canonical way to prevent a script from launching again if
    there is already an instance running? Specifically, I want to prevent the
    scenario where a user launches the script from the home screen via an app
    shortcut, then goes back to the home screen and launches it again.""

The solution is based on a simple protocol, which applications need to adhere
to. When this is the case, applications will not "pile up on top of one another"
when launched from the iOS home screen:
- When an app is already active in Pythonista and it is launched again with its
  home screen shortcut, the new instance of the app detects the situation and
  exits, leaving the already active instance of the app on screen.
- When an app is launched from its home screen shortcut and a previous app is
  already active in Pythonista, the previous app will be notified that it
  should terminate, its main UI view will be closed, and the new app will be
  launched.

Protocol:
1) An application should create an instance of class AppSingleLaunch, and use
   it to test if the application is already active, using the is_active()
   method. If yes, the application should simply exit. If not, the application
   should declare its main UI view, using the will_present() method, and
   present the view. Here is an example:

        import app_single_launch

        app = AppSingleLaunch("MyApp")
        if not app.is_active():
            view = MyAppView(app)
            app.will_present(view)
            view.present()

2) An application should make a call to the AppSingleLaunch.will_close()
   method, from the will_close() method of its main UI view:

        class MyAppView(ui.View):

            def __init__(self, app):
                self.app = app

            def will_close(self):
              self.app.will_close()

Implementation: in order to achieve the desired result, we need to remember the
last application launched according to the protocol, to determine if it is
still active, and, if it is, to close it. This is achieved by storing into a
lock file some information about the last application launched:
- Its name, as passed to single_launch.launching()
- The id of the ui.View instance for its main view, as passed to single_launch.
  launching(). This is later used to determine if the view is still on screen
  (when an object is still associated with the id), and to close the app's view.
  After several tests, it turns out we must use an ui.View object for this
  purpose, as they seem to persist better than other objects after the cleanup
  pykit-preflight.py does when an app is launched from the home screen.
The location of the lock file is defined by global variable LOCK_PATH. The
default location is in the 'site-packages' directory.

Known issue:
- When an app is on screen, then launched again from its home screen shortcut,
  some issues may happen with inline import statements (rare, would need to be
  qualified further).

26-Feb-2019 TPO - Created this module
28-Feb-2019 TPO - Initial release
 3-Mar-2019 TPO - Wrapped the code into the AppSingleLaunch class """


import gc
import json
from pathlib import Path
import time
from typing import Any

import ui


__all__ = [
    'AppSingleLaunch',
]


DEBUG = False
LOCK_PATH = '~/Documents/site-packages/single_launch.lock'


def _object_for_id(id_: int) -> Any:
    """ Return an object, given its id. """

    # Do a complete garbage collect, to avoid false positives in case the
    # object was still in use recently. In the context of AppSingleLaunch,
    # this would happen if an app was closed, then launched again immediately.
    gc.collect()
    for obj in gc.get_objects():
        if id(obj) == id_:
            return obj
    return None


class AppSingleLaunch:
    """ Wrapper class for all module functionnality. """

    def __init__(self, app: str):
        """ Initialize an AppSingleLaunch instance.

        Arguments:
        - app: application name, which should be unique (but this is not
        enforced). """
        self.app = app

    def is_active(self) -> bool:
        """ Test if the application is already active.

        Returns:
        - True if the application is already running, in which case the caller
          should do nothing and exit.
        - False if the application is not already running, in which case the
          caller should launch the application in a normal way, and declare its
          main view by calling the will_present() method."""
        if DEBUG:
            print(f"is_active(), app = {self.app}")
        lock_path = Path(LOCK_PATH).expanduser()
        if lock_path.exists():
            with open(lock_path) as lock_file:
                (lock_app, lock_view_id) = tuple(json.load(lock_file))
            lock_view = _object_for_id(lock_view_id)
            if DEBUG:
                print("- Lock file =", lock_app, lock_view_id,
                      "valid" if lock_view else "invalid")
            if lock_app == self.app and lock_view:
                if DEBUG:
                    print(f"- App {self.app} already active")
                return True
        if DEBUG:
            print(f"- App {self.app} not active")
        return False

    def will_present(self, view: ui.View) -> None:
        """ Declare that the application is about to present its main view.

        Arguments:
        - view: ui.View instance for the app's main view. """
        if DEBUG:
            print(f"will_present({id(view)}), app = {self.app}")
        lock_path = Path(LOCK_PATH).expanduser()
        if lock_path.exists():
            with open(lock_path) as lock_file:
                (lock_app, lock_view_id) = tuple(json.load(lock_file))
            lock_view = _object_for_id(lock_view_id)
            if DEBUG:
                print("- Lock file =", lock_app, lock_view_id,
                      "valid" if lock_view else "invalid")
            if lock_app == self.app and lock_view:
                raise ValueError(f"App {self.app} is already active, cannot "
                                 f"call will_present() against it.")
            else:
                if lock_view and isinstance(lock_view, ui.View):
                    if DEBUG:
                        print(f"- Closing app {lock_app}")
                    lock_view.close()
                    time.sleep(1)  # Required for view to close properly
                # else: lock is a leftover from a previous Pythonista session
                #       and can be safely ignored.
        with open(lock_path, 'w') as lock_file:
            json.dump([self.app, id(view)], lock_file)
        if DEBUG:
            print(f"- Launching app {self.app}\n- Lock file =", self.app, id(view))

    def will_close(self) -> None:
        """ Declare that the application is about to close its main view. """
        lock_path = Path(LOCK_PATH).expanduser()
        if lock_path.exists():
            with open(lock_path) as lock_file:
                (lock_app, lock_view_id) = tuple(json.load(lock_file))
            if lock_app != self.app:
                raise ValueError(f"App {self.app} if not active, "
                                 f"{lock_app} is active")
            lock_path.unlink()

single_launch_demo1.py

""" app_single_launch demo script #1. """
from app_single_launch import AppSingleLaunch
import ui


class MainView(ui.View):
    def __init__(self, app: AppSingleLaunch):
        self.app = app
        self.name = "Demo app 1"
        self.flex = 'WH'
        self.background_color = 'white'
        self.add_subview(ui.TextField(
            width=200,
            height=30,
            placeholder="Type some text"))

    def will_close(self) -> None:
        self.app.will_close()


if __name__ == '__main__':
    app = AppSingleLaunch("Demo app 1")
    if not app.is_active():
        view = MainView(app)
        app.will_present(view)
        view.present()

single_launch_demo2.py

""" app_single_launch demo script #2. """
from app_single_launch import AppSingleLaunch
import ui


class MainView(ui.View):
    def __init__(self, app: AppSingleLaunch):
        self.app = app
        self.name = "Demo app 2"
        self.flex = 'WH'
        self.background_color = 'white'
        self.add_subview(ui.TextField(
            width=200,
            height=30,
            placeholder="Type some text"))

    def will_close(self) -> None:
        self.app.will_close()


if __name__ == '__main__':
    app = AppSingleLaunch("Demo app 2")
    if not app.is_active():
        view = MainView(app)
        app.will_present(view)
        view.present()

TPO

@mikael you are quite right, dir() shows that safari_view_controler has a 'contentScrollView ' attribute.

However, safari_view_controler.contentScrollView() returns None, both in reader_view() and in safariViewControllerDidFinish_() :-(

I have gone through the official Apple doc on SFSafariViewController, 'contentScrollView ' is not mentionned anywhere.

TPO

@mikael : works like a charm, thanks a lot !

TPO

In addition to adopting cvp's SFSafariView solution, I have been experimenting with JonB's initial suggestion of using Safari's JS code for the reader mode.

The reason for this is that SFSafariView is a black box which does not provide a way of getting / setting the position in the page. Being able to do this would allow a newsreader app to remember where the user stopped reading an article, and later re-open the article at this very position. This would be convenient for long articles which cannot be read in one sitting.

If we had a way a generating a Safari-reader-mode-like filtered version of the web page, we could display it in a WebView and then get / set the position (as demonstrated by MarkdownView, https://github.com/mikaelho/pythonista-markdownview) to achieve this result.

I have digged a bit into this, have found a more recent and more complete version of Safari's reader mode source code (both JS and CSS), and have had some success with it:

The web page is cleaned of most useless content
It is displayed in the mode selected (for example : sepia), with the font selected

However:

Not all useless content is removed, and the result is not as good as what Safari produces
Margins and spacing between paragraphs are not handled properly

You will find below my test code and pointers to the Safari sources, in case anyone is interested in investigating this further.

Download the following files :

safari.js : https://github.com/liruqi/Safari/blob/master/safari.js
article-content.css : https://github.com/andjosh/safari-reader-css/blob/master/article-content.css
reader-ui.css : https://github.com/andjosh/safari-reader-css/blob/master/reader-ui.css
theming.css : https://github.com/andjosh/safari-reader-css/blob/master/theming.css

Then run the following in the same directory :

import wkwebview
import ui

with open('safari.js', 'r', encoding='utf-8') as f:
    safari = f.read()

with open('reader-ui.css', 'r', encoding='utf-8') as f:
    reader_ui_css = f.read()

with open('article-content.css', 'r', encoding='utf-8') as f:
    article_content_css = f.read()

with open('theming.css', 'r', encoding='utf-8') as f:
    theming_css = f.read()

js_script = f'''
    r = new ReaderArticleFinder(document);
    document.body.innerHTML = r.articleNode().innerHTML;
    document.body.classList="system sepia";
    var style = document.createElement('style');
    style.innerHTML = `{reader_ui_css}\n{article_content_css}\n{theming_css}`;
    var ref = document.querySelector('script');
    ref.parentNode.insertBefore(style, ref);
    document.getElementById("dynamic-article-content").sheet.insertRule("#article {{ font-size:15 px; line-height:25px; }}"); '''


class Delegate:

    @ui.in_background
    def webview_did_finish_load(self, webview):
        w.eval_js(js_script)


w = wkwebview.WKWebView(delegate=Delegate())
w.present()
w.add_script(safari)
w.load_url('https://www.technologyreview.com/s/612929/wristwatch-heart-monitors-might-save-your-lifeand-change-medicine-too/')

TPO

I have packaged cvp's solution into a module, which works like a charm, thanks a lot cvp ! (I use it for a newsreader).

I have come across two limitations, though:

reader_view() cannot be used if 'uiview' has a NavigationView, or if any view presented below it has a NavigationView (even if the view has no relationship with 'uiview' - very strange)
No resizing is performed when the reader view changes orientation

I am not very proficient with objc, would anyone know how to improve this ?

""" Modal view which displays a web page in reader mode.

Based on cvp's code:
https://forum.omz-software.com/topic/5392/webview-and-reader-mode/18

When run as a script, the module shows a small demo application.

Implementation note:

    Transmitting the callback function from reader_view() to safariView-
    ControllerDidFinish_() turns out to be trickier than expected, especially
    when combining reader_view.py with app_single_launch.py.

    In this case, when the user launches the same app a second time, a new
    'safari_view_controler' instance seems to be created automagically. We
    therefore cannot store the callback function as one of the 'safari_view_
    controler's properties, since the instance created by reader_view() is
    silently replaced by a new instance when the app is relaunched, and
    ControllerDidFinish_() will receive the new instance, not the old one.

    In the end, the simplest solution works, i.e. storing the callback in a
    global. This does of course come with theoretical limitations: an applica-
    tion should not make a second call to reader_view() until the reader view
    displayed by the first call has been closed. This should not be too much of
    an issue, as I really cannot imagine a practical use case for doing this. I
    have included a simple protection against this edge case anyway.

Revision history:
 6-Fev-2019 TPO - Initial release
28-Fev-2019 TPO - Added the 'enter_reader_mode' argument to reader_view()
 7-Mar-2019 TPO - reader_view() now works when used with app_single_launch.py """


from typing import Callable, Optional

from objc_util import create_objc_class, nsurl, ObjCClass, ObjCInstance
import ui


__all__ = [
    'reader_view',
]


Callback = Callable[[], None]
__CALLBACK: Optional[Callback]
__READER_VIEW_DISPLAYED = False


def safariViewControllerDidFinish_(_self, _cmd, _controller):
    global __CALLBACK, __READER_VIEW_DISPLAYED
    if __CALLBACK:
        __CALLBACK()
    __READER_VIEW_DISPLAYED = False


def reader_view(url: str,
                uiview: ui.View,
                callback: Optional[Callback] = None,
                enter_reader_mode: bool = True) -> None:
    """ Modal view which displays a web page in reader mode.

    Arguments:
    - url: of the web page to be displayed. The only URL schemes allowed are
      http and https.  Any other URL scheme will raise an Objective-C exception
      and cause Pythonista to be terminated.
    - uiview: ui.View instance on which the web view is to be displayed. Note
      that reader_view() does not work if this is an instance of ui.Navigation-
      View.
    - callback: function of no argument, which is called when the user closes
      the view.
    - enter_reader_mode: if true and if reader mode is available, it will be
      entered automatically; if false, the user will have to tap the reader
      mode icon to enter reader mode (when available). """
    global __CALLBACK, __READER_VIEW_DISPLAYED
    if __READER_VIEW_DISPLAYED:
        raise ValueError("reader_view() already in use")
    __READER_VIEW_DISPLAYED = True
    __CALLBACK = callback

    MySFSafariViewControllerDelegate = create_objc_class(
        'MySFSafariViewControllerDelegate',
        methods=[safariViewControllerDidFinish_],
        protocols=['SFSafariViewControllerDelegate'])
    delegate = MySFSafariViewControllerDelegate.alloc().init()
    safari_view_controler_conf = (
        ObjCClass('SFSafariViewControllerConfiguration').alloc().init())
    safari_view_controler_conf.setEntersReaderIfAvailable_(enter_reader_mode)
    safari_view_controler = ObjCClass('SFSafariViewController').alloc() \
        .initWithURL_configuration_(nsurl(url), safari_view_controler_conf)
    safari_view_controler.delegate = delegate
    safari_view_controler.setModalPresentationStyle_(3)  # 3 = currentContext
    vc = ObjCClass('SUIViewController').viewControllerForView_(ObjCInstance(uiview))
    vc.presentViewController_animated_completion_(safari_view_controler, True, None)


if __name__ == '__main__':
    from datetime import datetime

    def done():
        print("After user has closed reader view", datetime.now())

    def test(sender):
        print("Before call to reader_view()", datetime.now())
        reader_view(url=url, uiview=view, callback=done)

    url = 'http://www.nytimes.com/2019/01/29/climate/global-warming-extreme-weather.html'
    view = ui.View(
        flex='WH',
        background_color='white',
        name='reader_view demo',
        right_button_items=[ui.ButtonItem(title='test', action=test)])
    view.present()

TPO

@cvp, it works, you're the greatest !!!

TPO

@TPO

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