From 35f5958c4cd4f78f6d9eb42fbfebf5b341bfdd8d Mon Sep 17 00:00:00 2001
From: MikeTheWatchGuy <mike_barnett@hotmail.com>
Date: Sat, 2 Mar 2019 13:31:34 -0500
Subject: [PATCH] New design pattern

---
 DemoPrograms/Demo_Multithreaded_Queued.py | 71 +++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 DemoPrograms/Demo_Multithreaded_Queued.py

diff --git a/DemoPrograms/Demo_Multithreaded_Queued.py b/DemoPrograms/Demo_Multithreaded_Queued.py
new file mode 100644
index 00000000..09ebf8ac
--- /dev/null
+++ b/DemoPrograms/Demo_Multithreaded_Queued.py
@@ -0,0 +1,71 @@
+from queue import Queue
+from threading import Thread
+from time import sleep
+
+import PySimpleGUI as sg
+
+"""
+    DESIGN PATTERN - Multithreaded GUI
+    One method for running multiple threads in a PySimpleGUI environment.
+    This design pattern works for all of the flavors of PySimpleGUI including the Web and also repl.it
+    
+"""
+
+
+def worker_thread(thread_name, run_freq,  gui_queue):
+    """
+    A worker thrread that communicates with the GUI
+    These threads can call functions that block withouth affecting the GUI (a good thing)
+    :param thread_name: Text name used  for displaying info
+    :param run_freq: How often the thread should run in milliseconds
+    :param gui_queue: Queue used to communicate with the GUI
+    :return:
+    """
+    print('Strarting thread - ', thread_name)
+    i = 0
+    while True:
+        sleep(run_freq/1000)
+        gui_queue.put('{} - {}'.format(thread_name, i))
+        i += 1
+
+
+def the_gui(gui_queue):
+    """
+    starts and executes the GUI.  Returns when the user exits / closes the window
+    reads data from a Queue and displays the data
+    :param gui_queue: Queue the GUI should read from
+    :return:
+    """
+    layout = [ [sg.Text('Your GUI Window')],
+               [sg.Text('', size=(15,1), key='_OUTPUT_')],
+               [sg.Button('Exit')],]
+
+    window = sg.Window('Window Title').Layout(layout)
+
+    while True:             # Event Loop
+        event, values = window.Read(timeout=200)        # wait for up to 200 ms for a GUI event
+        if event is None or event == 'Exit':
+            break
+        #--------------- Handle stuff coming in from threads ---------------
+        try:                    # see if something has been posted to Queue
+            message = gui_queue.get_nowait()
+        except:
+            message = None      # indicate nothing posted
+        # if message received from queue, display the message in the Window
+        if message:
+            window.Element('_OUTPUT_').Update(message)
+
+    # if user exits the window, then close the window and exit
+    window.Close()
+
+
+if __name__ == '__main__':
+    #-- Create a Queue to communicate with GUI --
+    gui_queue = Queue()             # queue used to communicate between the gui and the worker
+    #-- Start worker threads, one runs twice as often as the other
+    thread = Thread(target=worker_thread, args=('Thread 1', 1000, gui_queue,),  daemon=True)
+    thread.start()
+    thread = Thread(target=worker_thread, args=('Thread 2', 500, gui_queue,),  daemon=True)
+    thread.start()
+    #-- Start the GUI passing in the Queue --
+    the_gui(gui_queue)