From c82516bee6a2c433542e6f7e6551820581b8379d Mon Sep 17 00:00:00 2001
From: PySimpleGUI <PySimpleGUI@PySimpleGUI.com>
Date: Thu, 22 Jul 2021 15:27:06 -0400
Subject: [PATCH] A "lengthy function call" demo - another approach to using
 threads

---
 .../Demo_Multithreaded_Wrapper_Func.py        | 109 ++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 DemoPrograms/Demo_Multithreaded_Wrapper_Func.py

diff --git a/DemoPrograms/Demo_Multithreaded_Wrapper_Func.py b/DemoPrograms/Demo_Multithreaded_Wrapper_Func.py
new file mode 100644
index 00000000..4ea9513a
--- /dev/null
+++ b/DemoPrograms/Demo_Multithreaded_Wrapper_Func.py
@@ -0,0 +1,109 @@
+import threading
+import time
+import PySimpleGUI as sg
+
+"""
+    Performing function calls that are lengthy using a "wrapper function)
+
+    This is one way to use threads and PySimpleGUI's write_event_value to enable users
+        to call functions that would normally cause a GUI to appear hung.
+
+    A helper function, perform_long_operation is used where a function call is normally done in your code.
+
+    Instead of directly calling the function, a lambda is used and passed to the helper function along with
+        the window that will receive the results and a key that is used to signal that the function
+        has completed running.
+
+    Copyright 2021 PySimpleGUI
+"""
+
+'''
+M""""""""M dP                                        dP
+Mmmm  mmmM 88                                        88
+MMMM  MMMM 88d888b. 88d888b. .d8888b. .d8888b. .d888b88
+MMMM  MMMM 88'  `88 88'  `88 88ooood8 88'  `88 88'  `88
+MMMM  MMMM 88    88 88       88.  ... 88.  .88 88.  .88
+MMMM  MMMM dP    dP dP       `88888P' `88888P8 `88888P8
+MMMMMMMMMM
+'''
+
+def perform_long_operation(func, window, end_key):
+    thread = threading.Thread(target=long_func_thread, args=(window, end_key, func))
+    thread.start()
+
+
+def long_func_thread(window: sg.Window, end_key, original_func):
+    return_value = original_func()
+    window.write_event_value(end_key,  return_value)
+
+
+'''
+M""MMMMM""M                            
+M  MMMMM  M                            
+M  MMMMM  M .d8888b. .d8888b. 88d888b. 
+M  MMMMM  M Y8ooooo. 88ooood8 88'  `88 
+M  `MMM'  M       88 88.  ... 88       
+Mb       dM `88888P' `88888P' dP       
+MMMMMMMMMMM                            
+                                       
+MM""""""""`M                            
+MM  mmmmmmmM                            
+M'      MMMM dP    dP 88d888b. .d8888b. 
+MM  MMMMMMMM 88    88 88'  `88 88'  `"" 
+MM  MMMMMMMM 88.  .88 88    88 88.  ... 
+MM  MMMMMMMM `88888P' dP    dP `88888P' 
+MMMMMMMMMMMM
+'''
+
+
+def my_long_func(count, a=1, b=2):
+    """
+    This is your function that takes a long time
+    :param count:
+    :param a:
+    :param b:
+    :return:
+    """
+    for i in range(count):
+        print(i, a, b)
+        time.sleep(.5)
+    return 'DONE!'
+
+
+'''
+                    oo
+
+88d8b.d8b. .d8888b. dP 88d888b.
+88'`88'`88 88'  `88 88 88'  `88
+88  88  88 88.  .88 88 88    88
+dP  dP  dP `88888P8 dP dP    dP
+'''
+
+
+def main():
+    layout = [  [sg.Text('Long running function call design pattern')],
+                [sg.Text('How many times to run the loop?'), sg.Input(s=(4,1), key='-IN-')],
+                [sg.Text(s=(30,1), k='-STATUS-')],
+                [sg.Button('Go', bind_return_key=True), sg.Button('Exit')]  ]
+
+    window = sg.Window('Window Title', layout)
+
+    while True:             # Event Loop
+        event, values = window.read()
+        print(event, values)
+        if event == sg.WIN_CLOSED or event == 'Exit':
+            break
+        elif event == 'Go':
+            window['-STATUS-'].update('Calling your function...')
+            if values['-IN-'].isnumeric():
+                # This is where the magic happens.  Add your function call as a lambda
+                perform_long_operation(lambda : my_long_func(int(values['-IN-']), a=10),
+                                       window, '-END KEY-')
+            else:
+                window['-STATUS-'].update('Try again... how about an int?')
+        elif event == '-END KEY-':
+            window['-STATUS-'].update(f'Completed. Returned: {values[event]}')
+    window.close()
+
+if __name__ == '__main__':
+    main()