Merge pull request #3151 from PySimpleGUI/Dev-latest

New Multi-threaded demo - requires GitHub version of PySimpleGUI.py

DemoPrograms/Demo_Multithreaded_Write_Event_Value.py

@@ -0,0 +1,61 @@
+import PySimpleGUI as sg
+import threading
+import time
+
+"""
+    Threaded Demo - Uses Window.write_event_value communications
+    
+    Requires PySimpleGUI.py version 4.24.0.17
+
+    Demo of threads using a new way of communicating with threads that is done in a non-polled way.
+    No longer do you need to run your event loop with a timeout value in order to multi-thread.
+    Now you can pend on your read forever and use a special call that threads can call that will add a new item to the queue
+    of items
+
+"""
+
+THREAD_EVENT = '-THEAD-'
+
+def the_thread(window):
+    """
+    The thread that communicates with the application through the window's events.
+
+    Once a second wakes and sends a new event and associated value to the window
+    """
+    i = 0
+    while True:
+        time.sleep(1)
+        window.write_event_value(THREAD_EVENT, i)
+        i += 1
+
+
+def main():
+    """
+    The demo will display in the multiline info about the event and values dictionary as it is being
+    returned from window.read()
+    Every time "Start" is clicked a new thread is started
+    Try clicking "go" to see that the window is active while the thread stuff is happening in the background
+    """
+
+    layout = [  [sg.Text('My Window')],
+                [sg.Multiline(size=(40,20), key='-ML-', autoscroll=True, reroute_stdout=True, write_only=True, reroute_cprint=True)],
+                [sg.Input(key='-IN-')],
+                [sg.Button('Go'), sg.B('Start'), sg.Button('Exit')]  ]
+
+    window = sg.Window('Window Title', layout)
+
+    while True:             # Event Loop
+        event, values = window.read()
+        sg.cprint(event, values)
+        if event == sg.WIN_CLOSED or event == 'Exit':
+            break
+        if event == 'Start':
+            thread = threading.Thread(target=the_thread, args=(window,), daemon=True)
+            thread.start()
+        if event == THREAD_EVENT:
+            sg.cprint(f'Data from the thread = {values[THREAD_EVENT]}', colors='white on red')
+    window.close()
+
+
+if __name__ == '__main__':
+    main()