Demo program for read all windows that was evidently not checked in....

DemoPrograms/Demo_Multi_Window_read_all_windows.py

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+import PySimpleGUI as sg
+
+"""
+    Read all windows example
+    The input elements are shown as output on the other window when "Go" is pressed
+    The checkboxes on window 1 are mirrored on window 2 if "mirror" checkbox is set
+    
+    Copyright 2022 PySimpleGUI
+"""
+layout1 = [  [sg.Text('My Window')],
+            [sg.Input(k='-IN-'), sg.Text(k='-OUT-')],
+             [sg.CB('Check 1', k='-CB1-', enable_events=True), sg.CB('Check 2', k='-CB2-', enable_events=True), sg.CB('Mirror on Window 2', enable_events=True, k='-CB3-')],
+            [sg.Button('Go'), sg.Button('Exit')]  ]
+
+window1 = sg.Window('Window 1 Title', layout1, finalize=True, grab_anywhere=True, relative_location=(-600, 0))
+
+layout2 = [  [sg.Text('My Window')],
+            [sg.Input(k='-IN-'), sg.Text(k='-OUT-')],
+             [sg.CB('Check 1', k='-CB1-'), sg.CB('Check 2', k='-CB2-')],
+             [sg.Button('Go'),  sg.Button('Exit')]  ]
+
+window2 = sg.Window('Window 2 Title', layout2, finalize=True,  grab_anywhere=True)
+
+while True:             # Event Loop
+    window, event, values = sg.read_all_windows()
+    if window is None:
+        print('exiting because no windows are left')
+        break
+    print(window.Title, event, values) if window is not None else None
+    if event == sg.WIN_CLOSED or event == 'Exit':
+        window.close()
+    if event == 'Go':
+        # Output the input element to the other windwow
+        try:        # try to update the other window
+            if window == window1:
+                window2['-OUT-'].update(values['-IN-'])
+            else:
+                window1['-OUT-'].update(values['-IN-'])
+        except:
+            pass
+    try:
+        if window == window1 and values['-CB3-']:
+            window2['-CB1-'].update(values['-CB1-'])
+            window2['-CB2-'].update(values['-CB2-'])
+    except:
+        pass