New Demo - Design pattern for main func, window create, and saving theme from one run to the next

DemoPrograms/Demo_Design_Pattern_Save_Theme.py

@@ -0,0 +1,46 @@
+import PySimpleGUI as sg
+
+"""
+    Demo - Basic window design pattern
+    * Creates window in a separate function for easy "restart"
+    * Saves theme as a user variable
+    * Puts main code into a main function so that multiprocessing works if you later convert to use
+    
+    Copyright 2020 PySimpleGUI.org
+"""
+
+
+# ------------------- Create the window -------------------
+def make_window():
+    # Set theme based on previously saved
+    sg.theme(sg.user_settings_get_entry('theme', None))
+
+    # -----  Layout & Window Create  -----
+    layout = [[sg.T('This is your layout')],
+               [sg.OK(), sg.Button('Theme', key='-THEME-'), sg.Button('Exit')]]
+
+    return sg.Window('Pattern for theme saving', layout)
+
+
+# ------------------- Main Program and Event Loop -------------------
+
+def main():
+    window = make_window()
+
+    while True:
+        event, values = window.read()
+        if event == sg.WINDOW_CLOSED or event == 'Exit':
+            break
+        if event == '-THEME-':      # Theme button clicked, so get new theme and restart window
+            ev, vals = sg.Window('Choose Theme', [[sg.Combo(sg.theme_list(), k='-THEME LIST-'), sg.OK(), sg.Cancel()]]).read(close=True)
+            if ev == 'OK':
+                window.close()
+                sg.user_settings_set_entry('theme', vals['-THEME LIST-'])
+                window = make_window()
+
+    window.close()
+
+
+if __name__ == '__main__':
+    main()
+