New Demo that shows how to "pin" a location of an element in a layout so that it can be returned to the correct location when changing from invisible to visible

DemoPrograms/Demo_Invisible_Elements_Pinning.py

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+import PySimpleGUI as sg
+
+"""
+    Demo - "Pinning" an element into a location in a layout
+
+    When using the tkinter port of PySimpleGUI, if you make an element invisible and then visible again,
+    rather than the element appearing where it was originally located, it will be moved to the bottom
+    of whatever it was contained within (a window or a container element (column, frame, tab))
+
+    This demo adds a function "pin" which will place the element inside of a Column element.  This will
+    reserve a location for the element to be returned.
+    
+    For other ports of PySimpleGUI such as the Qt port, the position is remembered by Qt and as a
+    result this technique using Columns is not needed.
+    
+    Copyright 2020 PySimpleGUI.org
+"""
+
+def pin(elem):
+    '''
+    Pin's an element provided into a layout so that when it's made invisible and visible again, it will
+     be in the correct place.  Otherwise it will be placed at the end of its containing window/column.
+
+    :param elem: the element to put into the layout
+    :return: A column element containing the provided element
+    '''
+    return sg.Column([[elem]], pad=(0,0))
+
+
+layout = [  [sg.Text('Window with Hidden Button')],
+            [sg.Input(key='-IN-')],
+            [pin(sg.Button('Button1')), pin(sg.Button('Button2')), sg.B('Button3')],
+        ]
+
+window = sg.Window('Window Title', layout)
+
+toggle = False
+while True:             # Event Loop
+    event, values = window.read()
+    print(event, values)
+    if event == sg.WIN_CLOSED or event == 'Exit':
+        break
+
+    window['Button2'].update(visible=toggle)
+    toggle = not toggle
+
+window.close()