Update morphic.txt

morphic.txt

@@ -7,9 +7,9 @@
     written by Jens Mönig
     [email protected]
 
-    Copyright (C) 2010-2022 by Jens Mönig
+    Copyright (C) 2010-2024 by Jens Mönig
 
-    This documentation last changed: November 22
+    This documentation last changed: June 04, 2024
 
     This file is part of Snap!.
 
@@ -50,6 +50,7 @@
             (f) resize event
             (g) combined mouse-keyboard events
             (h) text editing events
+            (i) indicating unsaved changes
         (4) stepping
         (5) creating new kinds of morphs
             (a) drawing the shape
@@ -857,6 +858,19 @@
     single-line text elements can hold them apart.
 
 
+    (i) indicating unsaved changes
+    ------------------------------
+    Before closing a browser tab with a Morphic world any top level morph
+    can signal unsaved changes by implementing a
+
+        hasUnsavedChanges()
+
+    method, which returns a Boolean value indicating whether it is safe to
+    destroy. If any top level morph indicates unsaved changes the browser
+    pops up a dialog box warning about unsaved changes and prompting for user
+    confirmation to close it.
+
+
     (4) stepping
     ------------
     Stepping is what makes Morphic "magical". Two properties control