Patch #707701: Expect '??' in event fields. Fixes #698517.

Will backport to 2.2.

Lib/lib-tk/Tkinter.py

@@ -1035,38 +1035,54 @@ def _substitute(self, *args):
         """Internal function."""
         if len(args) != len(self._subst_format): return args
         getboolean = self.tk.getboolean
+
         getint = int
+        def getint_event(s):
+            """Tk changed behavior in 8.4.2, returning "??" rather more often."""
+            try:
+                return int(s)
+            except ValueError:
+                return s
+
         nsign, b, f, h, k, s, t, w, x, y, A, E, K, N, W, T, X, Y, D = args
         # Missing: (a, c, d, m, o, v, B, R)
         e = Event()
+        # serial field: valid vor all events
+        # number of button: ButtonPress and ButtonRelease events only
+        # height field: Configure, ConfigureRequest, Create,
+        # ResizeRequest, and Expose events only
+        # keycode field: KeyPress and KeyRelease events only
+        # time field: "valid for events that contain a time field"
+        # width field: Configure, ConfigureRequest, Create, ResizeRequest,
+        # and Expose events only
+        # x field: "valid for events that contain a x field"
+        # y field: "valid for events that contain a y field"
+        # keysym as decimal: KeyPress and KeyRelease events only
+        # x_root, y_root fields: ButtonPress, ButtonRelease, KeyPress,
+        # KeyRelease,and Motion events
         e.serial = getint(nsign)
-        e.num = getint(b)
+        e.num = getint_event(b)
         try: e.focus = getboolean(f)
         except TclError: pass
-        e.height = getint(h)
+        e.height = getint_event(h)
-        e.keycode = getint(k)
+        e.keycode = getint_event(k)
-        # For Visibility events, event state is a string and
+        e.state = getint_event(s)
-        # not an integer:
+        e.time = getint_event(t)
-        try:
+        e.width = getint_event(w)
-            e.state = getint(s)
+        e.x = getint_event(x)
-        except ValueError:
+        e.y = getint_event(y)
-            e.state = s
-        e.time = getint(t)
-        e.width = getint(w)
-        e.x = getint(x)
-        e.y = getint(y)
         e.char = A
         try: e.send_event = getboolean(E)
         except TclError: pass
         e.keysym = K
-        e.keysym_num = getint(N)
+        e.keysym_num = getint_event(N)
         e.type = T
         try:
             e.widget = self._nametowidget(W)
         except KeyError:
             e.widget = W
-        e.x_root = getint(X)
+        e.x_root = getint_event(X)
-        e.y_root = getint(Y)
+        e.y_root = getint_event(Y)
         try:
             e.delta = getint(D)
         except ValueError: