matplotlib · timhoffm · Oct 10, 2020 · Sep 10, 2020
diff --git a/doc/api/next_api_changes/behavior/17791-AL.rst b/doc/api/next_api_changes/behavior/17791-AL.rst
@@ -1,9 +1,9 @@
-GTK key name changes
-~~~~~~~~~~~~~~~~~~~~
+GTK/Tk key name changes
+~~~~~~~~~~~~~~~~~~~~~~~
 
 The handling of non-ASCII keypresses (as reported in the KeyEvent passed to
-``key_press_event``-handlers) in the GTK backends now correctly reports Unicode
-characters (e.g., €), and respects NumLock on the numpad.
+``key_press_event``-handlers) in the GTK and Tk backends now correctly reports
+Unicode characters (e.g., €), and better respects NumLock on the numpad.
 
 The following key names have changed; the new names are consistent with those
 reported by the Qt backends:

diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -113,70 +113,6 @@ def _on_timer(self):
 class FigureCanvasTk(FigureCanvasBase):
     required_interactive_framework = "tk"
 
-    keyvald = {65507: 'control',
-               65505: 'shift',
-               65513: 'alt',
-               65515: 'super',
-               65508: 'control',
-               65506: 'shift',
-               65514: 'alt',
-               65361: 'left',
-               65362: 'up',
-               65363: 'right',
-               65364: 'down',
-               65307: 'escape',
-               65470: 'f1',
-               65471: 'f2',
-               65472: 'f3',
-               65473: 'f4',
-               65474: 'f5',
-               65475: 'f6',
-               65476: 'f7',
-               65477: 'f8',
-               65478: 'f9',
-               65479: 'f10',
-               65480: 'f11',
-               65481: 'f12',
-               65300: 'scroll_lock',
-               65299: 'break',
-               65288: 'backspace',
-               65293: 'enter',
-               65379: 'insert',
-               65535: 'delete',
-               65360: 'home',
-               65367: 'end',
-               65365: 'pageup',
-               65366: 'pagedown',
-               65438: '0',
-               65436: '1',
-               65433: '2',
-               65435: '3',
-               65430: '4',
-               65437: '5',
-               65432: '6',
-               65429: '7',
-               65431: '8',
-               65434: '9',
-               65451: '+',
-               65453: '-',
-               65450: '*',
-               65455: '/',
-               65439: 'dec',
-               65421: 'enter',
-               }
-
-    _keycode_lookup = {
-                       262145: 'control',
-                       524320: 'alt',
-                       524352: 'alt',
-                       1048584: 'super',
-                       1048592: 'super',
-                       131074: 'shift',
-                       131076: 'shift',
-                       }
-    """_keycode_lookup is used for badly mapped (i.e. no event.key_sym set)
-       keys on apple keyboards."""
-
     def __init__(self, figure, master=None, resize_callback=None):
         super().__init__(figure)
         self._idle = True
@@ -332,16 +268,7 @@ def scroll_event_windows(self, event):
             FigureCanvasBase.scroll_event(self, x, y, step, guiEvent=event)
 
     def _get_key(self, event):
-        val = event.keysym_num
-        if val in self.keyvald:
-            key = self.keyvald[val]
-        elif (val == 0 and sys.platform == 'darwin'
-              and event.keycode in self._keycode_lookup):
-            key = self._keycode_lookup[event.keycode]
-        elif val < 256:
-            key = chr(val)
-        else:
-            key = None
+        key = cbook._unikey_or_keysym_to_mplkey(event.char, event.keysym)
 
         # add modifier keys to the key string. Bit details originate from
         # http://effbot.org/tkinterbook/tkinter-events-and-bindings.htm

diff --git a/lib/matplotlib/backends/backend_gtk3.py b/lib/matplotlib/backends/backend_gtk3.py
@@ -207,17 +207,9 @@ def size_allocate(self, widget, allocation):
         self.draw_idle()
 
     def _get_key(self, event):
-        key = chr(Gdk.keyval_to_unicode(event.keyval))
-        if not key.isprintable():
-            key = Gdk.keyval_name(event.keyval).lower()
-            if key.startswith("kp_"):  # keypad_x (including kp_enter).
-                key = key[3:]
-            if key.startswith("page_"):  # page_{up,down}
-                key = key.replace("page_", "page")
-            if key.endswith(("_l", "_r")):  # alt_l, ctrl_l, shift_l.
-                key = key[:-2]
-            if key == "enter":
-                key = "return"
+        key = cbook._unikey_or_keysym_to_mplkey(
+            chr(Gdk.keyval_to_unicode(event.keyval)),
+            Gdk.keyval_name(event.keyval))
         modifiers = [
                      (Gdk.ModifierType.MOD4_MASK, 'super'),
                      (Gdk.ModifierType.MOD1_MASK, 'alt'),

diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -2334,3 +2334,28 @@ def _format_approx(number, precision):
     Remove trailing zeros and possibly the decimal point.
     """
     return f'{number:.{precision}f}'.rstrip('0').rstrip('.') or '0'
+
+
+def _unikey_or_keysym_to_mplkey(unikey, keysym):
+    """
+    Convert a Unicode key or X keysym to a Matplotlib key name.
+
+    The Unicode key is checked first; this avoids having to list most printable
+    keysyms such as ``EuroSign``.
+    """
+    # For non-printable characters, gtk3 passes "\0" whereas tk passes an "".
+    if unikey and unikey.isprintable():
+        return unikey
+    key = keysym.lower()
+    if key.startswith("kp_"):  # keypad_x (including kp_enter).
+        key = key[3:]
+    if key.startswith("page_"):  # page_{up,down}
+        key = key.replace("page_", "page")
+    if key.endswith(("_l", "_r")):  # alt_l, ctrl_l, shift_l.
+        key = key[:-2]
+    key = {
+        "enter": "return",
+        "prior": "pageup",  # Used by tk.
+        "next": "pagedown",  # Used by tk.
+    }.get(key, key)
+    return key