Implement set_history_buttons for Tk toolbar.

QuLogic · QuLogic · commit edbca79a281a · 2020-04-20T18:12:55.000-04:00
This makes the backward/forward buttons change enabled state based on
whether there are actually old/new views available.
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -643,6 +643,16 @@ def save_figure(self, *args):
         except Exception as e:
             tkinter.messagebox.showerror("Error saving file", str(e))
 
+    def set_history_buttons(self):
+        if self._nav_stack._pos > 0:
+            self._buttons['Back']['state'] = 'normal'
+        else:
+            self._buttons['Back']['state'] = 'disabled'
+        if self._nav_stack._pos < len(self._nav_stack._elements) - 1:
+            self._buttons['Forward']['state'] = 'normal'
+        else:
+            self._buttons['Forward']['state'] = 'disabled'
+
 
 class ToolTip:
     """
