Fix tk tooltips for dark themes.

anntzer · anntzer · commit 0c8afdde2c34 · 2020-06-25T16:13:12.000+02:00
Not setting the background explicitly to a light color is sufficient to avoid having white text on a light color when using a dark desktop theme. (The forced background color goes back to when ToolTip was introduced, in c887139, with no comment as to why.)
diff --git a/lib/matplotlib/backends/_backend_tk.py b/lib/matplotlib/backends/_backend_tk.py
@@ -684,7 +684,7 @@ def showtip(self, text):
         except tk.TclError:
             pass
         label = tk.Label(tw, text=self.text, justify=tk.LEFT,
-                         background="#ffffe0", relief=tk.SOLID, borderwidth=1)
+                         relief=tk.SOLID, borderwidth=1)
         label.pack(ipadx=1)
 
     def hidetip(self):
