Deprecate 'x' argument for widgets.TextBox.begin_typing

This argument is a holdover from seemingly a debugging print statement
that has long since been removed.

It is not used internally, and was passed entirely different things in
the two places it was called (once in tests, once in library code).

Author: ksunden

lib/matplotlib/tests/test_widgets.py

@@ -982,7 +982,7 @@ def test_TextBox(ax, toolbar):
     assert tool.text == 'x**2'
     assert text_change_event.call_count == 1
 
-    tool.begin_typing(tool.text)
+    tool.begin_typing()
     tool.stop_typing()
 
     assert submit_event.call_count == 2

lib/matplotlib/widgets.py

@@ -1279,7 +1279,8 @@ def set_val(self, val):
             self._observers.process('change', self.text)
             self._observers.process('submit', self.text)
 
-    def begin_typing(self, x):
+    @_api.delete_parameter("3.7", "x")
+    def begin_typing(self, x=None):
         self.capturekeystrokes = True
         # Disable keypress shortcuts, which may otherwise cause the figure to
         # be saved, closed, etc., until the user stops typing.  The way to
@@ -1326,7 +1327,7 @@ def _click(self, event):
         if event.canvas.mouse_grabber != self.ax:
             event.canvas.grab_mouse(self.ax)
         if not self.capturekeystrokes:
-            self.begin_typing(event.x)
+            self.begin_typing()
         self.cursor_index = self.text_disp._char_index_at(event.x)
         self._rendercursor()