Remove Fonts.{set_canvas_size,width,height,descent,get_results}.

We can just inline the calls directly to the backend itself at the sole
use site (in _parse_cached).  The width, height, and depth attributes on
Fonts are never used either.

Author: anntzer

lib/matplotlib/_mathtext.py

@@ -140,15 +140,6 @@ def get_metrics(self, font, font_class, sym, fontsize, dpi, math=True):
         info = self._get_info(font, font_class, sym, fontsize, dpi, math)
         return info.metrics
 
-    def set_canvas_size(self, w, h, d):
-        """
-        Set the size of the buffer used to render the math expression.
-        Only really necessary for the bitmap backends.
-        """
-        self.width, self.height, self.depth = np.ceil([w, h, d])
-        self.mathtext_backend.set_canvas_size(
-            self.width, self.height, self.depth)
-
     @_api.rename_parameter("3.4", "facename", "font")
     def render_glyph(self, ox, oy, font, font_class, sym, fontsize, dpi):
         """
@@ -185,15 +176,6 @@ def get_used_characters(self):
         """
         return self.used_characters
 
-    def get_results(self, box):
-        """
-        Get the data needed by the backend to render the math
-        expression.  The return value is backend-specific.
-        """
-        result = self.mathtext_backend.get_results(
-            box, self.get_used_characters())
-        return result
-
     def get_sized_alternatives_for_symbol(self, fontname, sym):
         """
         Override if your font provides multiple sizes of the same

lib/matplotlib/mathtext.py

@@ -256,8 +256,8 @@ def _parse_cached(self, s, dpi, prop):
             self.__class__._parser = _mathtext.Parser()
 
         box = self._parser.parse(s, font_output, fontsize, dpi)
-        font_output.set_canvas_size(box.width, box.height, box.depth)
-        return font_output.get_results(box)
+        backend.set_canvas_size(*np.ceil([box.width, box.height, box.depth]))
+        return backend.get_results(box)
 
 
 def math_to_image(s, filename_or_obj, prop=None, dpi=None, format=None,