Merge pull request matplotlib#12933 from anntzer/latexmanagerfactory

Deprecate backend_pgf.LatexManagerFactory.

Author: jklymak

doc/api/next_api_changes/2018-12-05-AL.rst

@@ -0,0 +1,4 @@
+Deprecations
+````````````
+
+The ``backend_pgf.LatexManagerFactory`` class is deprecated.

lib/matplotlib/backends/backend_pgf.py

@@ -1,5 +1,6 @@
 import atexit
 import codecs
+import functools
 import logging
 import math
 import os
@@ -187,6 +188,7 @@ def __init__(self, message, latex_output=""):
         self.latex_output = latex_output
 
 
+@cbook.deprecated("3.1")
 class LatexManagerFactory:
     previous_instance = None
 
@@ -223,14 +225,31 @@ def _build_latex_header():
         # Create LaTeX header with some content, else LaTeX will load some math
         # fonts later when we don't expect the additional output on stdout.
         # TODO: is this sufficient?
-        latex_header = [r"\documentclass{minimal}",
-                        latex_preamble,
-                        latex_fontspec,
-                        r"\begin{document}",
-                        r"text $math \mu$",  # force latex to load fonts now
-                        r"\typeout{pgf_backend_query_start}"]
+        latex_header = [
+            # Include TeX program name as a comment for cache invalidation.
+            r"% !TeX program = {}".format(rcParams["pgf.texsystem"]),
+            r"\documentclass{minimal}",
+            latex_preamble,
+            latex_fontspec,
+            r"\begin{document}",
+            r"text $math \mu$",  # force latex to load fonts now
+            r"\typeout{pgf_backend_query_start}",
+        ]
         return "\n".join(latex_header)
 
+    @classmethod
+    def _get_cached_or_new(cls):
+        """
+        Return the previous LatexManager if the header and tex system did not
+        change, or a new instance otherwise.
+        """
+        return cls._get_cached_or_new_impl(cls._build_latex_header())
+
+    @classmethod
+    @functools.lru_cache(1)
+    def _get_cached_or_new_impl(cls, header):  # Helper for _get_cached_or_new.
+        return cls()
+
     @staticmethod
     def _cleanup_remaining_instances():
         unclean_instances = list(LatexManager._unclean_instances)
@@ -388,7 +407,7 @@ def __init__(self, figure, fh, dummy=False):
         self.image_counter = 0
 
         # get LatexManager instance
-        self.latexManager = LatexManagerFactory.get_latex_manager()
+        self.latexManager = LatexManager._get_cached_or_new()
 
         if dummy:
             # dummy==True deactivate all methods