matplotlib · jklymak · Nov 11, 2018 · Oct 30, 2018 · Oct 30, 2018 · Oct 30, 2018
diff --git a/doc/api/next_api_changes/2018-10-30-rcparams-pgf.preamble-full-LaTeX-support.rst b/doc/api/next_api_changes/2018-10-30-rcparams-pgf.preamble-full-LaTeX-support.rst
@@ -0,0 +1,11 @@
+Allow "real" LaTeX code for ``pgf.preamble`` and ``text.latex.preamble`` in matplotlib rc file
+``````````````````````````````````````````````````````````````````````````````````````````````
+
+Previously, the rc file keys ``pgf.preamble`` and ``text.latex.preamble`` were parsed using commmas as separators. This would break valid LaTeX code, such as::
+
+\usepackage[protrusion=true, expansion=false]{microtype}
+
+The parsing has been modified to pass the complete line to the LaTeX system,
+keeping all commas.
+
+Passing a list of strings from within a Python script still works as it used to.
diff --git a/doc/users/next_whats_new/2018-10-30-rcparams-pgf.preamble-full-LaTeX-support.rst b/doc/users/next_whats_new/2018-10-30-rcparams-pgf.preamble-full-LaTeX-support.rst
@@ -0,0 +1,11 @@
+Allow "real" LaTeX code for ``pgf.preamble`` and ``text.latex.preamble`` in matplotlib rc file
+``````````````````````````````````````````````````````````````````````````````````````````````
+
+Previously, the rc file keys ``pgf.preamble`` and ``text.latex.preamble`` were parsed using commmas as separators. This would break valid LaTeX code, such as::
+
+\usepackage[protrusion=true, expansion=false]{microtype}
+
+The parsing has been modified to pass the complete line to the LaTeX system,
+keeping all commas.
+
+Passing a list of strings from within a Python script still works as it used to.
diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
@@ -59,7 +59,7 @@ def get_fontspec():
 
 def get_preamble():
     """Get LaTeX preamble from rc."""
-    return "\n".join(rcParams["pgf.preamble"])
+    return rcParams["pgf.preamble"]
 
 ###############################################################################
 

diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -175,6 +175,20 @@ def validate_string_or_None(s):
         raise ValueError('Could not convert "%s" to string' % s)
 
 
+def _validate_stringlist_or_string(s):
+    """convert s to string or raise"""
+    if s is None or s == 'None':
+        return ""
+    try:
+        if isinstance(s, str):
+            return s
+        if isinstance(s, Iterable):
+            return '\n'.join([str(i) for i in s])
+        raise ValueError()
+    except ValueError:
+        raise ValueError('Could not convert "%s" to string' % s)
+
+
 def validate_axisbelow(s):
     try:
         return validate_bool(s)
@@ -1115,7 +1129,7 @@ def _validate_linestyle(ls):
     'text.color':          ['black', validate_color],
     'text.usetex':         [False, validate_bool],
     'text.latex.unicode':  [True, validate_bool],
-    'text.latex.preamble': [[], validate_stringlist],
+    'text.latex.preamble': ['', _validate_stringlist_or_string],
     'text.latex.preview':  [False, validate_bool],
     'text.dvipnghack':     [None, validate_bool_maybe_none],
     'text.hinting':        ['auto', validate_hinting],
@@ -1391,7 +1405,7 @@ def _validate_linestyle(ls):
     # use matplotlib rc settings for font configuration
     'pgf.rcfonts':   [True, validate_bool],
     # provide a custom preamble for the latex process
-    'pgf.preamble':  [[], validate_stringlist],
+    'pgf.preamble':  ['', _validate_stringlist_or_string],
 
     # write raster image data directly into the svg file
     'svg.image_inline':     [True, validate_bool],

diff --git a/matplotlibrc.template b/matplotlibrc.template
@@ -229,14 +229,18 @@
 #text.latex.preamble :      ## IMPROPER USE OF THIS FEATURE WILL LEAD TO LATEX FAILURES
                             ## AND IS THEREFORE UNSUPPORTED. PLEASE DO NOT ASK FOR HELP
                             ## IF THIS FEATURE DOES NOT DO WHAT YOU EXPECT IT TO.
-                            ## preamble is a comma separated list of LaTeX statements
-                            ## that are included in the LaTeX document preamble.
-                            ## An example:
-                            ## text.latex.preamble : \usepackage{bm},\usepackage{euler}
+                            ## text.latex.preamble is a single line of LaTeX code that
+                            ## will be passed on to the LaTeX system. It may contain
+                            ## any code that is valid for the LaTeX "preamble", i.e.
+                            ## between the "\documentclass" and "\begin{document}"
+                            ## statements.
+                            ## Note that it has to be put on a single line, which may
+                            ## become quite long.
                             ## The following packages are always loaded with usetex, so
                             ## beware of package collisions: color, geometry, graphicx,
-                            ## type1cm, textcomp. Adobe Postscript (PSSNFS) font packages
-                            ## may also be loaded, depending on your font settings
+                            ## type1cm, textcomp.
+                            ## Adobe Postscript (PSSNFS) font packages may also be
+                            ## loaded, depending on your font settings.
 #text.latex.preview : False
 
 #text.hinting : auto   ## May be one of the following:
@@ -567,7 +571,7 @@
                                ## instead of uuid4
 ### pgf parameter
 #pgf.rcfonts : True
-#pgf.preamble :
+#pgf.preamble :            ## see text.latex.preamble for documentation
 #pgf.texsystem : xelatex
 
 ### docstring params