From 0e5b8d62a6624cf659984955ad298b6a45874482 Mon Sep 17 00:00:00 2001
From: Elliott Sales de Andrade <quantum.analyst@gmail.com>
Date: Thu, 7 Nov 2019 20:32:09 -0500
Subject: [PATCH] Backport PR #15626: Note minimum supported version for
 fontconfig.

---
 INSTALL.rst                    | 4 +++-
 lib/matplotlib/font_manager.py | 4 ++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/INSTALL.rst b/INSTALL.rst
index 3d64becf80f5..c508de43edc2 100644
--- a/INSTALL.rst
+++ b/INSTALL.rst
@@ -164,7 +164,9 @@ etc., you can install the following:
 * `Pillow <https://pillow.readthedocs.io/en/latest/>`_ (>= 3.4): for a larger
   selection of image file formats: JPEG, BMP, and TIFF image files;
 * `LaTeX <https://miktex.org/>`_ and `GhostScript (>=9.0)
-  <https://ghostscript.com/download/>`_ : for rendering text with LaTeX.
+  <https://ghostscript.com/download/>`_ : for rendering text with LaTeX;
+* `fontconfig <https://www.fontconfig.org>`_ (>= 2.7): for detection of system
+  fonts on Linux.
 
 .. note::
 
diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
index 0f752166435c..df9fa6e6a6e2 100644
--- a/lib/matplotlib/font_manager.py
+++ b/lib/matplotlib/font_manager.py
@@ -273,6 +273,10 @@ def _call_fc_list():
         'This may take a moment.'))
     timer.start()
     try:
+        if b'--format' not in subprocess.check_output(['fc-list', '--help']):
+            _log.warning(  # fontconfig 2.7 implemented --format.
+                'Matplotlib needs fontconfig>=2.7 to query system fonts.')
+            return []
         out = subprocess.check_output(['fc-list', '--format=%{file}\\n'])
     except (OSError, subprocess.CalledProcessError):
         return []