Improved rendering of equations in HTML documentation generated by Doxygen. Make use of MathJax 2.x if found

cmake/Modules/FindMATHJAX2.cmake

@@ -0,0 +1,60 @@
+# Copyright (C) 2011-2020  (see AUTHORS file for a list of contributors)
+#
+# GNSS-SDR is a software-defined Global Navigation Satellite Systems receiver
+#
+# This file is part of GNSS-SDR.
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+#
+# Find MathJax package (version 2).
+#
+# A hint can be provided by defining MATHJAX2_ROOT
+# (will succeed if ${MATHJAX2_ROOT}/MathJax.js is found).
+#
+# Alternatively, a path can be provided in MATHJAX2_USE_ROOT
+# so that ${MATHJAX2_USE_ROOT}/MathJax.js is used without
+# checking its existence.
+# This path could be a URL, an absolute local path or
+# a path relative to the generated HTML folder.
+#
+# Note that version 2 and 3 are incompatible
+# and doxygen requires version 2.
+# See: https://github.com/doxygen/doxygen/issues/7346
+#
+# Defined variables:
+#  - MATHJAX2_FOUND     - True if MathJax found
+#  - MATHJAX2_JS_PATH   - Path to MathJax.js file
+#  - MATHJAX2_PATH      - Path to the MathJax root directory
+
+
+if(CMAKE_VERSION VERSION_LESS 3.11)
+    if(__INCLUDED_MATHJAX2)
+        return()
+    endif()
+    set(__INCLUDED_MATHJAX2 TRUE)
+else()
+    include_guard()
+endif()
+
+if(DEFINED MATHJAX2_USE_ROOT)
+    set(MATHJAX2_FOUND TRUE)
+    set(MATHJAX2_PATH "${MATHJAX2_USE_ROOT}/")
+    set(MATHJAX2_JS_PATH "${MATHJAX2_USE_ROOT}/MathJax.js")
+else()
+    find_file(MATHJAX2_JS_PATH
+        NAMES
+            MathJax.js
+        PATHS
+            "${MATHJAX2_ROOT}"
+            /usr/share/mathjax2/
+            /usr/share/javascript/mathjax/
+            /usr/local/share/javascript/mathjax/
+    )
+
+    get_filename_component(MATHJAX2_PATH ${MATHJAX2_JS_PATH} DIRECTORY)
+
+    find_package_handle_standard_args(MATHJAX2 DEFAULT_MSG MATHJAX2_JS_PATH)
+endif()
+
+mark_as_advanced(MATHJAX2_JS_PATH)