[docwriter] Drop support for Python < 3.5.

Python versions < 3.5 have reached end-of-life and as such, no
security or bug fixes will be provided for those versions.  See

  https://devguide.python.org/#status-of-python-branches

for more information.

* Jamfile (RefDoc): Add `site' parameter.

* builds/detect.mk (std_setup): Update Python version requirement.

* builds/freetype.mk (refdoc-venv): Use pip as `python -m pip'.

* builds/unix/ax_compare_version.m4,
builds/unix/ax_prog_python_version.m4: Macros to detect Python
version.  New files.

* builds/unix/configure.raw: Check for Python >= 3.5 and remove
check for `pip'.

* docs/CHANGES, docs/INSTALL.GNU, docs/README: Updated.

10 files changed, 302 insertions, 28 deletions

diff --git a/ChangeLog b/ChangeLog
index 471b5c824..aa8eb98d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,29 @@
+2020-03-21  Nikhil Ramakrishnan  <ramakrishnan.nikhil@gmail.com>
+
+	[docwriter] Drop support for Python < 3.5.
+
+	Python versions < 3.5 have reached end-of-life and as such, no
+	security or bug fixes will be provided for those versions.  See
+
+	  https://devguide.python.org/#status-of-python-branches
+	
+	for more information.
+
+	* Jamfile (RefDoc): Add `site' parameter.
+
+	* builds/detect.mk (std_setup): Update Python version requirement.
+
+	* builds/freetype.mk (refdoc-venv): Use pip as `python -m pip'.
+
+	* builds/unix/ax_compare_version.m4,
+	builds/unix/ax_prog_python_version.m4: Macros to detect Python
+	version.  New files.
+
+	* builds/unix/configure.raw: Check for Python >= 3.5 and remove
+	check for `pip'.
+
+	* docs/CHANGES, docs/INSTALL.GNU, docs/README: Updated.
+
 2020-03-02  Moazin Khatti  <moazinkhatri@gmail.com>
 
 	[gzip] Support `gzip' encoded header conditionally.
diff --git a/Jamfile b/Jamfile
index b2ee7eece..660cfc427 100644
--- a/Jamfile
+++ b/Jamfile
@@ -208,13 +208,14 @@ rule RefDoc
 
 actions RefDoc
 {
-  python -m docwriter
-         --prefix=ft2
-         --title=FreeType-2.10.1
-         --output=$(DOC_DIR)
-         $(FT2_INCLUDE)/freetype/*.h
-         $(FT2_INCLUDE)/freetype/config/*.h
-         $(FT2_INCLUDE)/freetype/cache/*.h
+  python3 -m docwriter
+          --prefix=ft2
+          --title=FreeType-2.10.1
+          --site=reference
+          --output=$(DOC_DIR)
+          $(FT2_INCLUDE)/freetype/*.h
+          $(FT2_INCLUDE)/freetype/config/*.h
+          $(FT2_INCLUDE)/freetype/cache/*.h
 }
 
 RefDoc  refdoc ;
diff --git a/builds/detect.mk b/builds/detect.mk
index c6c2beb6c..94627fc05 100644
--- a/builds/detect.mk
+++ b/builds/detect.mk
@@ -120,7 +120,7 @@ std_setup:
 	$(info `$(CONFIG_MK)' from this directory then read the INSTALL file for help.)
 	$(info )
 	$(info Otherwise, simply type `$(MAKE)' again to build the library,)
-	$(info or `$(MAKE) refdoc' to build the API reference (this needs python >= 2.6).)
+	$(info or `$(MAKE) refdoc' to build the API reference (this needs Python >= 3.5).)
 	$(info )
 	@$(COPY) $(subst /,$(SEP),$(CONFIG_RULES) $(CONFIG_MK))
 
diff --git a/builds/freetype.mk b/builds/freetype.mk
index a0d7c5803..0df7d4082 100644
--- a/builds/freetype.mk
+++ b/builds/freetype.mk
@@ -290,11 +290,8 @@ objects: $(OBJECTS_LIST)
 library: $(PROJECT_LIBRARY)
 
 # Run `docwriter' in the current Python environment.
-# Option `-B' disables generation of .pyc files (available since python 2.6)
 #
-
 PYTHON ?= python
-PIP    ?= pip
 
 refdoc:
 	@echo Running docwriter...
@@ -319,13 +316,12 @@ refdoc:
 VENV_NAME  := env
 VENV_DIR   := $(DOC_DIR)$(SEP)$(VENV_NAME)
 ENV_PYTHON := $(VENV_DIR)$(SEP)$(BIN)$(SEP)$(PYTHON)
-ENV_PIP    := $(VENV_DIR)$(SEP)$(BIN)$(SEP)$(PIP)
 
 refdoc-venv:
 	@echo Setting up virtualenv for Python...
 	virtualenv --python=$(PYTHON) $(VENV_DIR)
 	@echo Installing docwriter...
-	$(ENV_PIP) install docwriter
+	$(ENV_PYTHON) -m pip install docwriter
 	@echo Running docwriter...
 	$(ENV_PYTHON) -m docwriter \
                       --prefix=ft2 \
diff --git a/builds/unix/ax_compare_version.m4 b/builds/unix/ax_compare_version.m4
new file mode 100644
index 000000000..ffb4997e8
--- /dev/null
+++ b/builds/unix/ax_compare_version.m4
@@ -0,0 +1,177 @@
+# ===========================================================================
+#    https://www.gnu.org/software/autoconf-archive/ax_compare_version.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_COMPARE_VERSION(VERSION_A, OP, VERSION_B, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
+#
+# DESCRIPTION
+#
+#   This macro compares two version strings. Due to the various number of
+#   minor-version numbers that can exist, and the fact that string
+#   comparisons are not compatible with numeric comparisons, this is not
+#   necessarily trivial to do in a autoconf script. This macro makes doing
+#   these comparisons easy.
+#
+#   The six basic comparisons are available, as well as checking equality
+#   limited to a certain number of minor-version levels.
+#
+#   The operator OP determines what type of comparison to do, and can be one
+#   of:
+#
+#    eq  - equal (test A == B)
+#    ne  - not equal (test A != B)
+#    le  - less than or equal (test A <= B)
+#    ge  - greater than or equal (test A >= B)
+#    lt  - less than (test A < B)
+#    gt  - greater than (test A > B)
+#
+#   Additionally, the eq and ne operator can have a number after it to limit
+#   the test to that number of minor versions.
+#
+#    eq0 - equal up to the length of the shorter version
+#    ne0 - not equal up to the length of the shorter version
+#    eqN - equal up to N sub-version levels
+#    neN - not equal up to N sub-version levels
+#
+#   When the condition is true, shell commands ACTION-IF-TRUE are run,
+#   otherwise shell commands ACTION-IF-FALSE are run. The environment
+#   variable 'ax_compare_version' is always set to either 'true' or 'false'
+#   as well.
+#
+#   Examples:
+#
+#     AX_COMPARE_VERSION([3.15.7],[lt],[3.15.8])
+#     AX_COMPARE_VERSION([3.15],[lt],[3.15.8])
+#
+#   would both be true.
+#
+#     AX_COMPARE_VERSION([3.15.7],[eq],[3.15.8])
+#     AX_COMPARE_VERSION([3.15],[gt],[3.15.8])
+#
+#   would both be false.
+#
+#     AX_COMPARE_VERSION([3.15.7],[eq2],[3.15.8])
+#
+#   would be true because it is only comparing two minor versions.
+#
+#     AX_COMPARE_VERSION([3.15.7],[eq0],[3.15])
+#
+#   would be true because it is only comparing the lesser number of minor
+#   versions of the two values.
+#
+#   Note: The characters that separate the version numbers do not matter. An
+#   empty string is the same as version 0. OP is evaluated by autoconf, not
+#   configure, so must be a string, not a variable.
+#
+#   The author would like to acknowledge Guido Draheim whose advice about
+#   the m4_case and m4_ifvaln functions make this macro only include the
+#   portions necessary to perform the specific comparison specified by the
+#   OP argument in the final configure script.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Tim Toolan <toolan@ele.uri.edu>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 13
+
+dnl #########################################################################
+AC_DEFUN([AX_COMPARE_VERSION], [
+  AC_REQUIRE([AC_PROG_AWK])
+
+  # Used to indicate true or false condition
+  ax_compare_version=false
+
+  # Convert the two version strings to be compared into a format that
+  # allows a simple string comparison.  The end result is that a version
+  # string of the form 1.12.5-r617 will be converted to the form
+  # 0001001200050617.  In other words, each number is zero padded to four
+  # digits, and non digits are removed.
+  AS_VAR_PUSHDEF([A],[ax_compare_version_A])
+  A=`echo "$1" | sed -e 's/\([[0-9]]*\)/Z\1Z/g' \
+                     -e 's/Z\([[0-9]]\)Z/Z0\1Z/g' \
+                     -e 's/Z\([[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+                     -e 's/Z\([[0-9]][[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+                     -e 's/[[^0-9]]//g'`
+
+  AS_VAR_PUSHDEF([B],[ax_compare_version_B])
+  B=`echo "$3" | sed -e 's/\([[0-9]]*\)/Z\1Z/g' \
+                     -e 's/Z\([[0-9]]\)Z/Z0\1Z/g' \
+                     -e 's/Z\([[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+                     -e 's/Z\([[0-9]][[0-9]][[0-9]]\)Z/Z0\1Z/g' \
+                     -e 's/[[^0-9]]//g'`
+
+  dnl # In the case of le, ge, lt, and gt, the strings are sorted as necessary
+  dnl # then the first line is used to determine if the condition is true.
+  dnl # The sed right after the echo is to remove any indented white space.
+  m4_case(m4_tolower($2),
+  [lt],[
+    ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort -r | sed "s/x${A}/false/;s/x${B}/true/;1q"`
+  ],
+  [gt],[
+    ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort | sed "s/x${A}/false/;s/x${B}/true/;1q"`
+  ],
+  [le],[
+    ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort | sed "s/x${A}/true/;s/x${B}/false/;1q"`
+  ],
+  [ge],[
+    ax_compare_version=`echo "x$A
+x$B" | sed 's/^ *//' | sort -r | sed "s/x${A}/true/;s/x${B}/false/;1q"`
+  ],[
+    dnl Split the operator from the subversion count if present.
+    m4_bmatch(m4_substr($2,2),
+    [0],[
+      # A count of zero means use the length of the shorter version.
+      # Determine the number of characters in A and B.
+      ax_compare_version_len_A=`echo "$A" | $AWK '{print(length)}'`
+      ax_compare_version_len_B=`echo "$B" | $AWK '{print(length)}'`
+
+      # Set A to no more than B's length and B to no more than A's length.
+      A=`echo "$A" | sed "s/\(.\{$ax_compare_version_len_B\}\).*/\1/"`
+      B=`echo "$B" | sed "s/\(.\{$ax_compare_version_len_A\}\).*/\1/"`
+    ],
+    [[0-9]+],[
+      # A count greater than zero means use only that many subversions
+      A=`echo "$A" | sed "s/\(\([[0-9]]\{4\}\)\{m4_substr($2,2)\}\).*/\1/"`
+      B=`echo "$B" | sed "s/\(\([[0-9]]\{4\}\)\{m4_substr($2,2)\}\).*/\1/"`
+    ],
+    [.+],[
+      AC_WARNING(
+        [invalid OP numeric parameter: $2])
+    ],[])
+
+    # Pad zeros at end of numbers to make same length.
+    ax_compare_version_tmp_A="$A`echo $B | sed 's/./0/g'`"
+    B="$B`echo $A | sed 's/./0/g'`"
+    A="$ax_compare_version_tmp_A"
+
+    # Check for equality or inequality as necessary.
+    m4_case(m4_tolower(m4_substr($2,0,2)),
+    [eq],[
+      test "x$A" = "x$B" && ax_compare_version=true
+    ],
+    [ne],[
+      test "x$A" != "x$B" && ax_compare_version=true
+    ],[
+      AC_WARNING([invalid OP parameter: $2])
+    ])
+  ])
+
+  AS_VAR_POPDEF([A])dnl
+  AS_VAR_POPDEF([B])dnl
+
+  dnl # Execute ACTION-IF-TRUE / ACTION-IF-FALSE.
+  if test "$ax_compare_version" = "true" ; then
+    m4_ifvaln([$4],[$4],[:])dnl
+    m4_ifvaln([$5],[else $5])dnl
+  fi
+]) dnl AX_COMPARE_VERSION
diff --git a/builds/unix/ax_prog_python_version.m4 b/builds/unix/ax_prog_python_version.m4
new file mode 100644
index 000000000..dbc3dbf1d
--- /dev/null
+++ b/builds/unix/ax_prog_python_version.m4
@@ -0,0 +1,66 @@
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_prog_python_version.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PROG_PYTHON_VERSION([VERSION],[ACTION-IF-TRUE],[ACTION-IF-FALSE])
+#
+# DESCRIPTION
+#
+#   Makes sure that python supports the version indicated. If true the shell
+#   commands in ACTION-IF-TRUE are executed. If not the shell commands in
+#   ACTION-IF-FALSE are run. Note if $PYTHON is not set (for example by
+#   running AC_CHECK_PROG or AC_PATH_PROG) the macro will fail.
+#
+#   Example:
+#
+#     AC_PATH_PROG([PYTHON],[python])
+#     AX_PROG_PYTHON_VERSION([2.4.4],[ ... ],[ ... ])
+#
+#   This will check to make sure that the python you have supports at least
+#   version 2.4.4.
+#
+#   NOTE: This macro uses the $PYTHON variable to perform the check.
+#   AX_WITH_PYTHON can be used to set that variable prior to running this
+#   macro. The $PYTHON_VERSION variable will be valorized with the detected
+#   version.
+#
+# LICENSE
+#
+#   Copyright (c) 2009 Francesco Salvestrini <salvestrini@users.sourceforge.net>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 12
+
+AC_DEFUN([AX_PROG_PYTHON_VERSION],[
+    AC_REQUIRE([AC_PROG_SED])
+    AC_REQUIRE([AC_PROG_GREP])
+
+    AS_IF([test -n "$PYTHON"],[
+        ax_python_version="$1"
+
+        AC_MSG_CHECKING([for python version])
+        changequote(<<,>>)
+        python_version=`$PYTHON -V 2>&1 | $GREP "^Python " | $SED -e 's/^.* \([0-9]*\.[0-9]*\.[0-9]*\)/\1/'`
+        changequote([,])
+        AC_MSG_RESULT($python_version)
+
+	AC_SUBST([PYTHON_VERSION],[$python_version])
+
+        AX_COMPARE_VERSION([$ax_python_version],[le],[$python_version],[
+	    :
+            $2
+        ],[
+	    :
+            $3
+        ])
+    ],[
+        AC_MSG_WARN([could not find the python interpreter])
+        $3
+    ])
+])
diff --git a/builds/unix/configure.raw b/builds/unix/configure.raw
index 2b07f3f52..5ab549c9c 100644
--- a/builds/unix/configure.raw
+++ b/builds/unix/configure.raw
@@ -1012,16 +1012,20 @@ case "$CFLAGS" in
     ;;
 esac
 
-# Check for python and docwriter
+# Check for Python and docwriter
 
-AC_CHECK_PROGS([PYTHON], [python3 python2 python], [missing])
+have_py3=no
 have_docwriter=no
+PIP=pip
+
+AC_CHECK_PROGS([PYTHON], [python3 python], [missing])
 if test "x$PYTHON" != "xmissing"; then
-  AC_CHECK_PROGS([PIP], [pip3 pip2 pip], [missing])
+  AX_PROG_PYTHON_VERSION([3.5], [have_py3=yes], [])
 
-  if test "x$PIP" != "xmissing"; then
+  if test "x$have_py3" = "xyes"; then
+    PIP="$PYTHON -m $PIP"
     AC_MSG_CHECKING([for \`docwriter' Python module])
-    $PIP show -q docwriter
+    $PYTHON -m docwriter -h > /dev/null 2>&1
     if test "x$?" = "x0"; then
       have_docwriter=yes
       AC_MSG_RESULT([yes])
@@ -1191,9 +1195,9 @@ Library configuration:
 if test $have_docwriter = no; then
   AC_MSG_NOTICE([
   Warning: \`make refdoc' will fail since pip package \`docwriter' is not
-  installed.  To install, run \`$PIP install docwriter', or to use a python
+  installed.  To install, run \`$PIP install docwriter', or to use a Python
   virtual environment, run \`make refdoc-venv' (requires pip package
-  \`virtualenv').
+  \`virtualenv'). These operations require Python >= 3.5.
   ])
 fi
 
diff --git a/docs/CHANGES b/docs/CHANGES
index eb3bb46c7..9704fca59 100644
--- a/docs/CHANGES
+++ b/docs/CHANGES
@@ -12,6 +12,10 @@ CHANGES BETWEEN 2.10.1 and 2.10.2
   - Function  `FT_Get_Var_Axis_Flags' returned random data for  Type 1
     MM fonts.
 
+  - Drop  support  for Python 2 in Freetype's API reference  generator
+    `docwriter'  (Python >= 3.5 is required for targets  `make refdoc'
+    and `make refdoc-venv').
+
 
 ======================================================================
 
diff --git a/docs/INSTALL.GNU b/docs/INSTALL.GNU
index d61e38757..8fdbb825e 100644
--- a/docs/INSTALL.GNU
+++ b/docs/INSTALL.GNU
@@ -63,7 +63,7 @@ instructions in the file `INSTALL.UNIX' instead.
 
       Otherwise, simply type 'make' again to build the library
       or 'make refdoc' to build the API reference (the latter needs
-      python).
+      Python >= 3.5).
       =============================================================
 
 
diff --git a/docs/README b/docs/README
index 3ffcfc080..f82382d45 100644
--- a/docs/README
+++ b/docs/README
@@ -1,6 +1,6 @@
 After saying `make refdoc' or `make refdoc-venv' the `site/' directory
-contains the FreeType API reference.  You need python and pip to make this
-target.
+contains the FreeType API reference.  You need Python >= 3.5 and pip to make
+this target.
 
 There are two ways to generate the documentation:
 
@@ -13,7 +13,7 @@ There are two ways to generate the documentation:
 
 2. Using `make refdoc-venv' (requires internet access):
 
-    - Ensure `python', `pip' and python package `virtualenv' are available.
+    - Ensure `python', `pip' and Python package `virtualenv' are available.
     - Make target with `make refdoc-venv'.
     - This may or may not require internet access every time depending on
     pip and system caching.
@@ -25,11 +25,11 @@ Some troubleshooting tips:
 * Regularly run `pip install --upgrade docwriter' to check for updates which
 may include bug fixes.
 
-* Ensure that `docwriter' is installed in the same python target that
-`make refdoc' uses (python3/python2/python).
+* `Docwriter' does not support Python 2.  Ensure that Python >= 3.5 is
+installed and available as `python3'/`python'.
 
-* `pip' and `python' may point to different versions of Python.  Check using
-`python --version' and `pip --version'.
+* Ensure that `docwriter' is installed in the same Python target that
+`make refdoc' uses (python3/python).
 
 * If none of this works, send a mail to `freetype-devel@nongnu.org' or file
 an issue at `https://github.com/freetype/docwriter/issues'.