configure

#!/bin/sh

# A handwritten ./configure script, because I kind of hate autotools.
# Update (2023): Autotools=still awful. But writing this was a mistake.
# © 2020–2023 Eddie Antonio Santos <hello@eddieantonio.ca>

set -e

################################# CONSTANTS ##################################

version="$(<VERSION tr -d '\r')"


################################# VARIABLES ##################################

# A series of #define lines to write in src/cimg_config.h
defines=""
# A space-separated list of linker flags to link with required libraries
libs=""
# A space-separated list of compiler flags to configure include paths
includes=""
# The program used for pandoc
pandoc=""
# What flag to use to compile using C++11 features.
cxxstd=""


#################################### MAIN ####################################

main() {
  ############################ Check for features ############################
  require_system_header sys/ioctl.h
  require_system_header sys/time.h
  require_system_header term.h
  require_system_header sysexits.h

  # Figure out how to compile C++ 11 code
  if use_cxxflag -std=c++11 ; then
    cxxstd="-std=c++11"
  elif use_cxxflag -std=c++0x ; then
    cxxstd="-std=c++0x"
  else
    error "unable to find a C++11 compiler"
  fi

  # Link with -lcurses (required)
  if link_lib_against_test_program tigetnum ncurses ; then
    libs="${libs} -lncurses"
  elif link_lib_against_test_program tigetnum curses ; then
    libs="${libs} -lcurses"
  else
    error "ncurses is required for compilation"
  fi

  # Link with -lpng (optional)
  if link_lib_against_test_program_using_pkgconfig png_create_info_struct png ; then
    defines="${defines}#define cimg_use_png 1${NEWLINE}"
    extend_libs_and_includes_using_pkgconfig png
  fi

  # Link with -ljpg (optional)
  if link_lib_against_test_program_using_pkgconfig jpeg_set_defaults jpeg ; then
    defines="${defines}#define cimg_use_jpeg 1${NEWLINE}"
    extend_libs_and_includes_using_pkgconfig jpeg
  fi

  # Check if pandoc is installed (optional)
  if check_for_program pandoc ; then
    pandoc="pandoc"
  else
    echo "warning: ignoring requirement for pandoc..." 1>&2
    pandoc="true"
  fi

  ############################## Generate files ##############################
  generate_file config.mk <<EOF
# AUTOGENERATED FILE! DO NOT MODIFY!
PACKAGE_VERSION = ${version}
PANDOC = ${pandoc}
LIBS = ${libs}
INCLUDE_FLAGS = ${includes}
CXXSTD = ${cxxstd}
EOF

  generate_file src/config.h <<EOF
/* AUTOGENERATED FILE; DO NOT MODIFY */
#ifndef CONFIG_H
#define CONFIG_H
#define PACKAGE_VERSION "${version}"
#endif /* CONFIG_H */
EOF

  generate_file src/cimg_config.h <<EOF
/* AUTOGENERATED FILE; DO NOT MODIFY */
#ifndef CIMG_CONFIG_H
#define CIMG_CONFIG_H
/* IMPORTANT! Include this BEFORE CImg.h. */
${defines}
#endif /* CIMG_CONFIG_H */
EOF
}


############################# INTERNAL CONSTANTS #############################

# see: man 3 sysexits
EX_UNAVAILABLE=69
# (nice)

NEWLINE="$(printf '\n ')" && NEWLINE="${NEWLINE% }"

# Use the default C and C++ compilers
CC="${CC:-gcc}"
CXX="${CXX:-c++}"
TMPDIR="${TMPDIR:-/tmp}"

# Colors
BOLDRED="$(tput setaf 1 || :)$(tput bold || :)"
RESET="$(tput sgr0 || :)"


############################## HELPER FUNCTIONS ##############################

require_system_header() {
  header="$1"
  if ! compile_with_header "$header" ; then
    error "failed to find required header: $header"
  fi
}

use_cxxflag() {
  flag="$1"
  printf 'checking to compile C++ with %s...' "${flag}"

  compile_test_cxx_program "${flag}" <<EOF
int main(void) {
  void *p = nullptr;
  return p != 0;
}
EOF
}

# Create a test program that uses a library function and link against that
# library. Returns zero on if the library was linked succesfully, non-zero
# otherwise.
link_lib_against_test_program() {
  funcname=$1
  lib=$2

  printf 'checking to link with lib%s [using %s()]... ' "$lib" "$funcname"
  compile_test_program -l"${lib}" <<EOF
char ${funcname}(void);

int main(void) {
  return ${funcname}();
}
EOF
}

# Create a test program that uses a library function and link against that
# library. Returns zero on if the library was linked succesfully, non-zero
# otherwise.
link_lib_against_test_program_using_pkgconfig() {
  funcname=$1
  lib=$2

  printf 'checking to link with lib%s using pkg-config [using %s()]... ' "$lib" "$funcname"
  # Contrary to best practices, pkg-config actually depends on its output
  # being broken by spaces to create multiple arguments from one invocation,
  # so ignore the lint:
  # shellcheck disable=SC2046
  compile_test_program $(pkg-config --cflags --libs "lib${lib}") <<EOF
char ${funcname}(void);

int main(void) {
  return ${funcname}();
}
EOF
}

# Add the appropriate flags for the given library using pkg-config(1)
extend_libs_and_includes_using_pkgconfig() {
  lib=$1

  libs="${libs} $(pkg-config --libs "lib${lib}")"
  includes="${includes} $(pkg-config --cflags "lib${lib}")"
}

# Check if the program is on the path.
check_for_program() {
  program="$1"

  printf 'checking for %s... ' "${program}"
  if which "${program}" >/dev/null 2>&1 ; then
    echo "${program}"
    return 0
  else
    echo "no"
    return 1
  fi
}

# Creates a file with contents from stdin.
generate_file() {
  filename="$1"
  echo "creating $filename"
  cat > "$filename"
}

# Print an error message and quit
error() {
  echo "$0: ${BOLDRED}error${RESET}:" "$@" 1>&2
  exit ${EX_UNAVAILABLE}
}

# Create a test program that includes the given system header.
compile_with_header() {
  header=$1

  printf 'checking for %s... ' "$header"
  # We include <Availability.h> on Apple to workaround issue an issue with
  # term.h on newer macOS.
  # See: https://github.com/eddieantonio/imgcat/issues/51
  compile_test_program -c <<EOF
#ifdef __APPLE__
#include <Availability.h>
#endif

#include <${header}>
EOF
}

# Compiles a test C program given on stdin.
# Any arguments are passed to the compiler.
compile_test_program() {
  filename="${TMPDIR}/conftest.$$.c"

  cat > "${filename}"
  if "${CC}" -o /dev/null "${filename}" "$@" ; then
    echo "yes"
    return 0
  else
    echo "no"
    return 1
  fi
}

# Compiles a test C++ program given on stdin.
# Any arguments are passed to the compiler.
compile_test_cxx_program() {
  filename="${TMPDIR}/conftest.$$.cc"

  cat > "${filename}"
  if "${COMPILER:=${CC}}" -o /dev/null "${filename}" "$@" ; then
    echo "yes"
    return 0
  else
    echo "no"
    return 1
  fi
}


############################### Run configure! ###############################

main