# CMakeLists.txt - CMake lists for libpng
#
# Copyright (c) 2018-2025 Cosmin Truta
# Copyright (c) 2007-2018 Glenn Randers-Pehrson
# Originally written by Christian Ehrlicher, 2007
#
# Use, modification and distribution are subject to
# the same licensing terms and conditions as libpng.
# Please see the copyright notice in png.h or visit
# http://libpng.org/pub/png/src/libpng-LICENSE.txt
#
# For copyright and licensing purposes, please see
# the accompanying file scripts/cmake/AUTHORS.md
#
# SPDX-License-Identifier: libpng-2.0

cmake_minimum_required(VERSION 3.14...4.2)

set(PNGLIB_MAJOR 2)
set(PNGLIB_MINOR 0)
set(PNGLIB_REVISION 0)
#set(PNGLIB_SUBREVISION 0)
set(PNGLIB_SUBREVISION "git")
set(PNGLIB_VERSION ${PNGLIB_MAJOR}.${PNGLIB_MINOR}.${PNGLIB_REVISION})
set(PNGLIB_ABI_VERSION ${PNGLIB_MAJOR})
set(PNGLIB_SHARED_VERSION ${PNGLIB_VERSION}.${PNGLIB_SUBREVISION})

project(libpng
        VERSION ${PNGLIB_VERSION}
        LANGUAGES C)

include(CheckCSourceCompiles)
include(CheckLibraryExists)
include(GNUInstallDirs)

# Allow the users to specify an application-specific API prefix for libpng
# vendoring purposes. A standard libpng build should have no such prefix.
set(PNG_PREFIX
    ""
    CACHE STRING "Prefix to prepend to the API function names")

# Allow the users to override the postfix appended to debug library file names.
# Previously, we used to set CMAKE_DEBUG_POSTFIX globally. That variable should
# not be cached, however, because doing so would affect all projects processed
# after libpng, in unexpected and undesirable ways.
set(PNG_DEBUG_POSTFIX
    "d"
    CACHE STRING "Postfix to append to library file names under the Debug configuration")

# Allow the users to import their own extra configuration settings.
# Those settings can be either passed via DFA_XTRA if they are in DFA form
# (such as "pngusr.dfa"), or via PNG_LIBCONF_HEADER if they are in prebuilt
# header file form (such as "pnglibconf.h.prebuilt"), but not both.
# For platforms such as Android or iOS, or in certain cross-platform build
# scenarios, having a valid PNG_LIBCONF_HEADER is mandatory.
set(DFA_XTRA
    ""
    CACHE FILEPATH "DFA file containing customized build configuration settings for libpng")
set(PNG_LIBCONF_HEADER
    ""
    CACHE FILEPATH "C header file containing customized build configuration settings for libpng")
set(PNG_LIBCONF_HEADER_PREBUILT "${CMAKE_CURRENT_SOURCE_DIR}/pnglibconf.h.prebuilt")
if(ANDROID OR IOS)
  set(PNG_LIBCONF_HEADER "${PNG_LIBCONF_HEADER_PREBUILT}")
endif()
if((NOT DFA_XTRA STREQUAL "") AND (NOT PNG_LIBCONF_HEADER STREQUAL ""))
  message(SEND_ERROR "The options DFA_XTRA=\"${DFA_XTRA}\" "
                     "and PNG_LIBCONF_HEADER=\"${PNG_LIBCONF_HEADER}\" "
                     "are mutually exclusive")
endif()

# Allow the users to switch on/off various library build types.
option(PNG_SHARED "Build libpng as a shared library" ON)
option(PNG_STATIC "Build libpng as a static library" ON)
if(APPLE)
  option(PNG_FRAMEWORK "Build libpng as a framework bundle" ON)
else()
  option(PNG_FRAMEWORK "Build libpng as a framework bundle (not available on this platform)" OFF)
endif()
if(NOT APPLE AND PNG_FRAMEWORK)
  message(SEND_ERROR "The option PNG_FRAMEWORK should not be set on this platform")
endif()

# Allow the users to switch on/off the auxiliary build and test artifacts.
# These artifacts are NOT part of libpng proper, and are subject to change
# at any time.
option(PNG_TESTS "Build the libpng tests" ON)

# Same as above, but for the third-party tools.
# Although these tools are targetted at development environments only,
# the users are allowed to override the option to build by default.
if(ANDROID OR IOS)
  option(PNG_TOOLS "Build the libpng tools" OFF)
else()
  option(PNG_TOOLS "Build the libpng tools" ON)
endif()

# Maintain backwards compatibility with the deprecated option PNG_EXECUTABLES.
option(PNG_EXECUTABLES "[Deprecated; please use PNG_TOOLS]" ON)
if(NOT PNG_EXECUTABLES)
  message(DEPRECATION "The option PNG_EXECUTABLES has been deprecated in favour of PNG_TOOLS")
  if(PNG_TOOLS)
    message(AUTHOR_WARNING "Setting PNG_TOOLS to ${PNG_EXECUTABLES}, "
                           "to stay compatible with PNG_EXECUTABLES")
    set(PNG_TOOLS "${PNG_EXECUTABLES}")
  endif()
endif()

# Allow the users to switch on/off the use of hardware (SIMD) optimized code.
option(PNG_HARDWARE_OPTIMIZATIONS "Enable hardware optimizations" ON)

# Initialize and show the target architecture variable PNG_TARGET_ARCHITECTURE.
#
# NOTE:
# On macOS, CMake sets CMAKE_SYSTEM_PROCESSOR to either "x86_64" or "arm64",
# based upon the OS architecture, not the target architecture. As such, we need
# to check CMAKE_OSX_ARCHITECTURES to identify which hardware-specific flags to
# enable. Note that this will fail if you attempt to build a universal binary
# in a single CMake invocation.
if(APPLE AND CMAKE_OSX_ARCHITECTURES)
  string(TOLOWER "${CMAKE_OSX_ARCHITECTURES}" PNG_TARGET_ARCHITECTURE)
else()
  string(TOLOWER "${CMAKE_SYSTEM_PROCESSOR}" PNG_TARGET_ARCHITECTURE)
endif()
message(STATUS "Building for target architecture: ${PNG_TARGET_ARCHITECTURE}")

# Allow the users to specify a custom location of zlib.
# With CMake 3.12 and newer, this option is no longer necessary.
option(PNG_BUILD_ZLIB "[Deprecated; please use ZLIB_ROOT]" OFF)
if(PNG_BUILD_ZLIB)
  if("x${ZLIB_ROOT}" STREQUAL "x")
    message(SEND_ERROR "The option PNG_BUILD_ZLIB=${PNG_BUILD_ZLIB} is no longer supported; "
                       "please use ZLIB_ROOT instead")
  else()
    message(SEND_ERROR "The option PNG_BUILD_ZLIB=${PNG_BUILD_ZLIB} is no longer supported; "
                       "using ZLIB_ROOT=\"${ZLIB_ROOT}\"")
  endif()
endif()

# Find the zlib library.
find_package(ZLIB REQUIRED)
set(PNG_LINK_LIBRARIES ZLIB::ZLIB)

# Find the math library (unless we already know it's not available or
# not needed).
if(UNIX AND NOT (APPLE OR BEOS OR HAIKU OR EMSCRIPTEN))
  check_library_exists(m pow "" PNG_HAVE_LIBM_POW)
endif()
if(PNG_HAVE_LIBM_POW)
  list(APPEND PNG_LINK_LIBRARIES m)
endif()

# Silence function deprecation warnings on the Windows compilers that might
# use the MSVC Runtime library headers.
if(WIN32 AND (CMAKE_C_COMPILER_ID MATCHES "MSVC|Intel|Clang"))
  add_definitions(-D_CRT_NONSTDC_NO_DEPRECATE)
  add_definitions(-D_CRT_SECURE_NO_DEPRECATE)
endif()

option(ld-version-script "Enable linker version script" ON)
if(ld-version-script AND NOT (ANDROID OR APPLE))
  # Check if LD supports linker scripts.
  file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/conftest.map" "
VERS_1 { global: sym1; local: *; };
VERS_2 { global: sym2; main; } VERS_1;
")
  set(_SAVED_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
  if(NOT CMAKE_HOST_SOLARIS)
    # Avoid using CMAKE_SHARED_LIBRARY_C_FLAGS in version script checks on
    # Solaris, because of an incompatibility with the Solaris link editor.
    list(APPEND CMAKE_REQUIRED_FLAGS ${CMAKE_SHARED_LIBRARY_C_FLAGS})
  endif()
  list(APPEND CMAKE_REQUIRED_FLAGS
              "-Wl,--version-script='${CMAKE_CURRENT_BINARY_DIR}/conftest.map'")
  check_c_source_compiles("
void sym1(void) {}
void sym2(void) {}
int main(void) { return 0; }
" HAVE_LD_VERSION_SCRIPT)
  if(NOT HAVE_LD_VERSION_SCRIPT)
    set(CMAKE_REQUIRED_FLAGS ${_SAVED_CMAKE_REQUIRED_FLAGS})
    if(NOT CMAKE_HOST_SOLARIS)
      # Again, avoid using CMAKE_SHARED_LIBRARY_C_FLAGS in version script
      # checks on Solaris.
      list(APPEND CMAKE_REQUIRED_FLAGS ${CMAKE_SHARED_LIBRARY_C_FLAGS})
    endif()
    list(APPEND CMAKE_REQUIRED_FLAGS "-Wl,-M -Wl,${CMAKE_CURRENT_BINARY_DIR}/conftest.map")
    check_c_source_compiles("
void sym1(void) {}
void sym2(void) {}
int main(void) { return 0; }
" HAVE_SOLARIS_LD_VERSION_SCRIPT)
  endif()
  set(CMAKE_REQUIRED_FLAGS ${_SAVED_CMAKE_REQUIRED_FLAGS})
  file(REMOVE "${CMAKE_CURRENT_BINARY_DIR}/conftest.map")
endif()

if(PNG_LIBCONF_HEADER STREQUAL "")
  # No custom configuration header file has been specified, so we build it
  # from our DFA files and (optionally) out of the user-supplied DFA file.
  # Find an AWK language processor.
  # Start with specific AWK implementations like gawk and nawk, which are
  # known to work with our scripts, then fall back to the system awk.
  find_program(AWK NAMES gawk nawk awk)
  if(AWK)
    message(STATUS "Found AWK program: ${AWK}")
  else()
    message(STATUS "Could not find an AWK-compatible program")
  endif()
endif()

# Include the internal module PNGCheckLibconf.cmake
include("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGCheckLibconf.cmake")

if(NOT PNG_LIBCONF_HEADER STREQUAL "")
  # Configure libpng with the user-defined pnglibconf.h file.
  png_check_libconf(HEADER "${PNG_LIBCONF_HEADER}")
  configure_file("${PNG_LIBCONF_HEADER}"
                 "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h"
                 @ONLY)
  add_custom_target(png_genfiles)
elseif(NOT AWK)
  # No AWK program available to generate pnglibconf.h.
  # Configure libpng with pnglibconf.h.prebuilt.
  png_check_libconf(HEADER "${PNG_LIBCONF_HEADER_PREBUILT}")
  configure_file("${PNG_LIBCONF_HEADER_PREBUILT}"
                 "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h"
                 @ONLY)
  add_custom_target(png_genfiles)
else()
  png_check_libconf(DFA_XTRA "${DFA_XTRA}")

  # Include the internal module PNGGenConfig.cmake
  include("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGGenConfig.cmake")

  # Work around a limitation of various Windows AWK programs that are
  # unable to process CRLF-terminated AWK scripts.
  # Copy these AWK scripts to a temporary location, converting their
  # line endings from Windows (CRLF) to Unix (LF) at the destination.
  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/checksym.awk"
                 "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/checksym.awk"
                 @ONLY
                 NEWLINE_STYLE LF)
  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/options.awk"
                 "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/options.awk"
                 @ONLY
                 NEWLINE_STYLE LF)
  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/dfn.awk"
                 "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/dfn.awk"
                 @ONLY
                 NEWLINE_STYLE LF)

  # Generate scripts/pnglibconf/pnglibconf.c
  generate_source(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/pnglibconf.c"
                  DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/options.awk"
                          "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/pnglibconf.dfa"
                          "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h")

  # Generate pnglibconf.c
  generate_source(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.c"
                  DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/options.awk"
                          "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/pnglibconf.dfa"
                          "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h")

  if(PNG_PREFIX)
    set(PNGLIBCONF_H_EXTRA_DEPENDS
        "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/prefix.out"
        "${CMAKE_CURRENT_SOURCE_DIR}/scripts/macro.lst")
    set(PNGPREFIX_H_EXTRA_DEPENDS
        "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/intprefix.out")
  endif()

  generate_out(INPUT "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.out")

  # Generate pnglibconf.h
  generate_source(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h"
                  DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.out"
                          ${PNGLIBCONF_H_EXTRA_DEPENDS})

  generate_out(INPUT "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/intprefix.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/intprefix.out"
               DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h")

  generate_out(INPUT "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/prefix.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/prefix.out"
               DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/png.h"
                       "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h"
                       "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.out")

  # Generate pngprefix.h
  generate_source(OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/pngprefix.h"
                  DEPENDS ${PNGPREFIX_H_EXTRA_DEPENDS})

  generate_out(INPUT "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/sym.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/sym.out"
               DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h")

  generate_out(INPUT "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/symbols.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/symbols.out"
               DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/png.h"
                       "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h"
                       "${CMAKE_CURRENT_SOURCE_DIR}/pnglibconf.h.prebuilt")

  generate_out(INPUT "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf/vers.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/vers.out"
               DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/png.h"
                       "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h"
                       "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h")

  generate_chk(INPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/symbols.out"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/symbols.chk"
               DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/checksym.awk"
                       "${CMAKE_CURRENT_SOURCE_DIR}/scripts/symbols.def")

  generate_copy(INPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/sym.out"
                OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym")

  generate_copy(INPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/vers.out"
                OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/libpng.vers")

  add_custom_target(png_genprebuilt
                    COMMAND "${CMAKE_COMMAND}"
                            "-DOUTPUT=pnglibconf.h.prebuilt"
                            -P "${CMAKE_CURRENT_BINARY_DIR}/scripts/cmake/gensrc.cmake"
                    WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}")

  # A single target handles generation of all generated files.
  add_custom_target(png_genfiles
                    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym"
                            "${CMAKE_CURRENT_BINARY_DIR}/libpng.vers"
                            "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.c"
                            "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h"
                            "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.out"
                            "${CMAKE_CURRENT_BINARY_DIR}/pngprefix.h"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/intprefix.out"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/pnglibconf.c"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/prefix.out"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/sym.out"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/symbols.chk"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/symbols.out"
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf/vers.out")
endif()

# List the source code files.
set(libpng_public_hdrs
    png.h
    pngconf.h
    "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h"
)
set(libpng_private_hdrs
    pngpriv.h
    pngdebug.h
    pnginfo.h
    pngstruct.h
)
if(AWK)
  list(APPEND libpng_private_hdrs "${CMAKE_CURRENT_BINARY_DIR}/pngprefix.h")
endif()
set(libpng_sources
    ${libpng_public_hdrs}
    ${libpng_private_hdrs}
    png.c
    pngerror.c
    pngget.c
    pngmem.c
    pngpread.c
    pngread.c
    pngrio.c
    pngrtran.c
    pngrutil.c
    pngset.c
    pngtrans.c
    pngwio.c
    pngwrite.c
    pngwtran.c
    pngwutil.c
    pngsimd.c
)

set(pngtest_sources
    pngtest.c
)
set(pngvalid_sources
    contrib/libtests/pngvalid.c
)
set(pngstest_sources
    contrib/libtests/pngstest.c
)
set(pngunknown_sources
    contrib/libtests/pngunknown.c
)
set(pngimage_sources
    contrib/libtests/pngimage.c
)
set(pngfix_sources
    contrib/tools/pngfix.c
)
set(png_fix_itxt_sources
    contrib/tools/png-fix-itxt.c
)

# Now build our targets.

# Initialize the list of libpng library targets.
set(PNG_LIBRARY_TARGETS "")

# Initialize the libpng library file names.
if(UNIX
   OR (WIN32 AND NOT CMAKE_SHARED_LIBRARY_PREFIX STREQUAL "")
   OR (WIN32 AND NOT CMAKE_STATIC_LIBRARY_PREFIX STREQUAL ""))
  # We are on a Unix or Unix-like toolchain like the GNU toolchain on Windows.
  # Library file names are expected to have an implicit prefix such as "lib".
  # Let CMake prepend and append its usual prefixes and suffixes by default.
  set(PNG_SHARED_OUTPUT_NAME "png${PNGLIB_ABI_VERSION}")
  set(PNG_STATIC_OUTPUT_NAME "png${PNGLIB_ABI_VERSION}")
else()
  # We are, most likely, on a Windows toolchain like MSVC, Clang on Windows,
  # Borland/Embarcadero, etc. We need to specify the "libpng" name explicitly.
  # We also need to use a custom suffix, in order to distinguish between the
  # shared import library name and the static library name.
  set(PNG_SHARED_OUTPUT_NAME "libpng${PNGLIB_ABI_VERSION}")
  set(PNG_STATIC_OUTPUT_NAME "libpng${PNGLIB_ABI_VERSION}_static")
endif()

if(PNG_SHARED)
  add_library(png_shared SHARED ${libpng_sources})
  add_dependencies(png_shared png_genfiles)
  list(APPEND PNG_LIBRARY_TARGETS png_shared)
  set_target_properties(png_shared
                        PROPERTIES OUTPUT_NAME "${PNG_SHARED_OUTPUT_NAME}"
                                   DEBUG_POSTFIX "${PNG_DEBUG_POSTFIX}"
                                   VERSION "${PNGLIB_SHARED_VERSION}"
                                   SOVERSION "${PNGLIB_ABI_VERSION}")
  if(UNIX AND AWK)
    if(HAVE_LD_VERSION_SCRIPT)
      set_target_properties(png_shared
                            PROPERTIES LINK_FLAGS "-Wl,--version-script='${CMAKE_CURRENT_BINARY_DIR}/libpng.vers'")
    elseif(HAVE_SOLARIS_LD_VERSION_SCRIPT)
      set_target_properties(png_shared
                            PROPERTIES LINK_FLAGS "-Wl,-M -Wl,'${CMAKE_CURRENT_BINARY_DIR}/libpng.vers'")
    endif()
  endif()
  if(APPLE)
    # Avoid CMake's implicit compile definition "png_shared_EXPORTS".
    set_target_properties(png_shared
                          PROPERTIES DEFINE_SYMBOL "")
  elseif(WIN32)
    # Use the explicit compile definition "PNG_BUILD_DLL" for Windows DLLs.
    set_target_properties(png_shared
                          PROPERTIES DEFINE_SYMBOL PNG_BUILD_DLL)
  endif()
  target_include_directories(png_shared
                             PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>")
  target_include_directories(png_shared
                             PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}>")
  target_include_directories(png_shared
                             SYSTEM
                             INTERFACE "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/libpng${PNGLIB_ABI_VERSION}>")
  target_link_libraries(png_shared
                        PUBLIC ${PNG_LINK_LIBRARIES})
endif()

if(PNG_STATIC)
  add_library(png_static STATIC ${libpng_sources})
  add_dependencies(png_static png_genfiles)
  list(APPEND PNG_LIBRARY_TARGETS png_static)
  set_target_properties(png_static
                        PROPERTIES OUTPUT_NAME "${PNG_STATIC_OUTPUT_NAME}"
                                   DEBUG_POSTFIX "${PNG_DEBUG_POSTFIX}")
  target_include_directories(png_static
                             PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>")
  target_include_directories(png_static
                             PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}>")
  target_include_directories(png_static
                             SYSTEM
                             INTERFACE "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/libpng${PNGLIB_ABI_VERSION}>")
  target_link_libraries(png_static
                        PUBLIC ${PNG_LINK_LIBRARIES})
endif()

if(PNG_FRAMEWORK AND NOT APPLE)
  message(AUTHOR_WARNING "Setting PNG_FRAMEWORK to OFF, as it only applies to Apple systems")
  set(PNG_FRAMEWORK OFF)
endif()

if(PNG_FRAMEWORK)
  add_library(png_framework SHARED ${libpng_sources})
  add_dependencies(png_framework png_genfiles)
  list(APPEND PNG_LIBRARY_TARGETS png_framework)
  set_target_properties(png_framework
                        PROPERTIES FRAMEWORK TRUE
                                   FRAMEWORK_VERSION "${PNGLIB_VERSION}"
                                   MACOSX_FRAMEWORK_SHORT_VERSION_STRING "${PNGLIB_MAJOR}.${PNGLIB_MINOR}"
                                   MACOSX_FRAMEWORK_BUNDLE_VERSION "${PNGLIB_VERSION}"
                                   MACOSX_FRAMEWORK_IDENTIFIER "org.libpng.libpng"
                                   XCODE_ATTRIBUTE_INSTALL_PATH "@rpath"
                                   PUBLIC_HEADER "${libpng_public_hdrs}"
                                   OUTPUT_NAME "png"
                                   DEBUG_POSTFIX "${PNG_DEBUG_POSTFIX}")
  # Avoid CMake's implicit compile definition "-Dpng_framework_EXPORTS".
  set_target_properties(png_framework
                        PROPERTIES DEFINE_SYMBOL "")
  target_include_directories(png_framework
                             PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>")
  target_include_directories(png_framework
                             PUBLIC "$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}>")
  target_include_directories(png_framework
                             SYSTEM
                             INTERFACE "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/libpng${PNGLIB_ABI_VERSION}>")
  target_link_libraries(png_framework
                        PUBLIC ${PNG_LINK_LIBRARIES})
endif()

if(NOT PNG_LIBRARY_TARGETS)
  message(SEND_ERROR "No library variant selected to build. "
                     "Please enable at least one of the following options: "
                     "PNG_SHARED, PNG_STATIC, PNG_FRAMEWORK")
endif()

if(PNG_TESTS AND PNG_SHARED)
  enable_testing()

  # Include the internal module PNGTest.cmake
  include("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGTest.cmake")

  # Find test PNG files by globbing, but sort lists to ensure
  # consistency between different filesystems.
  file(GLOB PNGSUITE_PNGS "${CMAKE_CURRENT_SOURCE_DIR}/contrib/pngsuite/*.png")
  list(SORT PNGSUITE_PNGS)
  file(GLOB TEST_PNGS "${CMAKE_CURRENT_SOURCE_DIR}/contrib/testpngs/*.png")
  list(SORT TEST_PNGS)
  file(GLOB TEST_PNG3_PNGS "${CMAKE_CURRENT_SOURCE_DIR}/contrib/testpngs/png-3/*.png")
  list(SORT TEST_PNG3_PNGS)

  set(PNGTEST_PNG "${CMAKE_CURRENT_SOURCE_DIR}/pngtest.png")

  add_executable(pngtest ${pngtest_sources})
  target_link_libraries(pngtest
                        PRIVATE png_shared)

  png_add_test(NAME pngtest
               COMMAND pngtest
               FILES "${PNGTEST_PNG}")

  png_add_test(NAME pngtest-png-3
               COMMAND pngtest
               FILES "${TEST_PNG3_PNGS}")

  add_executable(pngvalid ${pngvalid_sources})
  target_link_libraries(pngvalid
                        PRIVATE png_shared)

  png_add_test(NAME pngvalid-gamma-16-to-8
               COMMAND pngvalid
               OPTIONS --gamma-16-to-8)
  png_add_test(NAME pngvalid-gamma-alpha-mode
               COMMAND pngvalid
               OPTIONS --gamma-alpha-mode)
  png_add_test(NAME pngvalid-gamma-background
               COMMAND pngvalid
               OPTIONS --gamma-background)
  png_add_test(NAME pngvalid-gamma-expand16-alpha-mode
               COMMAND pngvalid
               OPTIONS --gamma-alpha-mode --expand16)
  png_add_test(NAME pngvalid-gamma-expand16-background
               COMMAND pngvalid
               OPTIONS --gamma-background --expand16)
  png_add_test(NAME pngvalid-gamma-expand16-transform
               COMMAND pngvalid
               OPTIONS --gamma-transform --expand16)
  png_add_test(NAME pngvalid-gamma-sbit
               COMMAND pngvalid
               OPTIONS --gamma-sbit)
  png_add_test(NAME pngvalid-gamma-threshold
               COMMAND pngvalid
               OPTIONS --gamma-threshold)
  png_add_test(NAME pngvalid-gamma-transform
               COMMAND pngvalid
               OPTIONS --gamma-transform)
  png_add_test(NAME pngvalid-progressive-interlace-standard
               COMMAND pngvalid
               OPTIONS --standard --progressive-read --interlace)
  png_add_test(NAME pngvalid-progressive-size
               COMMAND pngvalid
               OPTIONS --size --progressive-read)
  png_add_test(NAME pngvalid-progressive-standard
               COMMAND pngvalid
               OPTIONS --standard --progressive-read)
  png_add_test(NAME pngvalid-standard
               COMMAND pngvalid
               OPTIONS --standard)
  png_add_test(NAME pngvalid-transform
               COMMAND pngvalid
               OPTIONS --transform)

  add_executable(pngstest ${pngstest_sources})
  target_link_libraries(pngstest
                        PRIVATE png_shared)

  foreach(gamma_type 1.8 linear none sRGB)
    foreach(alpha_type none alpha)
      set(PNGSTEST_FILES)
      foreach(test_png ${TEST_PNGS})
        string(REGEX MATCH "-linear[-.]" TEST_PNG_LINEAR "${test_png}")
        string(REGEX MATCH "-sRGB[-.]" TEST_PNG_SRGB "${test_png}")
        string(REGEX MATCH "-1.8[-.]" TEST_PNG_G18 "${test_png}")
        string(REGEX MATCH "-alpha-" TEST_PNG_ALPHA "${test_png}")

        set(TEST_PNG_VALID TRUE)

        if(TEST_PNG_ALPHA)
          if(NOT alpha_type STREQUAL "alpha")
            set(TEST_PNG_VALID FALSE)
          endif()
        else()
          if(alpha_type STREQUAL "alpha")
            set(TEST_PNG_VALID FALSE)
          endif()
        endif()

        if(TEST_PNG_LINEAR)
          if(NOT gamma_type STREQUAL "linear")
            set(TEST_PNG_VALID FALSE)
          endif()
        elseif(TEST_PNG_SRGB)
          if(NOT gamma_type STREQUAL "sRGB")
            set(TEST_PNG_VALID FALSE)
          endif()
        elseif(TEST_PNG_G18)
          if(NOT gamma_type STREQUAL "1.8")
            set(TEST_PNG_VALID FALSE)
          endif()
        else()
          if(NOT gamma_type STREQUAL "none")
            set(TEST_PNG_VALID FALSE)
          endif()
        endif()

        if(TEST_PNG_VALID)
          list(APPEND PNGSTEST_FILES "${test_png}")
        endif()
      endforeach()
      # Should already be sorted, but sort anyway to be certain.
      list(SORT PNGSTEST_FILES)
      png_add_test(NAME pngstest-${gamma_type}-${alpha_type}
                   COMMAND pngstest
                   OPTIONS --tmpfile "${gamma_type}-${alpha_type}-" --log
                   FILES ${PNGSTEST_FILES})
    endforeach()
  endforeach()

  add_executable(pngunknown ${pngunknown_sources})
  target_link_libraries(pngunknown
                        PRIVATE png_shared)

  png_add_test(NAME pngunknown-discard
               COMMAND pngunknown
               OPTIONS --strict default=discard
               FILES "${PNGTEST_PNG}")
  png_add_test(NAME pngunknown-IDAT
               COMMAND pngunknown
               OPTIONS --strict default=discard IDAT=save
               FILES "${PNGTEST_PNG}")
  png_add_test(NAME pngunknown-if-safe
               COMMAND pngunknown
               OPTIONS --strict default=if-safe
               FILES "${PNGTEST_PNG}")
  png_add_test(NAME pngunknown-sAPI
               COMMAND pngunknown
               OPTIONS --strict
                       bKGD=save cHRM=save gAMA=save all=discard iCCP=save sBIT=save sRGB=save
               FILES "${PNGTEST_PNG}")
  png_add_test(NAME pngunknown-save
               COMMAND pngunknown
               OPTIONS --strict default=save
               FILES "${PNGTEST_PNG}")
  png_add_test(NAME pngunknown-sTER
               COMMAND pngunknown
               OPTIONS --strict sTER=if-safe
               FILES "${PNGTEST_PNG}")
  png_add_test(NAME pngunknown-vpAg
               COMMAND pngunknown
               OPTIONS --strict vpAg=if-safe
               FILES "${PNGTEST_PNG}")

  add_executable(pngimage ${pngimage_sources})
  target_link_libraries(pngimage
                        PRIVATE png_shared)

  png_add_test(NAME pngimage-quick
               COMMAND pngimage
               OPTIONS --list-combos --log
               FILES ${PNGSUITE_PNGS})
  png_add_test(NAME pngimage-full
               COMMAND pngimage
               OPTIONS --exhaustive --list-combos --log
               FILES ${PNGSUITE_PNGS})
endif()

if(PNG_SHARED AND PNG_TOOLS)
  add_executable(pngfix ${pngfix_sources})
  target_link_libraries(pngfix
                        PRIVATE png_shared)
  set(PNG_BIN_TARGETS pngfix)

  add_executable(png-fix-itxt ${png_fix_itxt_sources})
  target_link_libraries(png-fix-itxt
                        PRIVATE ${PNG_LINK_LIBRARIES})
  list(APPEND PNG_BIN_TARGETS png-fix-itxt)
endif()

# Create a symlink that points to a target file (if symlinking is possible),
# or make a copy of the target file (if symlinking is not possible):
# create_symlink(<destfile> [FILE <file> | TARGET <target>])
function(create_symlink DEST_FILE)
  # TODO:
  # Replace this implementation with CMake's built-in create_symlink function,
  # which has been fully functional on all platforms, including Windows, since
  # CMake version 3.13.
  cmake_parse_arguments(_SYM "" "FILE;TARGET" "" ${ARGN})
  if(NOT _SYM_FILE AND NOT _SYM_TARGET)
    message(FATAL_ERROR "create_symlink: Missing arguments: FILE or TARGET")
  endif()
  if(_SYM_FILE AND _SYM_TARGET)
    message(FATAL_ERROR "create_symlink: Mutually-exlusive arguments:"
                        "FILE (${_SYM_FILE}) and TARGET (${_SYM_TARGET})")
  endif()

  if(_SYM_FILE)
    # If we don't need to symlink something that's coming from a build target,
    # we can go ahead and symlink/copy at configure time.
    if(CMAKE_HOST_WIN32 AND NOT CYGWIN)
      execute_process(COMMAND "${CMAKE_COMMAND}"
                              -E copy_if_different
                              "${_SYM_FILE}"
                              "${DEST_FILE}"
                      WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}")
    else()
      execute_process(COMMAND "${CMAKE_COMMAND}"
                              -E create_symlink
                              "${_SYM_FILE}"
                              "${DEST_FILE}"
                      WORKING_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}")
    endif()
  endif()

  if(_SYM_TARGET)
    # We need to use generator expressions, which can be a bit tricky.
    # For simplicity, make the symlink a POST_BUILD step, and use the TARGET
    # signature of add_custom_command.
    if(CMAKE_HOST_WIN32 AND NOT CYGWIN)
      add_custom_command(TARGET ${_SYM_TARGET}
                         POST_BUILD
                         COMMAND "${CMAKE_COMMAND}"
                                 -E copy_if_different
                                 "$<TARGET_LINKER_FILE_DIR:${_SYM_TARGET}>/$<TARGET_LINKER_FILE_NAME:${_SYM_TARGET}>"
                                 "$<TARGET_LINKER_FILE_DIR:${_SYM_TARGET}>/${DEST_FILE}")
    else()
      add_custom_command(TARGET ${_SYM_TARGET}
                         POST_BUILD
                         COMMAND "${CMAKE_COMMAND}"
                                 -E create_symlink
                                 "$<TARGET_LINKER_FILE_NAME:${_SYM_TARGET}>"
                                 "$<TARGET_LINKER_FILE_DIR:${_SYM_TARGET}>/${DEST_FILE}")
    endif()
  endif()
endfunction()

# Create source generation scripts.
configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/genchk.cmake.in"
               "${CMAKE_CURRENT_BINARY_DIR}/scripts/cmake/genchk.cmake"
               @ONLY)
configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/genout.cmake.in"
               "${CMAKE_CURRENT_BINARY_DIR}/scripts/cmake/genout.cmake"
               @ONLY)
configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/gensrc.cmake.in"
               "${CMAKE_CURRENT_BINARY_DIR}/scripts/cmake/gensrc.cmake"
               @ONLY)

# libpng is a library so default to 'lib'
if(NOT DEFINED CMAKE_INSTALL_LIBDIR)
  set(CMAKE_INSTALL_LIBDIR lib)
endif()

# Create pkgconfig files.
# We use the same files like ./configure, so we have to set its vars.
# Only do this on Windows for Cygwin - the files don't make much sense
# outside of a UNIX look-alike.
if(NOT WIN32 OR CYGWIN OR MINGW)
  set(prefix "${CMAKE_INSTALL_PREFIX}")
  set(exec_prefix "${CMAKE_INSTALL_PREFIX}")
  set(libdir "${CMAKE_INSTALL_FULL_LIBDIR}")
  set(includedir "${CMAKE_INSTALL_FULL_INCLUDEDIR}")
  set(LIBS "-lz -lm")
  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/libpng.pc.in"
                 "${CMAKE_CURRENT_BINARY_DIR}/libpng${PNGLIB_ABI_VERSION}.pc"
                 @ONLY)
  create_symlink(libpng.pc FILE libpng${PNGLIB_ABI_VERSION}.pc)
  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/libpng-config.in"
                 "${CMAKE_CURRENT_BINARY_DIR}/libpng${PNGLIB_ABI_VERSION}-config"
                 @ONLY)
  create_symlink(libpng-config FILE libpng${PNGLIB_ABI_VERSION}-config)
endif()

# Install.
if(NOT SKIP_INSTALL_LIBRARIES AND NOT SKIP_INSTALL_ALL)
  install(TARGETS ${PNG_LIBRARY_TARGETS}
          EXPORT libpng
          RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
          LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
          ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
          FRAMEWORK DESTINATION "${CMAKE_INSTALL_LIBDIR}")

  if(PNG_SHARED)
    # Create a symlink for libpng.dll.a => libpng2.dll.a on Cygwin
    if(NOT WIN32 OR CYGWIN OR MINGW)
      create_symlink(libpng${CMAKE_SHARED_LIBRARY_SUFFIX} TARGET png_shared)
      install(FILES "$<TARGET_LINKER_FILE_DIR:png_shared>/libpng${CMAKE_SHARED_LIBRARY_SUFFIX}"
              DESTINATION "${CMAKE_INSTALL_LIBDIR}")
    endif()
  endif()

  if(PNG_STATIC)
    if(NOT WIN32 OR CYGWIN OR MINGW)
      create_symlink(libpng${CMAKE_STATIC_LIBRARY_SUFFIX} TARGET png_static)
      install(FILES "$<TARGET_LINKER_FILE_DIR:png_static>/libpng${CMAKE_STATIC_LIBRARY_SUFFIX}"
              DESTINATION "${CMAKE_INSTALL_LIBDIR}")
    endif()
  endif()
endif()

if(NOT SKIP_INSTALL_HEADERS AND NOT SKIP_INSTALL_ALL)
  install(FILES ${libpng_public_hdrs}
          DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")
  install(FILES ${libpng_public_hdrs}
          DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/libpng${PNGLIB_ABI_VERSION}")
endif()
if(NOT SKIP_INSTALL_EXECUTABLES AND NOT SKIP_INSTALL_ALL)
  if(NOT WIN32 OR CYGWIN OR MINGW)
    install(PROGRAMS "${CMAKE_CURRENT_BINARY_DIR}/libpng-config"
            DESTINATION "${CMAKE_INSTALL_BINDIR}")
    install(PROGRAMS "${CMAKE_CURRENT_BINARY_DIR}/libpng${PNGLIB_ABI_VERSION}-config"
            DESTINATION "${CMAKE_INSTALL_BINDIR}")
  endif()
endif()

if(NOT SKIP_INSTALL_PROGRAMS AND NOT SKIP_INSTALL_ALL)
  install(TARGETS ${PNG_BIN_TARGETS}
          RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
endif()

if(NOT SKIP_INSTALL_FILES AND NOT SKIP_INSTALL_ALL)
  # Install the man pages.
  install(FILES manuals/libpng.3
          DESTINATION "${CMAKE_INSTALL_MANDIR}/man3")
  install(FILES manuals/png.5
          DESTINATION "${CMAKE_INSTALL_MANDIR}/man5")
  # Install the pkg-config files.
  if(NOT CMAKE_HOST_WIN32 OR CYGWIN OR MINGW)
    install(FILES "${CMAKE_CURRENT_BINARY_DIR}/libpng.pc"
            DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
    install(PROGRAMS "${CMAKE_CURRENT_BINARY_DIR}/libpng-config"
            DESTINATION "${CMAKE_INSTALL_BINDIR}")
    install(FILES "${CMAKE_CURRENT_BINARY_DIR}/libpng${PNGLIB_ABI_VERSION}.pc"
            DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
    install(PROGRAMS "${CMAKE_CURRENT_BINARY_DIR}/libpng${PNGLIB_ABI_VERSION}-config"
            DESTINATION "${CMAKE_INSTALL_BINDIR}")
  endif()
endif()

# Create an export file that CMake users can include() to import our targets.
if(NOT SKIP_INSTALL_EXPORT AND NOT SKIP_INSTALL_ALL)
  install(EXPORT libpng
          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libpng"
          FILE libpng${PNGLIB_ABI_VERSION}.cmake)
endif()

# Create a CMake Config File that can be used via find_package(PNG CONFIG)
if(NOT SKIP_INSTALL_CONFIG_FILE AND NOT SKIP_INSTALL_ALL)
  install(TARGETS ${PNG_LIBRARY_TARGETS}
          EXPORT PNGTargets
          RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
          LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
          ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
          FRAMEWORK DESTINATION "${CMAKE_INSTALL_LIBDIR}")

  include(CMakePackageConfigHelpers)
  write_basic_package_version_file(PNGConfigVersion.cmake
                                   VERSION ${PNGLIB_VERSION}
                                   COMPATIBILITY SameMinorVersion)

  install(EXPORT PNGTargets
          FILE PNGTargets.cmake
          NAMESPACE PNG::
          DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/PNG")

  install(FILES "${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGConfig.cmake"
                "${CMAKE_CURRENT_BINARY_DIR}/PNGConfigVersion.cmake"
          DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/PNG")
endif()

# TODO: Create MSVC import lib for MinGW-compiled shared lib.
# pexports libpng.dll > libpng.def
# lib /def:libpng.def /machine:x86