CMake/Modules/FindPNG.cmake

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Simplify CMake per-source license notices Per-source copyright/license notice headers that spell out copyright holder names and years are hard to maintain and often out-of-date or plain wrong. Precise contributor information is already maintained automatically by the version control tool. Ultimately it is the receiver of a file who is responsible for determining its licensing status, and per-source notices are merely a convenience. Therefore it is simpler and more accurate for each source to have a generic notice of the license name and references to more detailed information on copyright holders and full license terms. Our `Copyright.txt` file now contains a list of Contributors whose names appeared source-level copyright notices. It also references version control history for more precise information. Therefore we no longer need to spell out the list of Contributors in each source file notice. Replace CMake per-source copyright/license notice headers with a short description of the license and links to `Copyright.txt` and online information available from "https://cmake.org/licensing". The online URL also handles cases of modules being copied out of our source into other projects, so we can drop our notices about replacing links with full license text. Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority of the replacements mechanically. Manually fix up shebang lines and trailing newlines in a few files. Manually update the notices in a few files that the script does not handle.
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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.
#.rst:
# FindPNG
# -------
#
# Find libpng, the official reference library for the PNG image format.
#
# Imported targets
# ^^^^^^^^^^^^^^^^
#
# This module defines the following :prop_tgt:`IMPORTED` target:
#
# ``PNG::PNG``
# The libpng library, if found.
#
# Result variables
# ^^^^^^^^^^^^^^^^
#
# This module will set the following variables in your project:
#
# ``PNG_INCLUDE_DIRS``
# where to find png.h, etc.
# ``PNG_LIBRARIES``
# the libraries to link against to use PNG.
# ``PNG_DEFINITIONS``
# You should add_definitons(${PNG_DEFINITIONS}) before compiling code
# that includes png library files.
# ``PNG_FOUND``
# If false, do not try to use PNG.
# ``PNG_VERSION_STRING``
# the version of the PNG library found (since CMake 2.8.8)
#
# Obsolete variables
# ^^^^^^^^^^^^^^^^^^
#
# The following variables may also be set, for backwards compatibility:
#
# ``PNG_LIBRARY``
# where to find the PNG library.
# ``PNG_INCLUDE_DIR``
# where to find the PNG headers (same as PNG_INCLUDE_DIRS)
#
# Since PNG depends on the ZLib compression library, none of the above
# will be defined unless ZLib can be found.
if(PNG_FIND_QUIETLY)
set(_FIND_ZLIB_ARG QUIET)
endif()
find_package(ZLIB ${_FIND_ZLIB_ARG})
if(ZLIB_FOUND)
find_path(PNG_PNG_INCLUDE_DIR png.h
/usr/local/include/libpng # OpenBSD
)
list(APPEND PNG_NAMES png libpng)
unset(PNG_NAMES_DEBUG)
set(_PNG_VERSION_SUFFIXES 17 16 15 14 12)
if (PNG_FIND_VERSION MATCHES "^([0-9]+)\\.([0-9]+)(\\..*)?$")
set(_PNG_VERSION_SUFFIX_MIN "${CMAKE_MATCH_1}${CMAKE_MATCH_2}")
if (PNG_FIND_VERSION_EXACT)
set(_PNG_VERSION_SUFFIXES ${_PNG_VERSION_SUFFIX_MIN})
else ()
string(REGEX REPLACE
"${_PNG_VERSION_SUFFIX_MIN}.*" "${_PNG_VERSION_SUFFIX_MIN}"
_PNG_VERSION_SUFFIXES "${_PNG_VERSION_SUFFIXES}")
endif ()
unset(_PNG_VERSION_SUFFIX_MIN)
endif ()
foreach(v IN LISTS _PNG_VERSION_SUFFIXES)
list(APPEND PNG_NAMES png${v} libpng${v})
list(APPEND PNG_NAMES_DEBUG png${v}d libpng${v}d)
endforeach()
unset(_PNG_VERSION_SUFFIXES)
# For compatibility with versions prior to this multi-config search, honor
# any PNG_LIBRARY that is already specified and skip the search.
if(NOT PNG_LIBRARY)
find_library(PNG_LIBRARY_RELEASE NAMES ${PNG_NAMES})
find_library(PNG_LIBRARY_DEBUG NAMES ${PNG_NAMES_DEBUG})
include(${CMAKE_CURRENT_LIST_DIR}/SelectLibraryConfigurations.cmake)
select_library_configurations(PNG)
mark_as_advanced(PNG_LIBRARY_RELEASE PNG_LIBRARY_DEBUG)
endif()
unset(PNG_NAMES)
unset(PNG_NAMES_DEBUG)
# Set by select_library_configurations(), but we want the one from
# find_package_handle_standard_args() below.
unset(PNG_FOUND)
if (PNG_LIBRARY AND PNG_PNG_INCLUDE_DIR)
# png.h includes zlib.h. Sigh.
set(PNG_INCLUDE_DIRS ${PNG_PNG_INCLUDE_DIR} ${ZLIB_INCLUDE_DIR} )
set(PNG_INCLUDE_DIR ${PNG_INCLUDE_DIRS} ) # for backward compatibility
set(PNG_LIBRARIES ${PNG_LIBRARY} ${ZLIB_LIBRARY})
if (CYGWIN)
if(BUILD_SHARED_LIBS)
# No need to define PNG_USE_DLL here, because it's default for Cygwin.
else()
set (PNG_DEFINITIONS -DPNG_STATIC)
endif()
endif ()
if(NOT TARGET PNG::PNG)
add_library(PNG::PNG UNKNOWN IMPORTED)
set_target_properties(PNG::PNG PROPERTIES
INTERFACE_COMPILE_DEFINITIONS "${PNG_DEFINITIONS}"
INTERFACE_INCLUDE_DIRECTORIES "${PNG_INCLUDE_DIRS}"
INTERFACE_LINK_LIBRARIES ZLIB::ZLIB)
if(EXISTS "${PNG_LIBRARY}")
set_target_properties(PNG::PNG PROPERTIES
IMPORTED_LINK_INTERFACE_LANGUAGES "C"
IMPORTED_LOCATION "${PNG_LIBRARY}")
endif()
if(EXISTS "${PNG_LIBRARY_RELEASE}")
set_property(TARGET PNG::PNG APPEND PROPERTY
IMPORTED_CONFIGURATIONS RELEASE)
set_target_properties(PNG::PNG PROPERTIES
IMPORTED_LINK_INTERFACE_LANGUAGES_RELEASE "C"
IMPORTED_LOCATION_RELEASE "${PNG_LIBRARY_RELEASE}")
endif()
if(EXISTS "${PNG_LIBRARY_DEBUG}")
set_property(TARGET PNG::PNG APPEND PROPERTY
IMPORTED_CONFIGURATIONS DEBUG)
set_target_properties(PNG::PNG PROPERTIES
IMPORTED_LINK_INTERFACE_LANGUAGES_DEBUG "C"
IMPORTED_LOCATION_DEBUG "${PNG_LIBRARY_DEBUG}")
endif()
endif()
endif ()
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if (PNG_PNG_INCLUDE_DIR AND EXISTS "${PNG_PNG_INCLUDE_DIR}/png.h")
file(STRINGS "${PNG_PNG_INCLUDE_DIR}/png.h" png_version_str REGEX "^#define[ \t]+PNG_LIBPNG_VER_STRING[ \t]+\".+\"")
string(REGEX REPLACE "^#define[ \t]+PNG_LIBPNG_VER_STRING[ \t]+\"([^\"]+)\".*" "\\1" PNG_VERSION_STRING "${png_version_str}")
unset(png_version_str)
endif ()
endif()
# handle the QUIETLY and REQUIRED arguments and set PNG_FOUND to TRUE if
# all listed variables are TRUE
Modules: Include builtin FindPackageHandleStandardArgs directly The FindPackageHandleStandardArgs module was originally created outside of CMake. It was added for CMake 2.6.0 by commit e118a627 (add a macro FIND_PACKAGE_HANDLE_STANDARD_ARGS..., 2007-07-18). However, it also proliferated into a number of other projects that at the time required only CMake 2.4 and thus could not depend on CMake to provide the module. CMake's own find modules started using the module in commit b5f656e0 (use the new FIND_PACKAGE_HANDLE_STANDARD_ARGS in some of the FindXXX modules..., 2007-07-18). Then commit d358cf5c (add 2nd, more powerful mode to find_package_handle_standard_args, 2010-07-29) added a new feature to the interface of the module that was fully optional and backward compatible with all existing users of the module. Later commit 5f183caa (FindZLIB: use the FPHSA version mode, 2010-08-04) and others shortly thereafter started using the new interface in CMake's own find modules. This change was also backward compatible because it was only an implementation detail within each module. Unforutnately these changes introduced a problem for projects that still have an old copy of FindPackageHandleStandardArgs in CMAKE_MODULE_PATH. When any such project uses one of CMake's builtin find modules the line include(FindPackageHandleStandardArgs) loads the copy from the project which does not have the new interface! Then the including find module tries to use the new interface with the old module and fails. Whether this breakage can be considered a backward incompatible change in CMake is debatable. The situation is analagous to copying a standard library header from one version of a compiler into a project and then observing problems when the next version of the compiler reports errors in its other headers that depend on its new version of the original header. Nevertheless it is a change to CMake that causes problems for projects that worked with previous versions. This problem was discovered during the 2.8.3 release candidate cycle. It is an instance of a more general problem with projects that provide their own versions of CMake modules when other CMake modules depend on them. At the time we resolved this instance of the problem with commit b0118402 (Use absolute path to FindPackageHandleStandardArgs.cmake everywhere, 2010-09-28) for the 2.8.3 release. In order to address the more general problem we introduced policy CMP0017 in commit db44848f (Prefer files from CMAKE_ROOT when including from CMAKE_ROOT, 2010-11-17). That change was followed by commit ce28737c (Remove usage of CMAKE_CURRENT_LIST_DIR now that we have CMP0017, 2010-12-20) which reverted the original workaround in favor of using the policy. However, existing project releases do not set the policy behavior to NEW and therefore still exhibit the problem. We introduced in commit a364daf1 (Allow users to specify defaults for unset policies, 2011-01-03) an option for users to build existing projects by adding -DCMAKE_POLICY_DEFAULT_CMP0017=NEW to the command line. Unfortunately this solution still does not allow such projects to build out of the box, and there is no good way to suggest the use of the new option. The only remaining solution to keep existing projects that exhibit this problem building is to restore the change originally made in commit b0118402 (Use absolute path to FindPackageHandleStandardArgs.cmake everywhere, 2010-09-28). This also avoids policy CMP0017 warnings for this particular instance of the problem the policy addresses.
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include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
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find_package_handle_standard_args(PNG
REQUIRED_VARS PNG_LIBRARY PNG_PNG_INCLUDE_DIR
VERSION_VAR PNG_VERSION_STRING)
mark_as_advanced(PNG_PNG_INCLUDE_DIR PNG_LIBRARY )