Updating to new zlib config

CMakeLists.txt

@@ -137,8 +137,34 @@ if(PNG_BUILD_ZLIB)
   endif()
 endif()
 
-# Find the zlib library.
-find_package(ZLIB REQUIRED)
+# Check for useable config from zlib first
+if(PNG_SHARED)
+  list(APPEND PNG_ZLIB_COMPONENTS "shared")
+endif()
+
+if(PNG_STATIC)
+  list(APPEND PNG_ZLIB_COMPONENTS "static")
+  set(PNG_LINK_LIBRARIES_STATIC ZLIB::ZLIBSTATIC)
+else()
+  set(PNG_LINK_LIBRARIES_STATIC ZLIB::ZLIB)
+endif()
+
+find_package(ZLIB CONFIG COMPONENTS ${PNG_ZLIB_COMPONENTS})
+
+# Find the zlib library the old way if config is not present
+if(NOT ZLIB_DIR)
+  find_package(ZLIB REQUIRED)
+else()
+  set(ZLIB_CONFIG True) # Needed in PNGConfig.cmake
+  get_target_property(ZLIB_INCLUDE_DIRS
+                      ${PNG_LINK_LIBRARIES_STATIC}
+                      INTERFACE_INCLUDE_DIRECTORIES)
+endif()
+
+if(NOT TARGET ZLIB::ZLIBSTATIC)
+  add_library(ZLIB::ZLIBSTATIC ALIAS ZLIB::ZLIB)
+endif(NOT TARGET ZLIB::ZLIBSTATIC)
+
 set(PNG_LINK_LIBRARIES ZLIB::ZLIB)
 
 # Find the math library (unless we already know it's not available or
@@ -148,6 +174,7 @@ if(UNIX AND NOT (APPLE OR BEOS OR HAIKU OR EMSCRIPTEN))
 endif()
 if(PNG_HAVE_LIBM_POW)
   list(APPEND PNG_LINK_LIBRARIES m)
+  list(APPEND PNG_LINK_LIBRARIES_STATIC m)
 endif()
 
 # Silence function deprecation warnings on the Windows compilers that might
@@ -476,7 +503,7 @@ if(PNG_STATIC)
                              SYSTEM
                              INTERFACE "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/libpng${PNGLIB_ABI_VERSION}>")
   target_link_libraries(png_static
-                        PUBLIC ${PNG_LINK_LIBRARIES})
+                        PUBLIC ${PNG_LINK_LIBRARIES_STATIC})
 endif()
 
 if(PNG_FRAMEWORK AND NOT APPLE)
@@ -892,6 +919,9 @@ if(NOT SKIP_INSTALL_CONFIG_FILE AND NOT SKIP_INSTALL_ALL)
           ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
           FRAMEWORK DESTINATION "${CMAKE_INSTALL_LIBDIR}")
 
+  configure_file("${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGConfig.cmake.in"
+                 "${CMAKE_CURRENT_BINARY_DIR}/scripts/cmake/PNGConfig.cmake"
+                 @ONLY)
   include(CMakePackageConfigHelpers)
   write_basic_package_version_file(PNGConfigVersion.cmake
                                    VERSION ${PNGLIB_VERSION}
@@ -902,7 +932,7 @@ if(NOT SKIP_INSTALL_CONFIG_FILE AND NOT SKIP_INSTALL_ALL)
           NAMESPACE PNG::
           DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/PNG")
 
-  install(FILES "${CMAKE_CURRENT_SOURCE_DIR}/scripts/cmake/PNGConfig.cmake"
+  install(FILES "${CMAKE_CURRENT_BINARY_DIR}/scripts/cmake/PNGConfig.cmake"
                 "${CMAKE_CURRENT_BINARY_DIR}/PNGConfigVersion.cmake"
           DESTINATION "${CMAKE_INSTALL_LIBDIR}/cmake/PNG")
 endif()

scripts/cmake/PNGConfig.cmake.in

@@ -0,0 +1,62 @@
+# PNGConfig.cmake
+# CMake config file compatible with the FindPNG module.
+
+# Copyright (c) 2024 Cosmin Truta
+# Written by Benjamin Buch, 2024
+#
+# 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
+#
+# SPDX-License-Identifier: libpng-2.0
+
+include(CMakeFindDependencyMacro)
+
+if(@PNG_SHARED@)
+  list(APPEND _PNG_supported_components "shared")
+endif()
+
+if(@PNG_STATIC@)
+  list(APPEND _PNG_supported_components "static")
+endif()
+
+if(@ZLIB_CONFIG@)
+  if(PNG_FIND_COMPONENTS)
+    foreach(_comp ${PNG_FIND_COMPONENTS})
+        if(NOT _comp IN_LIST _PNG_supported_components)
+          set(PNG_FOUND False)
+          set(PNG_NOT_FOUND_MESSAGE "Unsupported component: ${_comp} - Only ${_PNG_supported_components} are available")
+        endif()
+    endforeach()
+
+    find_dependency(ZLIB CONFIG COMPONENTS ${PNG_FIND_COMPONENTS})
+  else()
+    find_dependency(ZLIB CONFIG)
+  endif()
+else()
+  find_dependency(ZLIB REQUIRED)
+endif()
+
+if(NOT TARGET ZLIB::ZLIBSTATIC)
+  add_library(ZLIB::ZLIBSTATIC ALIAS ZLIB::ZLIB)
+endif(NOT TARGET ZLIB::ZLIBSTATIC)
+
+include("${CMAKE_CURRENT_LIST_DIR}/PNGTargets.cmake")
+
+foreach(_comp ${PNG_FIND_COMPONENTS})
+  if(NOT TARGET png::png_${_comp})
+    set(PNG_FOUND False)
+    set(PNG_NOT_FOUND_MESSAGE "${_comp} was not found - Only ${_PNG_supported_components} are available")
+  endif()
+endforeach
+
+if(NOT TARGET PNG::PNG)
+  if(TARGET PNG::png_shared)
+    add_library(PNG::PNG INTERFACE IMPORTED)
+    target_link_libraries(PNG::PNG INTERFACE PNG::png_shared)
+  elseif(TARGET PNG::png_static)
+    add_library(PNG::PNG INTERFACE IMPORTED)
+    target_link_libraries(PNG::PNG INTERFACE PNG::png_static)
+  endif()
+endif()