build: Use libheif exported config if available (#5012)

Needed to change the Libheif::Libheif target we set up ages ago to the
"heif" name that the package's exported config uses.

Also, need to give the warning about static libraries occur any time we
are using static libheif, even if we didn't set LIBSTATIC to try to
force all static libraries.

---------

Signed-off-by: Larry Gritz <lg@larrygritz.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: lgritz

src/cmake/externalpackages.cmake

@@ -163,6 +163,7 @@ checked_find_package (GIF VERSION_MIN 5.0)
 
 # For HEIF/HEIC/AVIF formats
 checked_find_package (Libheif VERSION_MIN 1.11
+                      PREFER_CONFIG
                       RECOMMEND_MIN 1.16
                       RECOMMEND_MIN_REASON "for orientation support")
 

src/cmake/modules/FindLibheif.cmake

@@ -27,7 +27,7 @@ find_library (LIBHEIF_LIBRARY heif
               HINTS
                   ${LIBHEIF_LIBRARY_PATH}
                   ENV LIBHEIF_LIBRARY_PATH
-              DOC "The directory where libheif libraries reside")
+              DOC "The found libheif library")
 
 if (LIBHEIF_INCLUDE_DIR)
     file(STRINGS "${LIBHEIF_INCLUDE_DIR}/libheif/heif_version.h" TMP REGEX "^#define LIBHEIF_VERSION[ \t].*$")
@@ -44,11 +44,11 @@ if (Libheif_FOUND)
     set(LIBHEIF_INCLUDES "${LIBHEIF_INCLUDE_DIR}")
     set(LIBHEIF_LIBRARIES "${LIBHEIF_LIBRARY}")
 
-    if (NOT TARGET Libheif::Libheif)
-        add_library(Libheif::Libheif UNKNOWN IMPORTED)
-        set_target_properties(Libheif::Libheif PROPERTIES
+    if (NOT TARGET heif)
+        add_library(heif UNKNOWN IMPORTED)
+        set_target_properties(heif PROPERTIES
             INTERFACE_INCLUDE_DIRECTORIES "${LIBHEIF_INCLUDES}")
-        set_property(TARGET Libheif::Libheif APPEND PROPERTY
+        set_property(TARGET heif APPEND PROPERTY
             IMPORTED_LOCATION "${LIBHEIF_LIBRARIES}")
     endif ()
 endif()

src/heif.imageio/CMakeLists.txt

@@ -3,31 +3,27 @@
 # https://github.com/AcademySoftwareFoundation/OpenImageIO
 
 if (Libheif_FOUND)
-    if (LINKSTATIC)
-        set (_static_suffixes .lib .a)    
-        set (_static_libraries_found 0)
-
-        foreach (_libeheif_library IN LISTS LIBHEIF_LIBRARIES)
-            get_filename_component (_ext ${_libeheif_library} LAST_EXT)
-            list (FIND _static_suffixes ${_ext} _index)
-            if (${_index} GREATER -1)
-                MATH (EXPR _static_libraries_found "${static_libraries_found}+1")
-            endif()
-        endforeach()
-
-        if (${_static_libraries_found} GREATER 0)
-            message (STATUS "${ColorYellow}")
-            message (STATUS "You are linking OpenImageIO against a static version of libheif, which is LGPL")
-            message (STATUS "licensed. If you intend to redistribute this build of OpenImageIO, we recommend")
-            message (STATUS "that you review the libheif license terms, or you may wish to switch to using a")
-            message (STATUS "dynamically-linked libheif.")
-            message ("${ColorReset}")
+    # Some extra care is needed if the libheif we found was static
+    set (_static_suffixes .lib .a)
+    set (_static_libraries_found 0)
+    foreach (_libeheif_library IN LISTS LIBHEIF_LIBRARIES)
+        get_filename_component (_ext ${_libeheif_library} LAST_EXT)
+        list (FIND _static_suffixes ${_ext} _index)
+        if (${_index} GREATER -1)
+            MATH (EXPR _static_libraries_found "${_static_libraries_found}+1")
         endif()
+    endforeach()
+    if (${_static_libraries_found} GREATER 0)
+        message (STATUS "${ColorYellow}")
+        message (STATUS "You are linking OpenImageIO against a static version of libheif, which is LGPL")
+        message (STATUS "licensed. If you intend to redistribute this build of OpenImageIO, we recommend")
+        message (STATUS "that you review the libheif license terms, or you may wish to switch to using a")
+        message (STATUS "dynamically-linked libheif.")
+        message ("${ColorReset}")
     endif()
 
     add_oiio_plugin (heifinput.cpp heifoutput.cpp
-                     INCLUDE_DIRS ${LIBHEIF_INCLUDES}
-                     LINK_LIBRARIES ${LIBHEIF_LIBRARIES}
+                     LINK_LIBRARIES heif
                      DEFINITIONS "USE_HEIF=1")
 else ()
     message (WARNING "heif plugin will not be built")