Feature: Java bindings for libktx (KhronosGroup#481)

Specify KTX_FEATURE_JNI to enable building of libktx_jni and the
corresponding Java wrapper.

Co-authored-by: Mark Callow <2244683+MarkCallow@users.noreply.github.com>

Author: ShukantPal

CMakeLists.txt

@@ -35,6 +35,7 @@ option( KTX_FEATURE_DOC "Create KTX documentation" OFF )
 option( KTX_FEATURE_LOADTEST_APPS "Create load tests apps that load and display various KTX textures" OFF )
 option( KTX_FEATURE_STATIC_LIBRARY "Create static libraries (shared otherwise)" ${LIB_TYPE_DEFAULT} )
 option( KTX_FEATURE_TESTS "Create unit tests" ON )
+option( KTX_FEATURE_JNI "Create Java bindings for libktx" OFF )
 
 set_target_processor_type(CPU_ARCHITECTURE)
 if(CPU_ARCHITECTURE STREQUAL x86_64 OR CPU_ARCHITECTURE STREQUAL x86)
@@ -883,3 +884,5 @@ endif()
 # endif()
 
 include(CPack)
+
+include(cmake/jni.cmake)

cmake/jni.cmake

@@ -0,0 +1,38 @@
+# Copyright (c) 2021, Shukant Pal and Contributors
+# SPDX-License-Identifier: Apache-2.0
+
+if (KTX_FEATURE_JNI)
+    if (DEFINED ENV{JAVA_HOME})
+        include_directories($ENV{JAVA_HOME}/include)
+
+        if (APPLE)
+            include_directories($ENV{JAVA_HOME}/include/darwin)
+        elseif(WIN32)
+            include_directories($ENV{JAVA_HOME}/include/win32)
+        else()
+            include_directories($ENV{JAVA_HOME}/include/linux)
+        endif()
+
+        add_library(ktx-jni SHARED
+            interface/java_binding/src/main/cpp/KtxTexture.cpp
+            interface/java_binding/src/main/cpp/KtxTexture1.cpp
+            interface/java_binding/src/main/cpp/KtxTexture2.cpp
+            interface/java_binding/src/main/cpp/libktx-jni.cpp
+        )
+
+        target_include_directories(ktx-jni PRIVATE include)
+
+        target_link_libraries(ktx-jni ktx)
+
+        if(APPLE)
+            set_target_properties(ktx-jni PROPERTIES
+                XCODE_ATTRIBUTE_ENABLE_HARDENED_RUNTIME "YES"
+                INSTALL_RPATH "@executable_path;/usr/local/lib"
+            )
+        endif()
+
+        install(TARGETS ktx-jni LIBRARY)
+    else()
+        message(FATAL_ERROR "JAVA_HOME is not set with KTX_FEATURE_JNI enabled! Turn it off to skip this.")
+    endif()
+endif()