Change KTX_FEATURE_STATIC_LIBRARY to BUILD_SHARED_LIBS (#953)

This changes KTX_FEATURE_STATIC_LIBRARY to the built-in cmake variable
BUILD_SHARED_LIBS.

Static builds are enforced for fmt and astc-encoder. Both libraries use
BUILD_SHARED_LIBS themself, so this fixes issues if KTX-Software
is used as dependecy in other projects (which set BUILD_SHARED_LIBS).

Fixes #935

BUILDING.md

@@ -43,7 +43,7 @@ This creates the `libktx` library and the command line tools. To create the comp
 cmake . -B build -D KTX_FEATURE_LOADTEST_APPS=ON -D KTX_FEATURE_DOC=ON
 ```
 
-If you need the library to be static, add `-D KTX_FEATURE_STATIC_LIBRARY=ON` to the CMake configure command (always enabled on iOS and Emscripten).
+If you need the library to be static, add `-D BUILD_SHARED_LIBS=OFF` to the CMake configure command (always disabled on iOS and Emscripten).
 
 > **Note:**
 >
@@ -522,7 +522,7 @@ cd KTX-Software/
 git submodule update --init --recursive tests/cts
 # Configure 
 mkdir build
-cmake -B build . -DKTX_FEATURE_DOC=ON -DKTX_FEATURE_STATIC_LIBRARY=ON -DKTX_FEATURE_TOOLS_CTS=ON -DKTX_FEATURE_TESTS=ON -DKTX_FEATURE_TOOLS_CTS=ON
+cmake -B build . -DKTX_FEATURE_DOC=ON -DBUILD_SHARED_LIBS=OFF -DKTX_FEATURE_TOOLS_CTS=ON -DKTX_FEATURE_TESTS=ON -DKTX_FEATURE_TOOLS_CTS=ON
 # Build everything (depending on workflow its better to build the specific target like 'ktxtools'):
 cmake --build build --target all 
 # Run every test case:

CMakeLists.txt

@@ -262,12 +262,15 @@ endif()
 
 # EMSCRIPTEN is not set until project so all these must be after.
 if(APPLE_LOCKED_OS OR EMSCRIPTEN)
-    set( LIB_TYPE_DEFAULT ON )
-else()
     set( LIB_TYPE_DEFAULT OFF )
+else()
+    set( LIB_TYPE_DEFAULT ON )
 endif()
 
-option( KTX_FEATURE_STATIC_LIBRARY "Create static libraries (shared otherwise)." ${LIB_TYPE_DEFAULT} )
+option(BUILD_SHARED_LIBS "Create shared libraries (static otherwise)." ${LIB_TYPE_DEFAULT} )
+
+# Used to reset BUILD_SHARED_LIBS after forcing static builds
+set(BUILD_SHARED_LIBS_RESET ${BUILD_SHARED_LIBS})
 
 CMAKE_DEPENDENT_OPTION( KTX_FEATURE_TOOLS
                         "Create KTX tools"
@@ -284,11 +287,11 @@ if(EMSCRIPTEN)
     set( KTX_FEATURE_VK_UPLOAD OFF )
 endif()
 
-if(KTX_FEATURE_STATIC_LIBRARY)
+if(NOT BUILD_SHARED_LIBS)
     set(LIB_TYPE STATIC)
 else()
     if(CMAKE_SYSTEM_NAME STREQUAL "iOS" OR EMSCRIPTEN)
-        message(SEND_ERROR "Library type cannot be shared for the current platform. Set KTX_FEATURE_STATIC_LIBRARY to ON!")
+        message(SEND_ERROR "Library type cannot be shared for the current platform. Set BUILD_SHARED_LIBS to OFF!")
     endif()
     set(LIB_TYPE SHARED)
 endif()
@@ -1116,7 +1119,7 @@ set (STATIC_APP_LIB_SYMBOL_VISIBILITY hidden)
 set_target_properties(objUtil PROPERTIES
     CXX_VISIBILITY_PRESET ${STATIC_APP_LIB_SYMBOL_VISIBILITY}
 )
-if(KTX_FEATURE_STATIC_LIBRARY AND
+if(NOT BUILD_SHARED_LIBS AND
    (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang"))
     set_source_files_properties(
         lib/astc_encode.cpp
@@ -1211,7 +1214,10 @@ if(NOT ${universal_build})
 endif()
 
 set(ASTCENC_CLI OFF) # Only build as library not the CLI astcencoder
+# Force static build for astc-encoder
+set(BUILD_SHARED_LIBS OFF)
 add_subdirectory(external/astc-encoder)
+set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_RESET})
 set_property(TARGET ${ASTCENC_LIB_TARGET} PROPERTY POSITION_INDEPENDENT_CODE ON)
 target_compile_definitions(
     ${ASTCENC_LIB_TARGET}
@@ -1223,7 +1229,7 @@ PRIVATE
     $<$<AND:${is_clangcl},$<VERSION_GREATER_EQUAL:$<CXX_COMPILER_VERSION>,17.0.3>>:_DISABLE_CONSTEXPR_MUTEX_CONSTRUCTOR>
 )
 
-if(KTX_FEATURE_STATIC_LIBRARY AND APPLE)
+if(NOT BUILD_SHARED_LIBS AND APPLE)
     # Make a single static library to simplify linking.
     add_dependencies(ktx ${ASTCENC_LIB_TARGET})
     add_custom_command( TARGET ktx
@@ -1244,9 +1250,12 @@ endif()
 # this CMakeLists is included in another project which is unlikely
 # except for building the ktx library.
 if((KTX_FEATURE_TOOLS OR KTX_FEATURE_TESTS) AND NOT TARGET fmt::fmt)
+    # Always build fmt static
+    set(BUILD_SHARED_LIBS OFF)
     set(FMT_INSTALL OFF)
     set(FMT_SYSTEM_HEADERS ON)
     add_subdirectory(external/fmt)
+    set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_RESET})
 endif()
 if(KTX_FEATURE_TOOLS AND NOT TARGET cxxopts::cxxopts)
     add_subdirectory(external/cxxopts)
@@ -1266,7 +1275,7 @@ if(KTX_FEATURE_DOC)
 endif()
 
 set(KTX_INSTALL_TARGETS ktx)
-if(KTX_FEATURE_STATIC_LIBRARY AND NOT APPLE)
+if(NOT BUILD_SHARED_LIBS AND NOT APPLE)
     list(APPEND KTX_INSTALL_TARGETS ${ASTCENC_LIB_TARGET})
 endif()
 

tests/loadtests/glloadtests.cmake

@@ -229,7 +229,7 @@ function( create_gl_target target version sources common_resources test_images
                 INSTALL_RPATH "@executable_path/../Frameworks"
             )
 
-            if(NOT KTX_FEATURE_STATIC_LIBRARY)
+            if(BUILD_SHARED_LIBS)
               add_custom_command( TARGET ${target} POST_BUILD
                   COMMAND ${CMAKE_COMMAND} -E copy $<TARGET_FILE:ktx> "$<TARGET_BUNDLE_CONTENT_DIR:${target}>/Frameworks/$<TARGET_FILE_NAME:ktx>"
                   COMMAND ${CMAKE_COMMAND} -E create_symlink $<TARGET_FILE_NAME:ktx> "$<TARGET_BUNDLE_CONTENT_DIR:${target}>/Frameworks/$<TARGET_SONAME_FILE_NAME:ktx>"

tests/loadtests/vkloadtests.cmake

@@ -323,7 +323,7 @@ if(APPLE)
             # Set RPATH to find frameworks and dylibs
             INSTALL_RPATH "@executable_path/../Frameworks"
         )
-        if(NOT KTX_FEATURE_STATIC_LIBRARY)
+        if(BUILD_SHARED_LIBS)
             # XCODE_EMBED_FRAMEWORKS does not appear to support generator
             # expressions hence this instead of a genex in the above.
             set_property( TARGET vkloadtests

tests/transcodetests/CMakeLists.txt

@@ -60,7 +60,7 @@ if(WIN32)
 
     # The Windows ktx.dll does not export needed symbols. This is a workaround to get it linking.
     add_library(obj_tmp_basisu OBJECT
-        $<$<NOT:$<BOOL:${KTX_FEATURE_STATIC_LIBRARY}>>:${PROJECT_SOURCE_DIR}/external/basisu/transcoder/basisu_transcoder.cpp>
+        $<$<BOOL:${BUILD_SHARED_LIBS}>:${PROJECT_SOURCE_DIR}/external/basisu/transcoder/basisu_transcoder.cpp>
         "${PROJECT_SOURCE_DIR}/external/basisu/zstd/zstd.c"
         )
     target_compile_definitions(