Make usdMtlx non-builtin module(built by default)

CMakeLists.txt

@@ -103,6 +103,7 @@ option(TINYUSDZ_CXX_EXCEPTIONS
        "Enable/Disable C++ exceptions(default: Off for posix, on for MSVC)"
        ${TINYUSDZ_CXX_EXCEPTIONS_DEFAULT})
 
+option(TINYUSDZ_WITH_USDMTLX "Build with MaterialX support" ON)
 option(TINYUSDZ_WITH_JSON "Build with JSON serialization support" OFF)
 option(TINYUSDZ_WITH_USDOBJ "Build with usdObj support(import wavefront .obj)"
        ON)
@@ -406,14 +407,7 @@ set(TINYUSDZ_DEP_SOURCES
     ${PROJECT_SOURCE_DIR}/src/lz4/lz4.c
     ${PROJECT_SOURCE_DIR}/src/external/pystring.cpp
     ${PROJECT_SOURCE_DIR}/src/external/staticstruct.cc
-    ${PROJECT_SOURCE_DIR}/src/external/pugixml.cpp
     #${PROJECT_SOURCE_DIR}/src/external/tinyxml2/tinyxml2.cpp
-    #${PROJECT_SOURCE_DIR}/src/external/string_id/string_id.cpp
-    #${PROJECT_SOURCE_DIR}/src/external/string_id/error.cpp
-    #${PROJECT_SOURCE_DIR}/src/external/string_id/generator.cpp
-    #${PROJECT_SOURCE_DIR}/src/external/string_id/database.cpp
-    #${PROJECT_SOURCE_DIR}/src/external/ryu/ryu/s2d.c
-    #${PROJECT_SOURCE_DIR}/src/external/ryu/ryu/s2f.c
 )
 
 if (TINYUSDZ_WITH_BUILTIN_IMAGE_LOADER)
@@ -423,6 +417,9 @@ if (TINYUSDZ_WITH_BUILTIN_IMAGE_LOADER)
                               PROPERTIES COMPILE_DEFINITIONS "FPNG_NO_SSE=1")
 endif()
 
+if(TINYUSDZ_WITH_JSON)
+  list(APPEND TINYUSDZ_DEP_SOURCES ${PROJECT_SOURCE_DIR}/src/external/pugixml.cpp)
+endif()
 
 if(TINYUSDZ_WITH_JSON)
   list(APPEND TINYUSDZ_DEP_SOURCES ${PROJECT_SOURCE_DIR}/src/json-to-usd.cc)
@@ -722,6 +719,11 @@ target_include_directories(tinyusdz_object
 #    PRIVATE ${PROJECT_SOURCE_DIR}/src/external/jsonhpp/)
 #endif()
 
+if(TINYUSDZ_WITH_USDMTLX)
+  target_compile_definitions(tinyusdz_object
+                             PRIVATE "TINYUSDZ_USE_USDMTLX")
+endif()
+
 if(TINYUSDZ_WITH_USDFBX)
   target_compile_definitions(tinyusdz_object
                              PRIVATE "TINYUSDZ_USE_USDFBX")

src/usdMtlx.cc

@@ -1,3 +1,7 @@
+// SPDX-License-Identifier: Apache 2.0
+// Copyright 2023 - Present, Light Transport Entertainment, Inc.
+
+#if defined(TINYUSDZ_USE_USDMTLX)
 
 #ifdef __clang__
 #pragma clang diagnostic push
@@ -10,14 +14,18 @@
 #ifdef __clang__
 #pragma clang diagnostic pop
 #endif
+#endif // TINYUSDZ_USE_USDMTLX
 
 #include <sstream>
 
+#include "usdMtlx.hh"
+
+#if defined(TINYUSDZ_USE_USDMTLX)
+
 #include "io-util.hh"
 #include "tiny-format.hh"
 #include "ascii-parser.hh" // To parse color3f value
 #include "common-macros.inc"
-#include "usdMtlx.hh"
 #include "value-pprint.hh"
 #include "pprinter.hh"
 #include "tiny-format.hh"
@@ -82,7 +90,7 @@ bool is_supported_type(const std::string &typeName) {
   //if (typeName.compare("color") == 0) return true;
   //if (typeName.compare("geomname") == 0) return true;
   //if (typeName.compare("geomnamearray") == 0) return true;
-  
+
   return false;
 }
 
@@ -465,6 +473,38 @@ bool WriteMaterialXToString(const MtlxModel &mtlx, std::string &xml_str,
   return false;
 }
 
-
 //} // namespace usdMtlx
 } // namespace tinyusdz
+
+#else
+
+namespace tinyusdz {
+
+bool ReadMaterialXFromFile(const AssetResolutionResolver &resolver, const std::string &asset_path, MtlxModel *mtlx, std::string *err) {
+
+  (void)resolver;
+  (void)asset_path;
+  (void)mtlx;
+
+  if (err) {
+    (*err) += "MaterialX support is disabled in this build.\n";
+  }
+  return false;
+}
+
+bool WriteMaterialXToString(const MtlxModel &mtlx, std::string &xml_str,
+                             std::string *err) {
+  (void)mtlx;
+  (void)xml_str;
+
+  if (err) {
+    (*err) += "MaterialX support is disabled in this build.\n";
+  }
+  return false;
+}
+
+} // namespace tinyusdz
+
+#endif // TINYUSDZ_USE_USDMTLX
+
+