Enable test suite rendering on Mac

.github/workflows/main.yml

@@ -78,6 +78,7 @@ jobs:
           compiler_version: "16.4"
           python: 3.13
           test_shaders: ON
+          test_render: ON
 
         - name: MacOS_Xcode_26_Python313
           os: macos-26
@@ -203,7 +204,13 @@ jobs:
             EXTENDED_BUILD_CONFIG="$EXTENDED_BUILD_CONFIG -DMATERIALX_MDL_SDK_DIR=C:/vcpkg/installed/x64-windows"
           fi
         fi
-        cmake -S . -B build -DMATERIALX_BUILD_PYTHON=ON -DMATERIALX_BUILD_VIEWER=ON -DMATERIALX_BUILD_GRAPH_EDITOR=ON -DMATERIALX_BUILD_TESTS=ON -DMATERIALX_TEST_RENDER=OFF -DMATERIALX_WARNINGS_AS_ERRORS=ON $EXTENDED_BUILD_CONFIG ${{matrix.cmake_config}}
+        TEST_RENDER_CONFIG="-DMATERIALX_TEST_RENDER=OFF"
+        if [ "${{ matrix.test_render }}" == "ON" ]; then
+          if [ "${{ runner.os }}" == "macOS" ]; then
+            TEST_RENDER_CONFIG="$TEST_RENDER_CONFIG -DMATERIALX_TEST_RENDER=ON -DMATERIALX_RENDER_MSL_ONLY=ON"
+          fi
+        fi
+        cmake -S . -B build -DMATERIALX_BUILD_PYTHON=ON -DMATERIALX_BUILD_VIEWER=ON -DMATERIALX_BUILD_GRAPH_EDITOR=ON -DMATERIALX_BUILD_TESTS=ON -DMATERIALX_WARNINGS_AS_ERRORS=ON $TEST_RENDER_CONFIG $EXTENDED_BUILD_CONFIG ${{matrix.cmake_config}}
 
     - name: CMake Build
       run: cmake --build build --target install --config Release --parallel 2
@@ -265,13 +272,23 @@ jobs:
         fi
         cppcheck --project=build/compile_commands.json --error-exitcode=1 --suppress=normalCheckLevelMaxBranches --suppress=*:*/External/* --suppress=*:*/NanoGUI/*
 
-    - name: Initialize Virtual Framebuffer
+    - name: Initialize Virtual Framebuffer (Linux)
       if: matrix.test_render == 'ON' && runner.os == 'Linux'
       run: |
         Xvfb :1 -screen 0 1280x960x24 &
         echo "DISPLAY=:1" >> $GITHUB_ENV
         echo "LIBGL_ALWAYS_SOFTWARE=1" >> $GITHUB_ENV
 
+    - name: Initialize Headless Rendering (macOS)
+      if: matrix.test_render == 'ON' && runner.os == 'macOS'
+      run: |
+        # macOS can render headless with Metal backend without virtual display
+        # Force software rendering for Metal backend (more reliable in CI)
+        echo "MTL_HARDWARE_RENDERING=0" >> $GITHUB_ENV
+        # Enable Metal debug layer for better debugging in CI
+        echo "MTL_DEBUG_LAYER=1" >> $GITHUB_ENV
+        echo "LIBGL_ALWAYS_SOFTWARE=1" >> $GITHUB_ENV
+
     - name: Render Script Tests
       if: matrix.test_render == 'ON'
       run: |
@@ -284,6 +301,11 @@ jobs:
       run: |
         ../installed/bin/MaterialXView --material brass_average_baked.mtlx --mesh ../../resources/Geometry/sphere.obj --screenWidth 128 --screenHeight 128 --cameraZoom 1.4 --shadowMap false --captureFilename Viewer_BrassAverage.png
         ../installed/bin/MaterialXView --material usd_preview_surface_carpaint.mtlx --mesh ../../resources/Geometry/sphere.obj --screenWidth 128 --screenHeight 128 --cameraZoom 1.4 --shadowMap false --captureFilename Viewer_CarpaintTranslated.png
+      working-directory: build/render
+
+    - name: Render Application Tests (GraphEditor - Linux only)
+      if: matrix.test_render == 'ON' && runner.os == 'Linux'
+      run: |
         ../installed/bin/MaterialXGraphEditor --material ../../resources/Materials/Examples/StandardSurface/standard_surface_marble_solid.mtlx --viewWidth 128 --viewHeight 128 --captureFilename GraphEditor_MarbleSolid.png
       working-directory: build/render
 
@@ -315,6 +337,25 @@ jobs:
         name: Renders_${{ matrix.name }}
         path: build/render/*.png
 
+    - name: Archive Resources (macOS)
+      if: matrix.test_render == 'ON' && runner.os == 'macOS'
+      run: |
+        mkdir -p build/artifacts
+        if [ ! -d build/bin/resources ]; then
+          echo "Missing build/bin/resources"
+          echo "Contents of build/bin (if present):"
+          ls -la build/bin || true
+          exit 1
+        fi
+        zip -r build/artifacts/resources.zip build/bin/resources
+
+    - name: Upload Resources Archive (macOS)
+      uses: actions/upload-artifact@v4
+      if: matrix.test_render == 'ON' && runner.os == 'macOS'
+      with:
+        name: Resources_${{ matrix.name }}
+        path: build/artifacts/resources.zip
+
     - name: Upload Coverage Report
       uses: actions/upload-artifact@v4
       if: matrix.coverage_analysis == 'ON'

CMakeLists.txt

@@ -45,6 +45,7 @@ option(MATERIALX_BUILD_GEN_MSL "Build the MSL shader generator back-end." ON)
 option(MATERIALX_BUILD_GEN_SLANG "Build the Slang shader generator back-end." ON)
 option(MATERIALX_BUILD_RENDER "Build the MaterialX Render modules." ON)
 option(MATERIALX_BUILD_RENDER_PLATFORMS "Build platform-specific render modules for each shader generator." ON)
+option(MATERIALX_RENDER_MSL_ONLY "On macOS, use Metal Shading Language only for tests and viewer (skips GLSL render tests)." OFF)
 option(MATERIALX_BUILD_OIIO "Build OpenImageIO support for MaterialXRender." OFF)
 option(MATERIALX_BUILD_OCIO "Build OpenColorIO support for shader generators." OFF)
 option(MATERIALX_BUILD_TESTS "Build unit tests." OFF)
@@ -112,6 +113,17 @@ if (MATERIALX_BUILD_JS)
     set(MATERIALX_BUILD_TESTS OFF)
 endif()
 
+# Validate MSL-only rendering option
+if(MATERIALX_RENDER_MSL_ONLY)
+    if(NOT APPLE)
+        message(FATAL_ERROR "MATERIALX_RENDER_MSL_ONLY can only be enabled on Apple platforms")
+    endif()
+    if(NOT MATERIALX_BUILD_GEN_MSL)
+        message(FATAL_ERROR "MATERIALX_RENDER_MSL_ONLY requires MATERIALX_BUILD_GEN_MSL to be enabled")
+    endif()
+    message(STATUS "MSL-only testing mode enabled - MaterialXTest will not link MaterialXRenderGlsl")
+endif()
+
 # All hardware shading languages currently depend on the GLSL shader generator.
 if(MATERIALX_BUILD_GEN_MSL)
     set(MATERIALX_BUILD_GEN_GLSL ON)
@@ -178,6 +190,7 @@ mark_as_advanced(MATERIALX_BUILD_GEN_MSL)
 mark_as_advanced(MATERIALX_BUILD_OSOS)
 mark_as_advanced(MATERIALX_BUILD_RENDER)
 mark_as_advanced(MATERIALX_BUILD_RENDER_PLATFORMS)
+mark_as_advanced(MATERIALX_RENDER_MSL_ONLY)
 mark_as_advanced(MATERIALX_BUILD_OIIO)
 mark_as_advanced(MATERIALX_BUILD_OCIO)
 mark_as_advanced(MATERIALX_BUILD_BENCHMARK_TESTS)

source/MaterialXGraphEditor/Main.cpp

@@ -167,6 +167,12 @@ int main(int argc, char* const argv[])
     glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
 #endif
 
+    // For headless operation (when captureFilename is specified), make window invisible
+    if (!captureFilename.empty())
+    {
+        glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE);
+    }
+
     // Create window with graphics context
     GLFWwindow* window = glfwCreateWindow(1280, 960, "MaterialX Graph Editor", NULL, NULL);
     if (!window)

source/MaterialXTest/CMakeLists.txt

@@ -69,7 +69,7 @@ endif()
 if(MATERIALX_BUILD_RENDER)
   add_subdirectory(MaterialXRender)
   target_link_libraries(MaterialXTest MaterialXRender)
-  if(MATERIALX_BUILD_GEN_GLSL)
+  if(MATERIALX_BUILD_GEN_GLSL AND NOT MATERIALX_RENDER_MSL_ONLY)
     add_subdirectory(MaterialXRenderGlsl)
     target_link_libraries(MaterialXTest MaterialXRenderGlsl)
   endif()

source/MaterialXView/CMakeLists.txt

@@ -11,7 +11,12 @@ if(APPLE)
       set(USE_OPENGL_BACKEND_ON_APPLE_PLATFORM ON)
     endif()
 
-    if(USE_OPENGL_BACKEND_ON_APPLE_PLATFORM)
+    # Force Metal backend if MSL-only rendering is enabled
+    if(MATERIALX_RENDER_MSL_ONLY)
+        set(USE_OPENGL_BACKEND_ON_APPLE_PLATFORM OFF)
+        set(NANOGUI_PREFERRED_BACKEND Metal)
+        set(MATERIALXVIEW_RENDER_BACKEND_DEFINITIONS "-DMATERIALXVIEW_METAL_BACKEND=1")
+    elseif(USE_OPENGL_BACKEND_ON_APPLE_PLATFORM)
         set(NANOGUI_PREFERRED_BACKEND OpenGL)
 	set(MATERIALXVIEW_RENDER_BACKEND_DEFINITIONS "-DMATERIALXVIEW_OPENGL_BACKEND=1")
     else()