feat(materialx): Add vertex data block handling in shader generation

src/services/impl/materialx_shader_generator.cpp

@@ -10,11 +10,73 @@
 #include <MaterialXGenShader/Util.h>
 #include <MaterialXRender/Util.h>
 
+#include <optional>
 #include <stdexcept>
+#include <string>
 
 namespace sdl3cpp::services::impl {
 namespace mx = MaterialX;
 
+namespace {
+
+bool HasVertexDataBlock(const std::string& source) {
+    return source.find("VertexData") != std::string::npos
+        && source.find("vd;") != std::string::npos;
+}
+
+std::optional<std::string> ExtractVertexDataBlock(const std::string& source) {
+    const std::string marker = "VertexData";
+    const std::string instance = "vd;";
+    size_t blockPos = source.find(marker);
+    if (blockPos == std::string::npos) {
+        return std::nullopt;
+    }
+    size_t instancePos = source.find(instance, blockPos);
+    if (instancePos == std::string::npos) {
+        return std::nullopt;
+    }
+    size_t lineStart = source.rfind('\n', blockPos);
+    if (lineStart == std::string::npos) {
+        lineStart = 0;
+    } else {
+        ++lineStart;
+    }
+    size_t lineEnd = source.find('\n', instancePos);
+    if (lineEnd == std::string::npos) {
+        lineEnd = source.size();
+    }
+    return source.substr(lineStart, lineEnd - lineStart);
+}
+
+std::string ToVertexOutputBlock(std::string block) {
+    const std::string inToken = " in VertexData";
+    const std::string outToken = " out VertexData";
+    size_t tokenPos = block.find(inToken);
+    if (tokenPos != std::string::npos) {
+        block.replace(tokenPos, inToken.size(), outToken);
+        return block;
+    }
+    tokenPos = block.find("in VertexData");
+    if (tokenPos != std::string::npos) {
+        block.replace(tokenPos, std::string("in VertexData").size(), "out VertexData");
+    }
+    return block;
+}
+
+void InsertAfterVersion(std::string& source, const std::string& block) {
+    size_t lineEnd = source.find('\n');
+    if (lineEnd == std::string::npos) {
+        source.append("\n");
+        source.append(block);
+        source.append("\n");
+        return;
+    }
+    ++lineEnd;
+    source.insert(lineEnd, block + "\n");
+}
+
+}  // namespace
+
 MaterialXShaderGenerator::MaterialXShaderGenerator(std::shared_ptr<ILogger> logger)
     : logger_(std::move(logger)) {}
 
@@ -159,6 +221,27 @@ ShaderPaths MaterialXShaderGenerator::Generate(const MaterialXConfig& config,
     ShaderPaths paths;
     paths.vertexSource = shader->getSourceCode(mx::Stage::VERTEX);
     paths.fragmentSource = shader->getSourceCode(mx::Stage::PIXEL);
+
+    const bool vertexHasBlock = HasVertexDataBlock(paths.vertexSource);
+    const bool fragmentHasBlock = HasVertexDataBlock(paths.fragmentSource);
+    if (!vertexHasBlock && fragmentHasBlock) {
+        auto fragmentBlock = ExtractVertexDataBlock(paths.fragmentSource);
+        if (fragmentBlock) {
+            std::string vertexBlock = ToVertexOutputBlock(*fragmentBlock);
+            InsertAfterVersion(paths.vertexSource, vertexBlock);
+            if (logger_) {
+                logger_->Trace("MaterialXShaderGenerator", "Generate",
+                               "vertexDataBlock=inserted");
+            }
+        } else if (logger_) {
+            logger_->Trace("MaterialXShaderGenerator", "Generate",
+                           "vertexDataBlock=missing");
+        }
+    } else if (logger_) {
+        logger_->Trace("MaterialXShaderGenerator", "Generate",
+                       "vertexDataBlock=" + std::string(vertexHasBlock ? "present" : "absent") +
+                       ", fragmentVertexDataBlock=" + std::string(fragmentHasBlock ? "present" : "absent"));
+    }
     return paths;
 }