Allow studio to search for models in predetermined search paths.

A future CL will allow users to specify search paths in their settings.

PiperOrigin-RevId: 846240293
Change-Id: I1a1a4027d0fc85004a12fe01a406f50fd929f3e4

src/experimental/platform/helpers.cc

@@ -18,6 +18,7 @@
 #include <cstdint>
 #include <cstdio>
 #include <cstring>
+#include <filesystem>
 #include <fstream>
 #include <ios>
 #include <iterator>
@@ -47,6 +48,47 @@ std::string LoadText(const std::string& filename) {
   return contents;
 }
 
+static std::string CheckPathForFile(const std::filesystem::path& path,
+                                    const std::string& filename) {
+  std::filesystem::path resolved = path / filename;
+  if (std::filesystem::exists(resolved)) {
+    return resolved.string();
+  }
+  resolved += ".xml";
+  if (std::filesystem::exists(resolved)) {
+    return resolved.string();
+  }
+  return "";
+}
+
+std::string ResolveFile(const std::string& filename,
+                        const std::vector<std::string>& search_paths) {
+  if (std::filesystem::exists(filename)) {
+    return filename;
+  }
+
+  std::string resolved;
+  for (const std::string& path : search_paths) {
+    if (!std::filesystem::exists(path) ||
+        !std::filesystem::is_directory(path)) {
+      continue;
+    }
+
+    resolved = CheckPathForFile(std::filesystem::path(path), filename);
+    if (!resolved.empty()) {
+      return resolved;
+    }
+
+    for (const auto& it : std::filesystem::recursive_directory_iterator(path)) {
+      resolved = CheckPathForFile(it.path(), filename);
+      if (!resolved.empty()) {
+        return resolved;
+      }
+    }
+  }
+  return "";
+}
+
 void SaveColorToWebp(int width, int height, const unsigned char* data,
                      const std::string& filename) {
   uint8_t* webp = nullptr;

src/experimental/platform/helpers.h

@@ -34,6 +34,11 @@ using LoadAssetFn = std::function<std::vector<std::byte>(std::string_view)>;
 void SaveText(const std::string& contents, const std::string& filename);
 std::string LoadText(const std::string& filename);
 
+// Attempts to find a file with the given name by recursively searching the
+// given search paths.
+std::string ResolveFile(const std::string& filename,
+                        const std::vector<std::string>& search_paths);
+
 // Exports the given color buffer to a webp file.
 void SaveColorToWebp(int width, int height, const unsigned char* data,
                      const std::string& filename);

src/experimental/studio/app.cc

@@ -201,10 +201,12 @@ void App::LoadModel(std::string data, ContentType type) {
       // Store the file path as the model name. Note that we use this model name
       // to perform reload operations.
       model_name_ = std::move(data);
-      if (model_name_.ends_with(".mjb")) {
-        model_ = mj_loadModel(model_name_.c_str(), 0);
-      } else if (model_name_.ends_with(".xml")) {
-        spec_ = mj_parseXML(model_name_.c_str(), nullptr, err, sizeof(err));
+      const std::string resolved_file =
+        platform::ResolveFile(model_name_, search_paths_);
+    if (resolved_file.ends_with(".mjb")) {
+        model_ = mj_loadModel(resolved_file.c_str(), 0);
+      } else if (resolved_file.ends_with(".xml")) {
+        spec_ = mj_parseXML(resolved_file.c_str(), nullptr, err, sizeof(err));
         if (spec_ && err[0] == 0) {
           model_ = mj_compile(spec_, nullptr);
         }

src/experimental/studio/app.h

@@ -185,6 +185,8 @@ class App {
   platform::SimProfiler profiler_;
   platform::SimHistory history_;
 
+  std::vector<std::string> search_paths_;
+
   mjSpec* spec_ = nullptr;
   mjModel* model_ = nullptr;
   mjData* data_ = nullptr;