Disable spec editor when no spec is available.

PiperOrigin-RevId: 942493527
Change-Id: I90e1a0049b9cc9a82a5ede3a4a74a41425d5bee3

src/experimental/platform/ux/spec_editor.cc

@@ -24,6 +24,11 @@ namespace mujoco::platform {
 
 SpecEditor::SpecEditor(int history_size) : capacity_(history_size) {}
 
+void SpecEditor::Reset() {
+  ref_spec_.reset();
+  active_spec_.reset();
+}
+
 void SpecEditor::Reset(const mjSpec& spec) {
   active_element_key_ = kInvalidElementKey;
   active_element_ = nullptr;
@@ -55,6 +60,10 @@ void SpecEditor::Reset(const mjSpec& spec) {
 }
 
 std::unique_ptr<ModelHolder> SpecEditor::Compile() {
+  if (!active_spec_) {
+    return nullptr;
+  }
+
   auto holder = ModelHolder::FromSpec(mj_copySpec(active_spec_.get()));
   if (holder->ok()) {
     ref_spec_ = Copy(active_spec_.get());
@@ -66,6 +75,10 @@ std::unique_ptr<ModelHolder> SpecEditor::Compile() {
 mjSpec* SpecEditor::GetActiveSpec() const { return active_spec_.get(); }
 
 mjsElement* SpecEditor::AddElement(mjtObj type) {
+  if (!active_spec_) {
+    return nullptr;
+  }
+
   // TODO: check that type is only for spec elements.
   mjsElement* element = AddElementToSpec(active_spec_.get(), type);
   if (element) {
@@ -82,6 +95,10 @@ mjsElement* SpecEditor::AddElement(mjtObj type) {
 }
 
 mjsElement* SpecEditor::AddBodyElement(mjsBody* body, mjtObj type) {
+  if (!active_spec_) {
+    return nullptr;
+  }
+
   // TODO: check that type is only for body elements.
   mjsElement* element = AddElementToSpec(active_spec_.get(), type, body);
   if (element) {
@@ -98,6 +115,10 @@ mjsElement* SpecEditor::AddBodyElement(mjsBody* body, mjtObj type) {
 }
 
 void SpecEditor::DeleteActiveElement() {
+  if (!active_spec_) {
+    return;
+  }
+
   if (active_element_) {
     const mjtObj type = active_element_->elemtype;
     const int index = active_map_.Remove(active_element_key_);
@@ -116,6 +137,10 @@ void SpecEditor::DeleteActiveElement() {
 }
 
 void SpecEditor::SetActiveElement(mjsElement* element) {
+  if (!active_spec_) {
+    return;
+  }
+
   if (element == nullptr) {
     ref_element_ = nullptr;
     active_element_ = nullptr;
@@ -152,6 +177,10 @@ void SpecEditor::SetActiveElement(mjsElement* element) {
 }
 
 void SpecEditor::UpdateReferenceElement() {
+  if (!active_spec_) {
+    return;
+  }
+
   if (active_element_ == nullptr) {
     ref_element_ = nullptr;
   } else {
@@ -175,6 +204,10 @@ mjsElement* SpecEditor::GetActiveElement() const { return active_element_; }
 mjsElement* SpecEditor::GetRefElement() const { return ref_element_; }
 
 void SpecEditor::CommitChanges(mjsElement* element) {
+  if (!active_spec_) {
+    return;
+  }
+
   if (element == nullptr) {
     mju_warning("Element is null.");
     return;
@@ -233,6 +266,10 @@ void SpecEditor::Redo() {
 bool SpecEditor::CanRedo() const { return cursor_ < history_.size() - 1; }
 
 void SpecEditor::AppendHistory(HistoryEntry entry) {
+  if (!active_spec_) {
+    return;
+  }
+
   ++cursor_;
   while (history_.size() > cursor_) {
     history_.pop_back();

src/experimental/platform/ux/spec_editor.h

@@ -38,6 +38,9 @@ class SpecEditor {
  public:
   explicit SpecEditor(int history_size = 256);
 
+  // Resets the editor with an empty spec. No editing will be allowed.
+  void Reset();
+
   // Resets the editor to manage the given spec, clearing all cached data.
   // Assumes the given spec is correctly formed (i.e. compilable).
   void Reset(const mjSpec& spec);

src/experimental/studio/app.cc

@@ -161,7 +161,11 @@ void App::LoadModelFromFile(const std::string& filepath) {
   model_holder_ = platform::ModelHolder::FromFile(resolved_file);
   if (model_holder_->ok()) {
     OnModelLoaded(filepath, kModelFromFile);
-    spec_editor_.Reset(*spec());
+    if (spec()) {
+      spec_editor_.Reset(*spec());
+    } else {
+      spec_editor_.Reset();
+    }
     UpdateFilePaths(resolved_file);
     if (model() && model()->names) {
       // Assumes the first string in the model is the name of the model itself.
@@ -188,7 +192,11 @@ void App::LoadModelFromBuffer(std::span<const std::byte> buffer,
   } else {
     SetLoadError(std::string(model_holder_->error()));
   }
-  spec_editor_.Reset(*spec());
+  if (spec()) {
+    spec_editor_.Reset(*spec());
+  } else {
+    spec_editor_.Reset();
+  }
 }
 
 void App::OnModelLoaded(std::string filename, ModelKind model_kind) {