Use mj_id2name in viewer code where appropriate.

PiperOrigin-RevId: 948945088
Change-Id: I5635c71fd285b128618592699ca64ce8c0f35e31

simulate/simulate.cc

@@ -596,9 +596,9 @@ void DetectImageSensors(mj::Simulate* sim, const mjModel* m) {
 
       // Check if this is an image sensor: width*height*3 == dim
       if (width > 0 && height > 0 && width * height * 3 == dim) {
-        const char* name = m->names + m->name_sensoradr[i];
+        const char* name = mj_id2name(m, mjOBJ_SENSOR, i);
         sim->image_sensor_indices.push_back(i);
-        sim->image_sensor_names.push_back(name);
+        sim->image_sensor_names.push_back(name ? name : "");
         sim->image_sensor_count++;
       }
     }
@@ -932,8 +932,9 @@ void MakeRenderingSection(mj::Simulate* sim, const mjModel* m) {
   for (int i=0; i<mjMIN(m->ncam, mjMAXUIMULTI-2); i++) {
     // prepare name
     char camname[mjMAXUINAME] = "\n";
-    if (m->names[m->name_camadr[i]]) {
-      mju::strcat_arr(camname, m->names+m->name_camadr[i]);
+    const char* name = mj_id2name(m, mjOBJ_CAMERA, i);
+    if (name) {
+      mju::strcat_arr(camname, name);
     } else {
       mju::sprintf_arr(camname, "\nCamera %d", i);
     }
@@ -2529,7 +2530,8 @@ void Simulate::LoadOnRenderThread() {
   jnt_names_.clear();
   jnt_names_.reserve(this->m_->njnt);
   for (int i = 0; i < this->m_->njnt; ++i) {
-    jnt_names_.emplace_back(this->m_->names + this->m_->name_jntadr[i]);
+    const char* name = mj_id2name(this->m_, mjOBJ_JOINT, i);
+    jnt_names_.emplace_back(name ? name : "");
   }
 
   actuator_group_.resize(this->m_->nu);
@@ -2550,13 +2552,15 @@ void Simulate::LoadOnRenderThread() {
   actuator_names_.clear();
   actuator_names_.reserve(this->m_->nu);
   for (int i = 0; i < this->m_->nu; ++i) {
-    actuator_names_.emplace_back(this->m_->names + this->m_->name_actuatoradr[i]);
+    const char* name = mj_id2name(this->m_, mjOBJ_ACTUATOR, i);
+    actuator_names_.emplace_back(name ? name : "");
   }
 
   equality_names_.clear();
   equality_names_.reserve(this->m_->neq);
   for (int i = 0; i < this->m_->neq; ++i) {
-    equality_names_.emplace_back(this->m_->names + this->m_->name_eqadr[i]);
+    const char* name = mj_id2name(this->m_, mjOBJ_EQUALITY, i);
+    equality_names_.emplace_back(name ? name : "");
   }
 
   qpos_.resize(this->m_->nq);

src/experimental/platform/ux/gui.cc

@@ -642,8 +642,8 @@ std::string GetCameraName(const mjModel* model, const mjvCamera& camera,
     return kCameraWasdName;
   } else if (index == kTrackingCameraIdx) {
     return "Tracking (" + std::to_string(camera.trackbodyid) + ")";
-  } else if (model->names[model->name_camadr[index]]) {
-    return std::string(model->names + model->name_camadr[index]);
+  } else if (const char* cam_name = mj_id2name(model, mjOBJ_CAMERA, index)) {
+    return cam_name;
   } else {
     return kCameraUnnamedName;
   }
@@ -1262,8 +1262,8 @@ void JointsGui(const mjModel* model, const mjData* data,
       continue;
     }
 
-    const char* jnt_name = model->names + model->name_jntadr[i];
-    if (*jnt_name) {
+    const char* jnt_name = mj_id2name(model, mjOBJ_JOINT, i);
+    if (jnt_name) {
       std::snprintf(name, sizeof(name), "%s", jnt_name);
     } else {
       std::snprintf(name, sizeof(name), "joint %d", i);
@@ -1315,8 +1315,8 @@ void ControlsGui(const mjModel* model, const mjData* data,
       continue;
     }
 
-    const char* ctrl_name = model->names + model->name_actuatoradr[i];
-    if (*ctrl_name) {
+    const char* ctrl_name = mj_id2name(model, mjOBJ_ACTUATOR, i);
+    if (ctrl_name) {
       std::snprintf(name, sizeof(name), "%s", ctrl_name);
     } else {
       std::snprintf(name, sizeof(name), "control %d", i);

src/experimental/platform/ux/picture_gui.cc

@@ -31,8 +31,8 @@ static bool PipGuiImpl(const mjModel* model, mjData* data, float aspect_ratio,
   bool result = true;
 
   auto get_camera_name = [model](int i) -> const char* {
-    if (model->names[model->name_camadr[i]]) {
-      return model->names + model->name_camadr[i];
+    if (const char* name = mj_id2name(model, mjOBJ_CAMERA, i)) {
+      return name;
     } else {
       return "Unnamed";
     }

src/experimental/studio/app.cc

@@ -1609,9 +1609,8 @@ void App::ModelOptionsGui() {
       ImGui::Spacing();
       {
         char key_fmt[128];
-        const char* key_name =
-            model()->names + model()->name_keyadr[ui_.key_idx];
-        if (key_name[0] != '\0') {
+        const char* key_name = mj_id2name(model(), mjOBJ_KEY, ui_.key_idx);
+        if (key_name) {
           std::snprintf(key_fmt, sizeof(key_fmt), "%s", key_name);
         } else {
           std::snprintf(key_fmt, sizeof(key_fmt), "Key %d", ui_.key_idx);