Add mjmTexture to C API.

PiperOrigin-RevId: 606543622
Change-Id: I2db743c1c40116f0503329fb1d004d9b041e83e7

src/user/user_api.cc

@@ -137,6 +137,15 @@ mjmFrame* mjm_addFrame(mjmBody* bodyspec, mjmFrame* parentframe) {
 
 
 
+// add texture to model
+mjmTexture* mjm_addTexture(void* model) {
+  mjCModel* modelC = static_cast<mjCModel*>(model);
+  mjCTexture* texture = modelC->AddTexture();
+  return &texture->spec;
+}
+
+
+
 // add material to model
 mjmMaterial* mjm_addMaterial(void* model, void* defspec) {
   mjCModel* modelC = static_cast<mjCModel*>(model);
@@ -312,6 +321,19 @@ void mjm_setString(mjString dest, const char* text) {
 
 
 
+// Set specific entry in destination string vector.
+mjtByte mjm_setInStringVec(mjStringVec dest, int i, const char* text) {
+  std::vector<std::string>* v = reinterpret_cast<std::vector<std::string>*>(dest);
+  if (v->size() <= i) {
+    mju_error("Requested index in mjm_setInStringVec is out of bounds");
+    return 0;
+  }
+  v->at(i) = std::string(text);
+  return 1;
+}
+
+
+
 // split text and copy into string array
 void mjm_setStringVec(mjStringVec dest, const char* text) {
   std::vector<std::string>* v = reinterpret_cast<std::vector<std::string>*>(dest);