Add mjz support to studio.

PiperOrigin-RevId: 861627355
Change-Id: Iafd291965ca78d03fdc1efe0e40dabcd4f2dacc4

src/experimental/studio/app.cc

@@ -41,6 +41,7 @@
 #include "experimental/platform/renderer.h"
 #include "experimental/platform/step_control.h"
 #include "experimental/platform/window.h"
+#include "user/user_resource.h"
 
 namespace mujoco::studio {
 
@@ -202,6 +203,22 @@ void App::LoadModelFromFile(const std::string& filepath) {
   mj_deleteVFS(&vfs);
 }
 
+struct BufferProvider : public mjpResourceProvider {
+  BufferProvider(std::span<const std::byte> buffer) : buffer(buffer) {
+    mjp_defaultResourceProvider(this);
+    open = [](mjResource* resource) {
+      return 1;
+    };
+    read = [](mjResource* resource, const void** buffer) {
+      BufferProvider* self = (BufferProvider*)resource->provider;
+      *buffer = self->buffer.data();
+      return static_cast<int>(self->buffer.size());
+    };
+    close = [](mjResource* resource) {};
+  }
+  std::span<const std::byte> buffer;
+};
+
 void App::LoadModelFromBuffer(std::span<const std::byte> buffer,
                               std::string_view content_type,
                               std::string_view filename) {
@@ -217,6 +234,14 @@ void App::LoadModelFromBuffer(std::span<const std::byte> buffer,
     spec = mj_parseXMLString(ptr, nullptr, err, sizeof(err));
   } else if (content_type == "application/mjb") {
     model = mj_loadModelBuffer(buffer.data(), buffer.size());
+  } else if (content_type == "application/zip") {
+    BufferProvider provider(buffer);
+    mjResource resource;
+    memset(&resource, 0, sizeof(mjResource));
+    resource.vfs = &vfs;
+    resource.provider = &provider;
+    resource.name = (char*)filename.data();
+    spec = mju_decodeResource(&resource, content_type.data(), &vfs);
   } else {
     SetLoadError(
         "Unknown content type; expected text/xml or application/mjb");

src/experimental/studio/app.h

@@ -45,11 +45,13 @@ class App {
   void InitEmptyModel();
 
   // Loads an mjModel from the given file. This extension should be one of:
-  // .xml or .mjb.
+  // .xml, .mjb, or .mjz.
   void LoadModelFromFile(const std::string& filepath);
 
   // Loads an mjModel from the given memory buffer. The content_type should be
-  // one of: "text/xml" or "application/mjb".
+  // one of: "text/xml", "application/mjb", or "application/mjz". For zip files,
+  // a name is required in order to uniquely identify the model within the
+  // archive.
   void LoadModelFromBuffer(std::span<const std::byte> buffer,
                            std::string_view content_type,
                            std::string_view name);

src/experimental/studio/index.html

@@ -7,7 +7,7 @@
   <body style="margin: 0; overflow: hidden">
     <div style="position: absolute; top: 3px; right: 3px; z-index: 1;">
       <button id="uploadButton">Upload Model</button>
-      <input type="file" id="fileInput" accept=".xml,.mjb" style="display: none;">
+      <input type="file" id="fileInput" accept=".xml,.mjb,.mjz,.zip" style="display: none;">
     </div>
     <canvas
       class="emscripten"

src/experimental/studio/wasm.cc

@@ -104,6 +104,10 @@ void LoadFile(const std::string& filename, const std::string& data) {
   std::string content_type;
   if (filename.ends_with(".mjb")) {
     content_type = "application/mjb";
+  } else if (filename.ends_with(".mjz")) {
+    content_type = "application/zip";
+  } else if (filename.ends_with(".zip")) {
+    content_type = "application/zip";
   } else if (filename.ends_with(".xml")) {
     content_type = "text/xml";
   } else {