Add renderer info query API

src/render/classic/render_context.c

@@ -55,6 +55,30 @@ void mjr_defaultContext(mjrContext* con) {
   memset(con, 0, sizeof(mjrContext));
 }
 
+static int context_count = 0;
+
+static int contextHasResources(const mjrContext* con) {
+  return con->ntexture || con->offColor || con->offDepthStencil || con->offFBO ||
+         con->shadowTex || con->shadowFBO || con->rangePlane || con->rangeMesh ||
+         con->rangeHField || con->rangeBuiltin || con->rangeFont || con->nskin;
+}
+
+// set default mjrRendererInfo
+void mjr_defaultRendererInfo(mjrRendererInfo* info) {
+  memset(info, 0, sizeof(mjrRendererInfo));
+  info->renderer = "classic";
+  info->backend = "";
+  info->backend_version = "";
+}
+
+// get active renderer information
+void mjr_getRendererInfo(mjrRendererInfo* info) {
+  mjr_defaultRendererInfo(info);
+  if (context_count > 0) {
+    info->backend = "opengl";
+  }
+}
+
 
 
 // allocate lists
@@ -1608,6 +1632,7 @@ void mjr_makeContext_offSize(const mjModel* m, mjrContext* con, int fontscale,
     // try to bind window (bind offscreen if no window)
     mjr_setBuffer(mjFB_WINDOW, con);
 
+    context_count++;
     return;
   }
 
@@ -1667,6 +1692,7 @@ void mjr_makeContext_offSize(const mjModel* m, mjrContext* con, int fontscale,
 
   // set default depth mapping for mjr_readPixels
   con->readDepthMap = mjDEPTH_ZERONEAR;
+  context_count++;
 }
 
 
@@ -1811,6 +1837,8 @@ void mjr_addAux(int index, int width, int height, int samples, mjrContext* con)
 
 // free resources in custom OpenGL context
 void mjr_freeContext(mjrContext* con) {
+  int had_resources = contextHasResources(con);
+
   // save flags
   int glInitialized = con->glInitialized;
   int windowAvailable = con->windowAvailable;
@@ -1867,6 +1895,10 @@ void mjr_freeContext(mjrContext* con) {
   con->windowSamples = windowSamples;
   con->windowStereo = windowStereo;
   con->windowDoublebuffer = windowDoublebuffer;
+
+  if (had_resources && context_count > 0) {
+    context_count--;
+  }
 }
 
 

src/render/filament/core/filament_context.cc

@@ -49,6 +49,7 @@ namespace mujoco {
 FilamentContext::FilamentContext(const mjrfContextConfig* config)
     : config_(*config) {
   FilamentPlatformSetup setup = CreateFilamentPlatform(config_);
+  backend_ = setup.backend;
   platform_ = std::move(setup.platform);
 
   filament::Engine::Config engine_config;
@@ -58,7 +59,7 @@ FilamentContext::FilamentContext(const mjrfContextConfig* config)
 
   filament::Engine::Builder engine_builder;
   engine_builder.config(&engine_config);
-  engine_builder.backend(setup.backend);
+  engine_builder.backend(backend_);
   engine_builder.platform(platform_.get());
   engine_builder.feature("backend.disable_parallel_shader_compile",
                          setup.disable_parallel_shader_compile);

src/render/filament/core/filament_context.h

@@ -59,6 +59,8 @@ class FilamentContext : public mjrfContext {
 
   filament::Engine* GetEngine() const { return engine_; }
 
+  filament::Engine::Backend GetBackend() const { return backend_; }
+
   ObjectManager* GetObjectManager() const { return object_manager_.get(); }
 
   MaterialManager* GetMaterialManager() const {
@@ -76,6 +78,7 @@ class FilamentContext : public mjrfContext {
   void ValidateSwapChains(std::span<const mjrfRenderRequest> render_requests);
 
   mjrfContextConfig config_;
+  filament::Engine::Backend backend_;
   filament::Engine* engine_ = nullptr;
   filament::Renderer* renderer_ = nullptr;
   filament::SwapChain* window_swap_chain_ = nullptr;

src/render/filament/mjrfilament.cc

@@ -37,6 +37,17 @@ static void setf(float (&arr)[N], const std::array<float, N>& values) {
   }
 }
 
+static const char* BackendName(filament::Engine::Backend backend) {
+  switch (backend) {
+    case filament::Engine::Backend::OPENGL:
+      return "opengl";
+    case filament::Engine::Backend::VULKAN:
+      return "vulkan";
+    default:
+      return "unknown";
+  }
+}
+
 extern "C" {
 
 void mjrf_defaultContextConfig(mjrfContextConfig* config) {
@@ -124,6 +135,13 @@ void mjrf_destroyContext(mjrfContext* ctx) {
   delete mujoco::FilamentContext::downcast(ctx);
 }
 
+void mjrf_getRendererInfo(mjrfContext* ctx, mjrRendererInfo* info) {
+  memset(info, 0, sizeof(mjrRendererInfo));
+  info->renderer = "filament";
+  info->backend = ctx ? BackendName(mujoco::FilamentContext::downcast(ctx)->GetBackend()) : "";
+  info->backend_version = "";
+}
+
 mjrfTexture* mjrf_createTexture(mjrfContext* ctx,
                                 const mjrfTextureConfig* config) {
   return new mujoco::Texture(

src/render/noop/render_noop.c

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include <mujoco/mujoco.h>
+#include <string.h>
 
 // This library implements the entirety of mujoco's mjr API as fast-fail stubs.
 // You can link this library with your application (instead of standard renderer
@@ -22,6 +23,15 @@
 void mjr_defaultContext(mjrContext* con) {
   mju_error("mjr_defaultContext not implemented.");
 }
+void mjr_defaultRendererInfo(mjrRendererInfo* info) {
+  memset(info, 0, sizeof(mjrRendererInfo));
+  info->renderer = "noop";
+  info->backend = "";
+  info->backend_version = "";
+}
+void mjr_getRendererInfo(mjrRendererInfo* info) {
+  mjr_defaultRendererInfo(info);
+}
 void mjr_makeContext(const mjModel* m, mjrContext* con, int fontscale) {
   mju_error("mjr_makeContext not implemented.");
 }