No-op implementation for mjr_ functions.

This can be useful, e.g. writing tests that don't depend on rendering.

PiperOrigin-RevId: 879012859
Change-Id: Ifb8d7d5bb06a2456c1b4543f0bf4945fe8155039

src/render/noop/CMakeLists.txt

@@ -0,0 +1,15 @@
+# Copyright 2026 DeepMind Technologies Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+target_sources(mujoco PRIVATE render_noop.c)

src/render/noop/render_noop.c

@@ -0,0 +1,110 @@
+// Copyright 2026 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <mujoco/mujoco.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
+// library) when you do not intend to use any graphics APIs and want to reduce
+// dependencies, compile times, binary size, etc.
+
+void mjr_defaultContext(mjrContext* con) {
+  mju_error("mjr_defaultContext not implemented.");
+}
+void mjr_makeContext(const mjModel* m, mjrContext* con, int fontscale) {
+  mju_error("mjr_makeContext not implemented.");
+}
+void mjr_freeContext(mjrContext* con) {
+  mju_error("mjr_freeContext not implemented.");
+}
+void mjr_render(mjrRect viewport, mjvScene* scn, const mjrContext* con) {
+  mju_error("mjr_render not implemented.");
+}
+void mjr_uploadMesh(const mjModel* m, const mjrContext* con, int meshid) {
+  mju_error("mjr_uploadMesh not implemented.");
+}
+void mjr_uploadTexture(const mjModel* m, const mjrContext* con, int texid) {
+  mju_error("mjr_uploadTexture not implemented.");
+}
+void mjr_uploadHField(const mjModel* m, const mjrContext* con, int hfieldid) {
+  mju_error("mjr_uploadHField not implemented.");
+}
+void mjr_setBuffer(int framebuffer, mjrContext* con) {
+  mju_error("mjr_setBuffer not implemented.");
+}
+void mjr_readPixels(unsigned char* rgb, float* depth, mjrRect viewport,
+                          const mjrContext* con) {
+  mju_error("mjr_readPixels not implemented.");
+}
+void mjr_setAux(int index, const mjrContext* con) {
+  mju_error("mjr_setAux not implemented.");
+}
+void mjr_restoreBuffer(const mjrContext* con) {
+  mju_error("mjr_restoreBuffer not implemented.");
+}
+void mjr_rectangle(mjrRect viewport, float r, float g, float b, float a) {
+  mju_error("mjr_rectangle not implemented.");
+}
+void mjr_blitAux(int index, mjrRect src, int left, int bottom,
+                 const mjrContext* con) {
+  mju_error("mjr_blitAux not implemented.");
+}
+void mjr_changeFont(int fontscale, mjrContext* con) {
+  mju_error("mjr_changeFont not implemented.");
+}
+void mjr_addAux(int index, int width, int height, int samples,
+                mjrContext* con) {
+  mju_error("mjr_addAux not implemented.");
+}
+void mjr_resizeOffscreen(int width, int height, mjrContext* con) {
+  mju_error("mjr_resizeOffscreen not implemented.");
+}
+void mjr_drawPixels(const unsigned char* rgb, const float* depth,
+                    mjrRect viewport, const mjrContext* con) {
+  mju_error("mjr_drawPixels not implemented.");
+}
+void mjr_blitBuffer(mjrRect src, mjrRect dst, int flg_color, int flg_depth,
+                    const mjrContext* con) {
+  mju_error("mjr_blitBuffer not implemented.");
+}
+void mjr_text(int font, const char* txt, const mjrContext* con, float x,
+              float y, float r, float g, float b) {
+  mju_error("mjr_text not implemented.");
+}
+void mjr_overlay(int font, int gridpos, mjrRect viewport, const char* overlay,
+                 const char* overlay2, const mjrContext* con) {
+  mju_error("mjr_overlay not implemented.");
+}
+void mjr_label(mjrRect viewport, int font, const char* txt, float r, float g,
+               float b, float a, float rt, float gt, float bt,
+               const mjrContext* con) {
+  mju_error("mjr_label not implemented.");
+}
+void mjr_figure(mjrRect viewport, mjvFigure* fig, const mjrContext* con) {
+  mju_error("mjr_figure not implemented.");
+}
+void mjr_finish() { mju_error("mjr_finish not implemented."); }
+int mjr_getError() {
+  mju_error("mjr_getError not implemented.");
+  return 0;
+}
+mjrRect mjr_maxViewport(const mjrContext* con) {
+  mju_error("mjr_maxViewport not implemented.");
+  mjrRect rect = {0, 0, 0, 0};
+  return rect;
+}
+int mjr_findRect(int x, int y, int nrect, const mjrRect* rect) {
+  mju_error("mjr_findRect not implemented.");
+  return 0;
+}