Configure Copybara export for Dear ImGui and ImPlot Python bindings

Following the export declarations in Dear ImGui and ImPlot METADATA, this change updates MuJoCo's Copybara configuration (copy.bara.sky) to export and transform the Python bindings. `//third_party/dear_imgui/google/py` exports to `python/mujoco/experimental/dear_imgui` and `//third_party/implot/google/py` exports to  `python/mujoco/experimental/implot`.

PiperOrigin-RevId: 925293624
Change-Id: Ie6e32d247a6f7fc24bb36ae7060f2075d8efeb26

python/mujoco/experimental/studio/native_viewer.py

@@ -0,0 +1,171 @@
+# 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.
+"""Simulation-agnostic native viewer for MuJoCo models.
+
+This class is simulation-agnostic and as such it does not own the model or data.
+
+See the documentation for studio_app.py for more details on the architecture
+separating the viewer and simulation. See the sample/ folder for examples of how
+to use these classes.
+"""
+
+import mujoco
+
+from mujoco.experimental.studio import native_viewer_cc as _viewer
+from mujoco.experimental.studio import ux
+
+
+class NativeViewer:
+  """Simulation-agnostic native viewer for MuJoCo models."""
+
+  def __init__(
+      self,
+      model: mujoco.MjModel,
+      camera: mujoco.MjvCamera | None = None,
+      vis_options: mujoco.MjvOption | None = None,
+      perturb: mujoco.MjvPerturb | None = None,
+      render_flags: ux.RenderFlags | None = None,
+      title: str = '',
+      width: int = 1200,
+      height: int = 800,
+      gfx: str = '',
+  ) -> None:
+    """Initializes the NativeViewer.
+
+    The viewer creates and modifies its own camera, perturbation, and
+    visualization option objects unless they are provided.
+
+    Args:
+      model: The MuJoCo model, used to initialize the renderer.
+      camera: Camera parameters. Internal object is created if None.
+      vis_options: Visualization options. Internal object is created if None.
+      perturb: Perturbation parameters. Internal object is created if None.
+      render_flags: Render flags. Internal object is created if None.
+      title: Title of the viewer window.
+      width: Initial width of the viewer window.
+      height: Initial height of the viewer window.
+      gfx: Graphics mode.
+    """
+    self.camera = camera or mujoco.MjvCamera()
+    self.perturb = perturb or mujoco.MjvPerturb()
+    self.vis_options = vis_options or mujoco.MjvOption()
+    self._viewer = _viewer.Viewer(title, width, height, gfx)
+    self._viewer.InitRenderer(model)
+    # This class does not own the model but we need to know if the model being
+    # rendered has changed, so we store the unique python object id here so we
+    # can use it to detect model changes.
+    self._renderer_model_id = id(model)
+    self._is_running = True
+    if render_flags is not None:
+      self.render_flags = render_flags
+    else:
+      self.render_flags = ux.RenderFlags()
+      # Initted to match mujoco/src/engine/engine_vis_init.c
+      self.render_flags.flags = [1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1]
+
+  def _sync_renderer(self, model: mujoco.MjModel) -> None:
+    """Re-initializes the renderer if the model object has changed."""
+    if id(model) != self._renderer_model_id:
+      self._viewer.InitRenderer(model)
+      self._renderer_model_id = id(model)
+
+  def is_running(self) -> bool:
+    """Poll for a new frame; returns ``False`` when the window is closed."""
+    if not self._is_running:
+      return False
+    self._is_running = self._viewer.NewFrame()
+    return self._is_running
+
+  def sync(
+      self,
+      model: mujoco.MjModel,
+      data: mujoco.MjData,
+  ) -> None:
+    """Render the scene and present it to the window.
+
+    Args:
+      model: The MuJoCo model provided by the simulation.
+      data: The MuJoCo data provided by the simulation.
+    """
+    self._sync_renderer(model)
+    self._viewer.Present(
+        model,
+        data,
+        self.perturb,
+        self.camera,
+        self.vis_options,
+        self.render_flags.flags,
+    )
+
+  def stop(self) -> None:
+    """Stop the viewer."""
+    self._is_running = False
+
+  def get_drop_file(self) -> str:
+    """Returns the path of the file dropped into the window, or empty string."""
+    return self._viewer.GetDropFile()
+
+  def upload_image(
+      self, tex_id: int, img: str | bytes, width: int, height: int, bpp: int
+  ) -> int:
+    """Uploads an image to the backend for GUI rendering.
+
+    The ID can be used in subsequent calls to update the texture data. An empty
+    `img` argument will free the texture if it exists. A `tex_id` of 0 will
+    create a new texture.
+
+    Args:
+      tex_id: The texture ID.
+      img: The image data as string or bytes.
+      width: Width of the image.
+      height: Height of the image.
+      bpp: Bytes per pixel.
+
+    Returns:
+      The texture ID.
+    """
+    return self._viewer.UploadImage(tex_id, img, width, height, bpp)
+
+  def render_to_texture(
+      self,
+      model: mujoco.MjModel,
+      data: mujoco.MjData,
+      tex_id: int,
+      width: int,
+      height: int,
+  ) -> int:
+    """Renders the scene to a texture.
+
+    This function renders the scene from the current camera view into a texture.
+    It handles buffer allocation internally.
+
+    Args:
+      model: The MuJoCo model provided by the simulation.
+      data: The MuJoCo data provided by the simulation.
+      tex_id: The texture ID to render into (0 to create a new one).
+      width: Width of the texture.
+      height: Height of the texture.
+
+    Returns:
+      The texture ID.
+    """
+    self._sync_renderer(model)
+    return self._viewer.RenderToTexture(
+        model,
+        data,
+        self.camera,
+        width,
+        height,
+        tex_id,
+    )