Adding Doc Snippets

Adding Doc Snippets

Overview

Every substantial code example in the ovrtx docs must be backed by a tested snippet. This skill walks through the full workflow from writing the test to wiring up the RST.

Step 1: Decide where the test goes

Keep usd-core imports in tests/docs/usd/ unless a snippet explicitly needs to demonstrate OpenUSD interop with ovrtx; this keeps the ovrtx runtime tests from picking up docs-only USD dependencies.

Step 2: Write the test with snippet markers

For ovrtx Python snippets

Create or edit a test file in tests/docs/python/. The test function handles setup (loading scenes, warm-up steps), and the snippet markers wrap only the code the reader should see:

@pytest.mark.usd_scene("simple_camera.usda")
def test_my_feature(renderer, usd_scene):
    """Test description matching the doc section."""
    # Setup -- not in snippet
    renderer.open_usd_from_string(_make_scene(str(usd_scene)))
    for _ in range(5):
        renderer.step(render_products={"/Render/Camera"}, delta_time=1/60)

    # [snippet:doc-my-feature]
    products = renderer.step(
        render_products={"/Render/Camera"},
        delta_time=1.0 / 60,
    )
    for product_name, product in products.items():
        for frame in product.frames:
            var = frame.render_vars["LdrColor"].map(device=ovrtx.Device.CPU)
            pixels = np.from_dlpack(var)
            assert pixels.shape[2] == 4
    # [/snippet:doc-my-feature]

Key points:

• Snippet markers wrap only the doc-visible code -- setup and assertions stay outside.
• Use ovrtx.Device.CPU (not Device.CPU or "cpu") so the snippet is self-explanatory without a visible import.
• Scene loading uses the sublayer pattern (see skills/sublayer-test-scenes/SKILL.md).

For USDA data files

Create a .usda file in tests/docs/usd/data/ with snippet markers using # comments:

#usda 1.0

# [snippet:doc-my-render-product]
def "Render" {
    def RenderProduct "Camera" {
        rel camera = </World/Camera>
        rel orderedVars = [<LdrColor>]

        def RenderVar "LdrColor" {
            string sourceName = "LdrColor"
        }
    }
}
# [/snippet:doc-my-render-product]

Then add a validation test in tests/docs/usd/test_*_usda.py:

def test_my_render_product():
    usda_text = (DATA_DIR / "my_file.usda").read_text()
    layer = validate_usda(usda_text)
    assert layer.GetPrimAtPath("/Render/Camera")

For USD Python API tabs

Add a test to tests/docs/usd/test_usd_python_examples.py. The CreateInMemory() call stays outside the snippet markers -- it's setup:

def test_my_render_product():
    stage = Usd.Stage.CreateInMemory()

    # [snippet:doc-my-render-product-python]
    render_scope = stage.DefinePrim("/Render")
    camera_product = UsdRender.Product.Define(stage, "/Render/Camera")
    camera_product.GetCameraRel().SetTargets(["/World/Camera"])
    # ... etc
    # [/snippet:doc-my-render-product-python]

    assert stage.GetPrimAtPath("/Render/Camera").IsValid()

Step 3: Wire up the RST

USDA blocks become tab-sets with USDA + Python tabs

.. tab-set::

   .. tab-item:: USDA

      .. literalinclude:: ../tests/docs/usd/data/my_file.usda
         :language: usda
         :start-after: # [snippet:doc-my-render-product]
         :end-before: # [/snippet:doc-my-render-product]

   .. tab-item:: Python

      .. literalinclude:: ../tests/docs/usd/test_usd_python_examples.py
         :language: python
         :start-after: # [snippet:doc-my-render-product-python]
         :end-before: # [/snippet:doc-my-render-product-python]
         :dedent:

Python/C runtime code uses existing tab-sets

.. tab-set::

   .. tab-item:: Python

      .. literalinclude:: ../tests/docs/python/test_something.py
         :language: python
         :start-after: # [snippet:doc-my-feature]
         :end-before: # [/snippet:doc-my-feature]
         :dedent:

   .. tab-item:: C

      .. literalinclude:: ../tests/docs/c/test_something.cpp
         :language: cpp
         :start-after: // [snippet:doc-my-feature-c]
         :end-before: // [/snippet:doc-my-feature-c]
         :dedent:

Step 4: Run the tests

cd tests/docs/usd && uv run pytest -v        # USDA + USD Python API
cd tests/docs/python && uv run pytest -v      # ovrtx (needs GPU)
cd tests/docs/c && cmake -B build-dev -DCMAKE_PREFIX_PATH=/path/to/ovrtx && cmake --build build-dev && ctest --test-dir build-dev --output-on-failure

Step 5: Update the snippet inventory

Add new snippets to the table in tests/docs/AGENTS.md so others can find them.

Style Rules for Prose

Function names always get parentheses

When mentioning a function or method in prose, always include trailing parentheses so it reads as a callable:

• Good: write_array_attribute()
• Bad: write_array_attribute

Link function names to API docs

When referencing ovrtx functions in RST prose, use Sphinx cross-reference roles so the reader can click through to the full API documentation:

Python -- use :py:meth: for Renderer methods, :py:func: for free functions, :py:class: for classes:

Use :py:meth:`~ovrtx.Renderer.write_array_attribute()` to write array data.

The ~ prefix displays only the method name (write_array_attribute()) rather than the fully qualified path. Without it you get ovrtx.Renderer.write_array_attribute().

C -- use :c:func: for C API functions:

Use :c:func:`ovrtx_set_path_attributes()` to write path attributes.

These roles will generate hyperlinks when the target exists in the autodoc/breathe output. If the target doesn't exist (e.g., a static inline helper not in a doxygen group), the text still renders as styled monospace, so there's no downside to using them.

Common Pitfalls

• Don't forget :dedent: on Python literalincludes. Without it the code renders with test-level indentation.
• Snippet names must be globally unique across all files in tests/docs/.
• Don't include setup in snippets. CreateInMemory(), warm-up loops, scene loading -- these are test infrastructure, not doc content.
• Always use the doc- prefix for snippet names in this tree so doc-tested snippets are easy to identify in skills and RST.
• Always include parentheses on function names in prose text -- write_array_attribute() not write_array_attribute.
• Always use cross-reference roles (:py:meth:, :c:func:, etc.) for ovrtx API functions in RST prose, not bare double-backtick literals.