[examples] Drop CI requirement for DISPLAY

.bazelrc

@@ -5,10 +5,6 @@ common --keep_going=yes
 build --test_output=errors
 build --test_summary=terse
 
-# Inject DISPLAY into test runner environment for tests that use X.
-build --test_env=DISPLAY
-build --sandbox_add_mount_pair=/tmp/.X11-unix
-
 # Add `bazel test --config=lint` shortcut for linting.
 build:lint --test_tag_filters=lint
 

.github/ci_setup.bash

@@ -2,25 +2,4 @@
 
 set -euxo pipefail
 
-# Downgrade mesa per https://github.com/RobotLocomotion/drake/issues/18726.
-sudo apt-get --assume-yes --allow-downgrades install \
- xvfb \
- libegl1 \
- libegl-mesa0=22.0.1-1ubuntu2 \
- libgbm1=22.0.1-1ubuntu2 \
- libgl1-mesa-dri=22.0.1-1ubuntu2 \
- libglapi-mesa=22.0.1-1ubuntu2 \
- libglx-mesa0=22.0.1-1ubuntu2
-
-cat << EOF | sudo tee /lib/systemd/system/xvfb.service
-[Unit]
-After=network.target
-
-[Service]
-ExecStart=/usr/bin/Xvfb :99 -screen 0 1280x1024x24 -ac +extension GLX +extension RANDR +render -noreset
-
-[Install]
-WantedBy=multi-user.target
-EOF
-
-sudo systemctl --now --quiet enable /lib/systemd/system/xvfb.service
+sudo apt-get --assume-yes install libegl1

.github/workflows/main.yml

@@ -10,10 +10,6 @@ on:
     branches:
       - main
 
-env:
-  # Always use the Xvfb service's display.
-  DISPLAY: ":99"
-
 jobs:
   bazel_test:
     runs-on: ubuntu-latest
@@ -76,6 +72,13 @@ jobs:
         run: |
           ln -s .github/ci.bazelrc user.bazelrc
           ./bazel test //...
+      # Save the test outputs to allow for eyeball verification when relevant.
+      - name: Archive test outputs
+        uses: actions/upload-artifact@v4
+        with:
+          name: test_outputs
+          path: |
+            .bazel/testlogs/examples/ball_bin_test/test.outputs/outputs.zip
       # Save the updated cache snapshots, so we never do the same work twice.
       # By default, actions/cache only saves after a successful workflow, but
       # our caches are bags of files where we only ever add new files (not change

examples/ball_bin.yaml

@@ -60,8 +60,10 @@ cameras:
   vtk_camera:
     name: vtk_camera
     renderer_name: vtk
-    renderer_class: !RenderEngineVtkParams {}
-    show_rgb: True  # Use a live on-screen preview.
+    renderer_class: !RenderEngineVtkParams
+      backend: EGL
+    # For `show_rgb: True` you must also set the `backend: GLX` on prior line.
+    show_rgb: False
     width: 1024
     height: 1024
     fps: 8.0

examples/test/ball_bin_test.py

@@ -13,6 +13,9 @@ def setUp(self):
         self.tmpdir = Path(os.environ["TEST_TMPDIR"])
         self.assertTrue(self.tmpdir.exists(), self.tmpdir)
 
+        self.out_dir = Path(os.environ["TEST_UNDECLARED_OUTPUTS_DIR"])
+        self.assertTrue(self.out_dir.exists(), self.out_dir)
+
         # Find the demo.
         demo_path = Path("examples/ball_bin").absolute().resolve()
         self.assertTrue(demo_path.exists(), demo_path)
@@ -71,21 +74,21 @@ def test_still_images(self):
             f"--scenario_file={scenario_file}",
         ]
 
-        result = subprocess.run(run_args, cwd=self.tmpdir)
+        result = subprocess.run(run_args, cwd=self.out_dir)
         result.check_returncode()
-        self.assertTrue((self.tmpdir / "vtk_camera.png").exists())
-        self.assertTrue((self.tmpdir / "blender_camera.png").exists())
+        self.assertTrue((self.out_dir / "vtk_camera.png").exists())
+        self.assertTrue((self.out_dir / "blender_camera.png").exists())
 
     def test_video(self):
         """Checks that the example creates 2x video files."""
         scenario_file = self._get_scenario_file(nerf_scenario=True)
 
         run_args = self.default_run_args + [f"--scenario_file={scenario_file}"]
 
-        result = subprocess.run(run_args, cwd=self.tmpdir)
+        result = subprocess.run(run_args, cwd=self.out_dir)
         result.check_returncode()
-        self.assertTrue((self.tmpdir / "vtk_camera.mp4").exists())
-        self.assertTrue((self.tmpdir / "blender_camera.mp4").exists())
+        self.assertTrue((self.out_dir / "vtk_camera.mp4").exists())
+        self.assertTrue((self.out_dir / "blender_camera.mp4").exists())
 
 
 if __name__ == "__main__":