docs(python): add example_add_cube example

python/examples/example_add_cube.py

@@ -0,0 +1,56 @@
+import argparse
+
+import neuroglancer
+import neuroglancer.cli
+import neuroglancer.random_token
+
+if __name__ == "__main__":
+    cube_size_meters = 10e-6
+
+    ap = argparse.ArgumentParser()
+    neuroglancer.cli.add_server_arguments(ap)
+    args = ap.parse_args()
+    neuroglancer.cli.handle_server_arguments(args)
+    viewer = neuroglancer.Viewer()
+
+    def add_cube(s):
+        with viewer.txn() as state:
+            scale = state.dimensions.scales
+            center_point = s.mouse_voxel_coordinates * scale / 1e-9
+            point_a = center_point
+            layer = state.layers["annotations"]
+            layer.annotations.append(
+                neuroglancer.AxisAlignedBoundingBoxAnnotation(
+                    id=neuroglancer.random_token.make_random_token(),
+                    point_a=center_point - cube_size_meters * 1e9,
+                    point_b=center_point + cube_size_meters * 1e9,
+                )
+            )
+
+    viewer.actions.add("add-cube", add_cube)
+    with viewer.config_state.txn() as s:
+        s.input_event_bindings.viewer["keyt"] = "add-cube"
+
+    with viewer.txn() as s:
+        s.dimensions = neuroglancer.CoordinateSpace(
+            names=["x", "y", "z"],
+            units="nm",
+            scales=[8, 8, 8],
+        )
+        s.layers.append(
+            name="image",
+            layer=neuroglancer.ImageLayer(
+                source="precomputed://gs://neuroglancer-public-data/flyem_fib-25/image",
+            ),
+        )
+        s.layers.append(
+            name="annotations",
+            layer=neuroglancer.LocalAnnotationLayer(
+                dimensions=neuroglancer.CoordinateSpace(
+                    names=["x", "y", "z"],
+                    units="nm",
+                    scales=[1, 1, 1],
+                ),
+            ),
+        )
+    print(viewer)