Facets Dive - Instructions for setting atlasUrl are underspecified

[jimbojw]

The instructions in the Facets Dive README.md state:

To specify the URL to an atlas to use, set the atlasUrl property of the Dive Polymer Element in JavaScript (or the atlas-url attribute in HTML).

This is insufficient. The distinction between atlasUrl and atlas-url should be made more clear by example. The README.md file should include this JS snippet to showcase the atlasUrl property:

const vis = document.querySelector('facets-dive');
vis.atlasUrl = 'your_sprite_image.png';

That file should also show this HTML snippet for the atlas-url attribute:

<facets-dive atlas-url="your_sprite_image.png"></facets-dive>

To serve the sprite atlas image from the bazel test server, you have to include it as a source in the test target of the BUILD file.

ts_web_library(
    name = "test",
    testonly = True,
    srcs = [
        "test.html",
        "test.ts",
        "your_sprite_image.png",  ### ADD THIS ###
    ],
    path = "/facets-dive/components/facets-dive",
    deps = [
        ":facets_dive",
        "//facets_dive/lib/test:externs",
        "@org_tensorflow_tensorboard//tensorboard/components/tf_imports:web_component_tester",
    ],
)