Don't request data in WP dashboard widget when hidden

Feature Description

When connected, Site Kit adds a widget to the WordPress dashboard which is the default landing view for all users after logging in to wp-admin. These widgets can be hidden using user-specific screen options.

When hidden, the Site Kit widget is still rendered (because the hiding is CSS only) so requests for data are still made. We should update our WP dashboard widget component to only request data when not hidden. Apart from the screen option, the widget could also be off screen on mobile where it may be a better experience to lazy load the data as well.

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Acceptance criteria

• The WP dashboard widget should use the new useInViewSelect hook from #4096 for all of its API-based selector calls, replacing useSelect for those.
• The result should be that these API requests are only made when the WP dashboard widget is in or close to the viewport. The best way to test it is to hide the widget entirely via screen options. In that case, no API requests should be made.
  • When testing, please ensure to always clear your browser cache, since API requests are only made when nothing is cached yet.

Implementation Brief

• When #4096 has been merged, update all use of useSelect by useInViewSelect in assets/js/components/wp-dashboard/*.js

Test Coverage

• No new tests to be added. Existing tests that check the WP Dashboard widget output (E2E tests, mostly), may need to be updated to scroll to the WP Dashboard widget element to ensure it loads.

Visual Regression Changes

QA Brief

Changelog entry

[felixarntz]

Moving this to “Backlog” for now, since it will depend on the useInViewportSelect (or whatever that will be called) utility that we’ll only introduce as part of the unified dashboard epic.

[felixarntz]

Closing this since it’s now encompassed in #4096.