`innerText` is not supported in Firefox prior to v45. In most cases (at least
the ones we are interested in), `innerText` and `textContent` work equally well,
but `textContent` is more performant (as it doesn't require a reflow).
From [MDN][1] on the differences of `innerText` vs `textContent`:
> - [...]
> - `innerText` is aware of style and will not return the text of hidden
> elements, whereas `textContent` will.
> - As `innerText` is aware of CSS styling, it will trigger a reflow, whereas
> `textContent` will not.
> - [...]
[1]: https://developer.mozilla.org/en-US/docs/Web/API/Node/textContent#Differences_from_innerTextFixes#17585
* refactor(aio): use explicit CSS class for TOC container
This makes the styling less fragile to changes in the HTML
* fix(aio): schedule TocComponent.activeIndex updates via AsapScheduler
We use the `asap` scheduler because updates to `activeItemIndex` are triggered by DOM changes,
which, in turn, are caused by the rendering that happened due to a ChangeDetection.
Without asap, we would be updating the model while still in a ChangeDetection handler,
which is disallowed by Angular.
* refactor(aio): do not instantiate floating ToC if not displayed
* feat(aio): display the h1 at the top of the floating TOC
Closes#16900
* refactor(aio): combine the TOC booleans flags into a "type" state
* refactor(aio): remove unnecessary `hostElement` property
* fix(aio): ensure that transition works on TOC
* fix(aio): use strict equality in ToC template
- Use buttons for the TOC “Contents” label when embedded-and-expandable or TOC on the right to satisfy a11y.
- Add aria-pressed setting for the toggles in TOC and NavItem.
- Clicking the right panel TOC “Contents” button scrolls to top.
- When embedded use same rotating caret as sidebar
- When embedded and no secondaries, “Content” is just a label.
- Gray background for focused buttons rather than outline because can’t get carets to work with outline.
By reflex we began all component tests with an async `beforeEach` that called `compileComponents`.
In at least one case (`live-example.component.spec.ts`) that led to the `it` tests being async as well.
There is no need to call `.compileComponents` because CLI web pack + plugin inlines all templates and styles.
While `.compileComponents` was harmless, it added complexity and distraction which we should not inflict on future readers and testers.
Previously the `hasToc` was initialised to true, which caused a flash of
unwanted "Contents" [sic] even if the page was not going to need a ToC.
Closes#16597
TOC appears in right panel when wide and hides embedded TOC
Right TOC panel height adjusts dynamically during scroll
Refactored `TocService` and its tests for clarity.
