mirror of
https://github.com/squidfunk/mkdocs-material.git
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132 lines
3.6 KiB
TypeScript
132 lines
3.6 KiB
TypeScript
/*
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* Copyright (c) 2016-2023 Martin Donath <martin.donath@squidfunk.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to
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* deal in the Software without restriction, including without limitation the
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* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*/
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import {
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NEVER,
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Observable,
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Subject,
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defer,
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distinctUntilChanged,
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filter,
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finalize,
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map,
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merge,
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of,
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shareReplay,
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switchMap,
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tap
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} from "rxjs"
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import {
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getElementContentSize,
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getElementSize,
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watchElementContentOffset
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} from "~/browser"
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/* ----------------------------------------------------------------------------
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* Data
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* ------------------------------------------------------------------------- */
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/**
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* Intersection observer entry subject
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*/
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const entry$ = new Subject<IntersectionObserverEntry>()
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/**
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* Intersection observer observable
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*
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* This observable will create an `IntersectionObserver` on first subscription
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* and will automatically terminate it when there are no more subscribers.
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*
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* @see https://bit.ly/3iIYfEm - Google Groups on performance
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*/
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const observer$ = defer(() => of(
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new IntersectionObserver(entries => {
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for (const entry of entries)
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entry$.next(entry)
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}, {
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threshold: 0
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})
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))
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.pipe(
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switchMap(observer => merge(NEVER, of(observer))
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.pipe(
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finalize(() => observer.disconnect())
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)
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),
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shareReplay(1)
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)
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/* ----------------------------------------------------------------------------
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* Functions
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* ------------------------------------------------------------------------- */
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/**
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* Watch element visibility
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*
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* @param el - Element
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*
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* @returns Element visibility observable
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*/
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export function watchElementVisibility(
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el: HTMLElement
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): Observable<boolean> {
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return observer$
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.pipe(
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tap(observer => observer.observe(el)),
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switchMap(observer => entry$
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.pipe(
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filter(({ target }) => target === el),
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finalize(() => observer.unobserve(el)),
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map(({ isIntersecting }) => isIntersecting)
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)
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)
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)
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}
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/**
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* Watch element boundary
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*
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* This function returns an observable which emits whether the bottom content
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* boundary (= scroll offset) of an element is within a certain threshold.
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*
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* @param el - Element
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* @param threshold - Threshold
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*
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* @returns Element boundary observable
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*/
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export function watchElementBoundary(
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el: HTMLElement, threshold = 16
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): Observable<boolean> {
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return watchElementContentOffset(el)
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.pipe(
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map(({ y }) => {
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const visible = getElementSize(el)
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const content = getElementContentSize(el)
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return y >= (
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content.height - visible.height - threshold
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)
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}),
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distinctUntilChanged()
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)
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}
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