Files
mkdocs-material/src/assets/javascripts/browser/element/offset/index.ts
2021-02-14 16:54:27 +01:00

106 lines
3.1 KiB
TypeScript

/*
* Copyright (c) 2016-2021 Martin Donath <martin.donath@squidfunk.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
import { Observable, fromEvent, merge } from "rxjs"
import { distinctUntilChanged, map, startWith } from "rxjs/operators"
import { getElementContentSize, getElementSize } from "../size"
/* ----------------------------------------------------------------------------
* Types
* ------------------------------------------------------------------------- */
/**
* Element offset
*/
export interface ElementOffset {
x: number /* Horizontal offset */
y: number /* Vertical offset */
}
/* ----------------------------------------------------------------------------
* Functions
* ------------------------------------------------------------------------- */
/**
* Retrieve element offset
*
* @param el - Element
*
* @returns Element offset
*/
export function getElementOffset(el: HTMLElement): ElementOffset {
return {
x: el.scrollLeft,
y: el.scrollTop
}
}
/* ------------------------------------------------------------------------- */
/**
* Watch element offset
*
* @param el - Element
*
* @returns Element offset observable
*/
export function watchElementOffset(
el: HTMLElement
): Observable<ElementOffset> {
return merge(
fromEvent(el, "scroll"),
fromEvent(window, "resize")
)
.pipe(
map(() => getElementOffset(el)),
startWith(getElementOffset(el))
)
}
/**
* Watch element threshold
*
* This function returns an observable which emits whether the bottom scroll
* offset of an elements is within a certain threshold.
*
* @param el - Element
* @param threshold - Threshold
*
* @returns Element threshold observable
*/
export function watchElementThreshold(
el: HTMLElement, threshold = 16
): Observable<boolean> {
return watchElementOffset(el)
.pipe(
map(({ y }) => {
const visible = getElementSize(el)
const content = getElementContentSize(el)
return y >= (
content.height - visible.height - threshold
)
}),
distinctUntilChanged()
)
}