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* @module Utils
*/
import * as MC from "@lisn/globals/minification-constants";
import * as MH from "@lisn/globals/minification-helpers";
import { settings } from "@lisn/globals/settings";
import {
ScrollDirection,
ScrollTarget,
TargetCoordinates,
CoordinateOffset,
ScrollPosition,
Anchor,
} from "@lisn/globals/types";
import {
newAnimationFrameIterator,
ElapsedTimes,
} from "@lisn/utils/animations";
import { getComputedStylePropNow } from "@lisn/utils/css-alter";
import { SCROLL_DIRECTIONS } from "@lisn/utils/directions";
import {
waitForInteractive,
waitForElementOrInteractive,
} from "@lisn/utils/dom-events";
import { waitForMeasureTime } from "@lisn/utils/dom-optimize";
import { addEventListenerTo, removeEventListenerFrom } from "@lisn/utils/event";
import { logError, logWarn } from "@lisn/utils/log";
import { maxAbs, criticallyDamped } from "@lisn/utils/math";
import { randId, formatAsString } from "@lisn/utils/text";
import { isValidStrList } from "@lisn/utils/validation";
import { newXMap } from "@lisn/modules/x-map";
import debug from "@lisn/debug/debug";
/**
* @category Scrolling
*/
export type ScrollAction = {
cancel: () => boolean;
/**
* Will reject if the scroll is cancelled.
*/
waitFor: () => Promise<ScrollPosition>;
};
/**
* @category Scrolling
* @interface
*/
export type ScrollToOptions = {
/**
* The element that should be scrolled.
*
* @defaultValue If `document.body` is scrollable, will use that; otherwise `document.scrollingElement`
*/
scrollable?: Element;
/**
* Offset the target coordinates by the given amount(s).
*
* E.g. if the final target coordinates are computed to be
* `{top: 100, left: 0}` and you specify offset as `{top: 10, left: 20}`, it
* will scroll to `{top: 110, left: 20}`.
*
* @defaultValue undefined
*/
offset?: CoordinateOffset;
// TODO maybe support fixed average velocity as an alternative to fixed duration?
/**
* The duration of the scroll animation in milliseconds. If not given, it is
* instant.
*
* @defaultValue 0
*/
duration?: number;
/**
* Whether another request to us to scroll the same target can interrupt this
* scroll before it finishes.
*
* @defaultValue false
*/
weCanInterrupt?: boolean;
/**
* Whether a user attempt to scroll the target can interrupt this before it
* finishes.
*
* @defaultValue false
*/
userCanInterrupt?: boolean;
/**
* If the scrolling element is already at the given coordinates (or strictly
* speaking we allow for 5 pixels difference), then if `altTarget` is given,
* this will become the target to scroll to.
*
* @defaultValue undefined
*/
altTarget?: TargetCoordinates | Element | string;
/**
* Offset the target coordinates by the given amount(s) when `altTarget` is used.
*
* See {@link ScrollToOptions.offset}.
*
* @defaultValue undefined
*/
altOffset?: CoordinateOffset;
};
// ----------
/**
* Returns true if the given element is scrollable in the given direction, or
* in either direction (if `axis` is not given).
*
* It first checks whether the current scroll offset on the target along the
* given axis is non-0, and if so returns true immediately. Otherwise it will
* attempt to determine if it's scrollable using one of these methods
* (controlled by `options.active`):
* - passive check (default): Will examine `clientWidth/Height`,
* `scrollWidth/Height` as well as the computed `overflow` CSS property to try
* to determine if the target is scrollable. This is not 100% reliable but is
* safer than the active check
* - active check: Will attempt to scroll the target by 1px and examine if the
* scroll offset had changed, then revert it back to 0. This is a more
* reliable check, however it can cause issues in certain contexts. In
* particular, if a scroll on the target had just been initiated (but it's
* scroll offset was still 0), the scroll may be cancelled. Never use that
* inside scroll-based handlers.
*
* **NOTE:** If the layout has been invalidated and not yet recalculated, this
* will cause a forced layout, so always {@link waitForMeasureTime} before
* calling this function when possible.
*
* @param [options.axis] One of "x" or "y" for horizontal or vertical scroll
* respectively. If not given, it checks both.
* @param [options.active] If true, then if the target's current scroll offset
* is 0, it will attempt to scroll it rather than
* looking at its overflow.
* @param [options.noCache] By default the result of a check is cached for 1s
* and if there's already a cached result for this
* element, it is returned. Set this to true to disable
* checking the cache and also saving the result into
* the cache.
*
* @category Scrolling
*/
export const isScrollable = (
element: Element,
options?: {
axis?: "x" | "y";
active?: boolean;
noCache?: boolean;
},
): boolean => {
const { axis, active, noCache } = options ?? {};
if (!axis) {
return (
isScrollable(element, { axis: "y", active, noCache }) ||
isScrollable(element, { axis: "x", active, noCache })
);
}
if (!noCache) {
const cachedResult = isScrollableCache.get(element)?.get(axis);
if (!MH.isNullish(cachedResult)) {
return cachedResult;
}
}
const offset = axis === "x" ? "Left" : "Top";
let result = false;
if (element[`scroll${offset}`]) {
result = true;
} else if (active) {
// Use scrollTo with explicit behavior set to instant instead of setting
// the scrollTop/Left properties since the latter doesn't work with
// scroll-behavior smooth.
MH.elScrollTo(element, { [MH.toLowerCase(offset)]: 1 });
const canScroll = element[`scroll${offset}`] > 0;
MH.elScrollTo(element, { [MH.toLowerCase(offset)]: 0 });
result = canScroll;
} else {
const dimension = axis === "x" ? "Width" : "Height";
const isDocScrollable = element === MH.getDocScrollingElement();
const hasOverflow =
element[`scroll${dimension}`] > element[`client${dimension}`];
const overflowProp = getComputedStylePropNow(element, "overflow");
const scrollingOverflows = [
MC.S_SCROLL,
MC.S_AUTO,
...(isDocScrollable ? [MC.S_VISIBLE] : []),
];
result = hasOverflow && MH.includes(scrollingOverflows, overflowProp);
}
if (!noCache) {
isScrollableCache.sGet(element).set(axis, result);
MH.setTimer(() => {
MH.deleteKey(isScrollableCache.get(element), axis);
isScrollableCache.prune(element);
}, IS_SCROLLABLE_CACHE_TIMEOUT);
}
return result;
};
/**
* Returns the closest scrollable ancestor of the given element, _not including
* it_.
*
* @param options See {@link isScrollable}
*
* @returns `null` if no scrollable ancestors are found.
*
* @category Scrolling
*/
export const getClosestScrollable = (
element: Element,
options?: {
axis?: "x" | "y";
active?: boolean;
noCache?: boolean;
},
) => {
// Walk up the tree, starting at the element in question but excluding it.
let ancestor: Element | null | undefined = element;
while ((ancestor = MH.parentOf(ancestor))) {
if (isScrollable(ancestor, options)) {
return ancestor;
}
}
return null;
};
/**
* Returns the current {@link ScrollAction} if any.
*
* @category Scrolling
*/
export const getCurrentScrollAction = (
scrollable?: Element,
): ScrollAction | null => {
scrollable = toScrollableOrDefault(scrollable);
const info = currentScrollInfos.get(scrollable);
if (info) {
return MH.copyObject(info._action);
}
return null;
};
/**
* Scrolls the given scrollable element to the given `to` target.
*
* Returns `null` if there's an ongoing scroll that is not cancellable.
*
* Note that if `to` is an element or a query selector string, then it _must_ be
* a descendant of the scrollable element.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the target coordinates are invalid.
*
* @param to If this is an element, then its top-left position is used as
* the target coordinates. If it is a string, then it is treated
* as a selector for an element using `querySelector`.
*
* @returns `null` if there's an ongoing scroll that is not cancellable,
* otherwise a {@link ScrollAction}.
*
* @category Scrolling
*/
export const scrollTo = (
to: TargetCoordinates | Element | string,
userOptions?: ScrollToOptions,
): ScrollAction | null => {
const options = getOptions(to, userOptions);
const scrollable = options._scrollable;
// cancel current scroll action if any
const info = currentScrollInfos.get(scrollable);
if (info) {
if (!info._action.cancel()) {
// current scroll action is not cancellable by us
return null;
}
}
let isCancelled = false;
const cancelFn = options._weCanInterrupt
? () => (isCancelled = true)
: () => false;
const scrollEvents = ["touchmove", "wheel"]; // don't bother with keyboard
let preventScrollHandler: EventListener | null = null;
if (options._userCanInterrupt) {
for (const eventType of scrollEvents) {
addEventListenerTo(
scrollable,
eventType,
() => {
isCancelled = true;
},
{ once: true },
);
}
} else {
preventScrollHandler = MH.preventDefault;
for (const eventType of scrollEvents) {
addEventListenerTo(scrollable, eventType, preventScrollHandler, {
passive: false,
});
}
}
const thisInfo: ScrollInfo = {
_action: {
waitFor: () => scrollActionPromise,
cancel: cancelFn,
},
};
const cleanup = () => {
if (currentScrollInfos.get(scrollable)?._action === thisInfo._action) {
MH.deleteKey(currentScrollInfos, scrollable);
}
if (preventScrollHandler) {
for (const eventType of scrollEvents) {
removeEventListenerFrom(scrollable, eventType, preventScrollHandler, {
passive: false,
});
}
}
};
const scrollActionPromise = initiateScroll(options, () => isCancelled);
thisInfo._action.waitFor().then(cleanup).catch(cleanup);
updateCurrentScrollInfo(scrollable, thisInfo);
return thisInfo._action;
};
/**
* Returns true if the given string is a valid scroll direction.
*
* @category Validation
*/
export const isValidScrollDirection = (
direction: string,
): direction is ScrollDirection => MH.includes(SCROLL_DIRECTIONS, direction);
/**
* Returns true if the given string or array is a list of valid scroll
* directions.
*
* @category Validation
*/
export const isValidScrollDirectionList = (directions: string | string[]) =>
isValidStrList(directions, isValidScrollDirection, false);
/**
* @ignore
* @internal
*/
export const mapScrollable = (original: Element, actualScrollable: Element) =>
mappedScrollables.set(original, actualScrollable);
/**
* @ignore
* @internal
*/
export const unmapScrollable = (original: Element) =>
MH.deleteKey(mappedScrollables, original);
/**
* @ignore
* @internal
*/
export const getClientWidthNow = (element: Element) =>
isScrollableBodyInQuirks(element)
? element.offsetWidth -
getBorderWidth(element, MC.S_LEFT) -
getBorderWidth(element, MC.S_RIGHT)
: element[MC.S_CLIENT_WIDTH];
/**
* @ignore
* @internal
*/
export const getClientHeightNow = (element: Element) =>
isScrollableBodyInQuirks(element)
? element.offsetHeight -
getBorderWidth(element, MC.S_TOP) -
getBorderWidth(element, MC.S_BOTTOM)
: element[MC.S_CLIENT_HEIGHT];
/**
* @ignore
* @internal
*/
export const tryGetMainContentElement = (): HTMLElement | null =>
mainContentElement ?? null;
/**
* @ignore
* @internal
*
* Exposed via ScrollWatcher
*/
export const fetchMainContentElement = async (): Promise<HTMLElement> => {
await init();
return mainContentElement;
};
/**
* @ignore
* @internal
*/
export const tryGetMainScrollableElement = (): HTMLElement | null =>
mainScrollableElement ?? null;
/**
* @ignore
* @internal
*
* Exposed via ScrollWatcher
*/
export const fetchMainScrollableElement = async (): Promise<HTMLElement> => {
await init();
return mainScrollableElement;
};
/**
* @ignore
* @internal
*/
export const getDefaultScrollingElement = () => {
const body = MH.getBody();
return isScrollable(body) ? body : (MH.getDocScrollingElement() ?? body);
};
/**
* @ignore
* @internal
*/
export const tryGetScrollableElement = (
target: ScrollTarget | null | undefined,
): Element | null => toScrollableOrMain(target, tryGetMainScrollableElement);
/**
* @ignore
* @internal
*/
export const fetchScrollableElement = async (
target: ScrollTarget | null | undefined,
): Promise<Element> => toScrollableOrMain(target, fetchMainScrollableElement);
// ----------------------------------------
type ScrollToOptionsInternal = {
_target: TargetCoordinates;
_offset: CoordinateOffset | null;
_altTarget: TargetCoordinates | null;
_altOffset: CoordinateOffset | null;
_scrollable: Element;
_duration: number;
_weCanInterrupt: boolean;
_userCanInterrupt: boolean;
};
type Velocity = { top: number; left: number };
type ScrollInfo = {
_action: ScrollAction;
_position?: ScrollPosition;
_velocity?: Velocity;
_elapsed?: ElapsedTimes;
};
const IS_SCROLLABLE_CACHE_TIMEOUT = 1000;
const isScrollableCache = newXMap<Element, Map<"x" | "y", boolean>>(() =>
MH.newMap(),
);
const mappedScrollables = MH.newMap<Element, Element>();
const currentScrollInfos = MH.newMap<Element, ScrollInfo>();
const DIFF_THRESHOLD = 5;
const arePositionsDifferent = (
start: ScrollPosition,
end: ScrollPosition,
threshold = DIFF_THRESHOLD,
) => maxAbs(start.top - end.top, start.left - end.left) > threshold;
// must be called in "measure time"
const getBorderWidth = (element: Element, side: Anchor) =>
MH.ceil(MH.parseFloat(getComputedStylePropNow(element, `border-${side}`)));
const isScrollableBodyInQuirks = (element: Element): element is HTMLElement =>
element === MH.getBody() && MH.getDocScrollingElement() === null;
const toScrollableOrMain = <R>(
target: ScrollTarget | null | undefined,
getMain: () => R,
): Element | R => {
if (MH.isElement(target)) {
return mappedScrollables.get(target) ?? target;
}
if (!target || target === MH.getWindow() || target === MH.getDoc()) {
return getMain();
}
throw MH.usageError("Unsupported scroll target");
};
const toScrollableOrDefault = (scrollable: Element | undefined): Element =>
scrollable ?? getDefaultScrollingElement();
const getOptions = (
to: TargetCoordinates | Element | string,
options: ScrollToOptions | undefined,
): ScrollToOptionsInternal => {
const scrollable = toScrollableOrDefault(options?.scrollable);
const target = getTargetCoordinates(scrollable, to);
const altTarget = options?.altTarget
? getTargetCoordinates(scrollable, options?.altTarget)
: null;
return {
_target: target,
_offset: options?.offset ?? null,
_altTarget: altTarget,
_altOffset: options?.altOffset ?? null,
_scrollable: scrollable,
_duration: options?.duration ?? 0,
_weCanInterrupt: options?.weCanInterrupt ?? false,
_userCanInterrupt: options?.userCanInterrupt ?? false,
};
};
const updateCurrentScrollInfo = (
scrollable: Element,
newInfo: Partial<ScrollInfo>,
) => {
const existingScrollInfo = currentScrollInfos.get(scrollable);
const _action = newInfo._action ?? existingScrollInfo?._action;
if (_action) {
currentScrollInfos.set(
scrollable,
MH.merge(existingScrollInfo, newInfo, { _action }),
);
}
};
const getTargetCoordinates = (
scrollable: Element,
target: TargetCoordinates | Element | string,
): TargetCoordinates => {
const isDocScrollingElement = scrollable === MH.getDocScrollingElement();
if (MH.isElement(target)) {
if (scrollable === target || !scrollable.contains(target)) {
throw MH.usageError("Target must be a descendant of the scrollable one");
}
return {
top: () =>
MH.getBoundingClientRect(target).top -
MH.getBoundingClientRect(scrollable).top +
(isDocScrollingElement ? 0 : scrollable[MC.S_SCROLL_TOP]),
left: () =>
MH.getBoundingClientRect(target).left -
MH.getBoundingClientRect(scrollable).left +
(isDocScrollingElement ? 0 : scrollable[MC.S_SCROLL_LEFT]),
};
}
if (MH.isString(target)) {
const targetEl = MH.docQuerySelector(target);
if (!targetEl) {
throw MH.usageError(`No match for '${target}'`);
}
return getTargetCoordinates(scrollable, targetEl);
}
if (!MH.isObject(target) || !("top" in target || "left" in target)) {
throw MH.usageError("Invalid coordinates");
}
return target;
};
const getStartEndPosition = async (
options: ScrollToOptionsInternal,
): Promise<{ _start: ScrollPosition; _end: ScrollPosition }> => {
await waitForMeasureTime();
const applyOffset = (
position: ScrollPosition,
offset: CoordinateOffset | null,
) => {
position.top += offset?.top ?? 0;
position.left += offset?.left ?? 0;
};
const scrollable = options._scrollable;
const start = {
top: scrollable[MC.S_SCROLL_TOP],
left: scrollable[MC.S_SCROLL_LEFT],
};
let end = getEndPosition(scrollable, start, options._target);
applyOffset(end, options._offset);
if (!arePositionsDifferent(start, end) && options._altTarget) {
end = getEndPosition(scrollable, start, options._altTarget);
applyOffset(end, options._altOffset);
}
return { _start: start, _end: end };
};
// must be called in "measure time"
const getEndPosition = (
scrollable: Element,
startPosition: ScrollPosition,
targetCoordinates: TargetCoordinates,
): ScrollPosition => {
// by default no change in scroll top or left
const endPosition = MH.copyObject(startPosition);
if (!MH.isNullish(targetCoordinates?.top)) {
if (MH.isFunction(targetCoordinates.top)) {
endPosition.top = targetCoordinates.top(scrollable);
} else {
endPosition.top = targetCoordinates.top;
}
}
if (!MH.isNullish(targetCoordinates?.left)) {
if (MH.isFunction(targetCoordinates.left)) {
endPosition.left = targetCoordinates.left(scrollable);
} else {
endPosition.left = targetCoordinates.left;
}
}
// Set boundaries
const scrollH = scrollable[MC.S_SCROLL_HEIGHT];
const scrollW = scrollable[MC.S_SCROLL_WIDTH];
const clientH = getClientHeightNow(scrollable);
const clientW = getClientWidthNow(scrollable);
endPosition.top = MH.min(scrollH - clientH, endPosition.top);
endPosition.top = MH.max(0, endPosition.top);
endPosition.left = MH.min(scrollW - clientW, endPosition.left);
endPosition.left = MH.max(0, endPosition.left);
return endPosition;
};
const initiateScroll = async (
options: ScrollToOptionsInternal,
isCancelled: () => boolean,
) => {
const position = await getStartEndPosition(options);
const duration = options._duration;
const scrollable = options._scrollable;
const existingScrollInfo = currentScrollInfos.get(scrollable);
const currentPosition = existingScrollInfo?._position ?? position._start;
const currentVelocity = existingScrollInfo?._velocity ?? {
[MC.S_TOP]: 0,
[MC.S_LEFT]: 0,
};
let elapsed = existingScrollInfo?._elapsed;
const logger = debug
? new debug.Logger({
name: `scroll-${formatAsString(scrollable)}-${randId()}`,
logAtCreation: {
options,
position,
elapsed,
currentPosition: MH.copyObject(currentPosition),
currentVelocity: MH.copyObject(currentVelocity),
},
})
: null;
for await (elapsed of newAnimationFrameIterator(elapsed)) {
const deltaTime = elapsed.sinceLast;
if (deltaTime === 0) {
// First time
continue;
}
// Element.scrollTo equates to a measurement and needs to run after
// painting to avoid forced layout.
await waitForMeasureTime();
if (isCancelled()) {
// Reject the promise
logger?.debug8("Cancelled");
throw currentPosition;
}
for (const s of [MC.S_LEFT, MC.S_TOP] as const) {
const { l, v } = criticallyDamped({
l: currentPosition[s],
v: currentVelocity[s],
lTarget: position._end[s],
dt: deltaTime,
lag: duration,
});
currentPosition[s] = l;
currentVelocity[s] = v;
}
updateCurrentScrollInfo(scrollable, {
_position: currentPosition,
_velocity: currentVelocity,
_elapsed: elapsed,
});
const isDone = !arePositionsDifferent(currentPosition, position._end, 0.5);
if (isDone) {
MH.assign(currentPosition, position._end); // use exact final coordinates
}
MH.elScrollTo(scrollable, currentPosition);
if (isDone) {
logger?.debug8("Done");
break;
}
}
return currentPosition;
};
// ------------------------------
let mainContentElement: HTMLElement;
let mainScrollableElement: HTMLElement;
let initPromise: Promise<void> | null = null;
const init = (): Promise<void> => {
if (!initPromise) {
initPromise = (async () => {
const mainScrollableElementSelector =
settings.mainScrollableElementSelector;
const contentElement = await waitForElementOrInteractive(() => {
return mainScrollableElementSelector
? MH.docQuerySelector(mainScrollableElementSelector)
: MH.getBody(); // default if no selector
});
// defaults
mainScrollableElement = getDefaultScrollingElement();
mainContentElement = MH.getBody();
if (!contentElement) {
logError(
MH.usageError(
`No match for '${mainScrollableElementSelector}'. ` +
"Scroll tracking/capturing may not work as intended.",
),
);
} else if (!MH.isHTMLElement(contentElement)) {
logWarn("mainScrollableElementSelector should point to an HTMLElement");
} else if (contentElement !== mainContentElement) {
mainScrollableElement = mainContentElement = contentElement;
}
})();
}
return initPromise;
};
// Try to find the main scrollable/content elements asap so that tryGetMain*
// can return them if called before fetchMain*
if (MH.hasDOM()) {
waitForInteractive().then(init);
}
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