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* @module Watchers/ViewWatcher
*/
import * as MC from "@lisn/globals/minification-constants";
import * as MH from "@lisn/globals/minification-helpers";
import {
ViewTarget,
View,
BoundingRect,
CommaSeparatedStr,
} from "@lisn/globals/types";
import { setNumericStyleJsVars } from "@lisn/utils/css-alter";
import { waitForInteractive } from "@lisn/utils/dom-events";
import {
waitForMeasureTime,
waitForSubsequentMeasureTime,
} from "@lisn/utils/dom-optimize";
import { logError } from "@lisn/utils/log";
import { omitKeys, compareValuesIn } from "@lisn/utils/misc";
import { createOverlay, OverlayOptions } from "@lisn/utils/overlays";
import { getClosestScrollable } from "@lisn/utils/scroll";
import { fetchViewportSize } from "@lisn/utils/size";
import { toMargins, objToStrKey } from "@lisn/utils/text";
import {
VIEWS_SPACE,
getViewsBitmask,
parseScrollOffset,
} from "@lisn/utils/views";
import {
CallbackHandler,
Callback,
wrapCallback,
} from "@lisn/modules/callback";
import { newXMap, newXWeakMap } from "@lisn/modules/x-map";
import { XIntersectionObserver } from "@lisn/modules/x-intersection-observer";
import { DOMWatcher } from "@lisn/watchers/dom-watcher";
import { ScrollWatcher } from "@lisn/watchers/scroll-watcher";
import { SizeWatcher } from "@lisn/watchers/size-watcher";
import debug from "@lisn/debug/debug";
/**
* {@link ViewWatcher} monitors the position of a given target relative to the
* given {@link ViewWatcherConfig.root | root} or the viewport.
*
* It's built on top of
* {@link https://developer.mozilla.org/en-US/docs/Web/API/IntersectionObserver | IntersectionObserver}.
*
* It manages registered callbacks globally and reuses IntersectionObservers
* for more efficient performance.
*/
export class ViewWatcher {
/**
* Call the given handler whenever the {@link ViewWatcherConfig.root | root}'s
* view relative to the target position changes, i.e. when the target enters
* or leaves the root.
*
* Unless {@link OnViewOptions.skipInitial} is true, the handler is also
* called (almost) immediately with the current view if it matches this
* set of options*.
*
* **IMPORTANT:** The same handler can _not_ be added multiple times for the
* same target, even if the options differ. If the handler has already been
* added for this target, either using {@link trackView} or using
* {@link onView}, then it will be removed and re-added with the current
* options. So if previously it was also tracking position across root
* using {@link trackView}, it will no longer do so.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the target or the options are invalid.
*/
readonly onView: (
target: ViewTarget,
handler: OnViewHandler,
options?: OnViewOptions,
) => Promise<void>;
/**
* Removes a previously added handler.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the target is invalid.
*/
readonly offView: (target: ViewTarget, handler: OnViewHandler) => void;
/**
* This does more than just {@link onView}. The difference is that in
* addition to a change of {@link View}, such as the target entering or
* leaving the ViewWatcher's {@link ViewWatcherConfig.root | root} (by
* default the viewport), the handler is also called each time the target's
* relative view changes _while inside the root_.
*
* A change of relative position happens when:
* - the target is resized
* - the root is resized
* - the any of the target's scrollable ancestors is scrolled
* - the target's attributes changed that resulted in a change of position
*
* All of the above are accounted for. Internally it uses
* {@link ScrollWatcher}, {@link DOMWatcher} and {@link SizeWatcher} to keep
* track of all of this.
*
* If the target is leaves the ViewWatcher's
* {@link ViewWatcherConfig.root | root}, the handler will be called with
* the {@link ViewData}, and the above events will stop being tracked until
* the target enters the watcher's root again.
*
* **IMPORTANT:** The same handler can _not_ be added multiple times for the
* same target, even if the options differ. If the handler has already been
* added for this target, either using {@link trackView} or using
* {@link onView}, then it will be removed and re-added with the current
* options.
*
* ------
*
* If `handler` is not given, then it defaults to an internal handler that
* updates the following set of CSS variables on the target's style and
* represent its relative position:
*
* - `--lisn-js--r-top`
* - `--lisn-js--r-bottom`
* - `--lisn-js--r-left`
* - `--lisn-js--r-right`
* - `--lisn-js--r-width`
* - `--lisn-js--r-height`
* - `--lisn-js--r-h-middle`
* - `--lisn-js--r-v-middle`
*
* See {@link ViewData.relative} for an explanation of each.
*
* Note that only Element targets are supported here and not offsets.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the target or "views" are invalid.
*/
readonly trackView: (
element: Element,
handler?: OnViewHandler | null,
options?: TrackViewOptions,
) => Promise<void>;
/**
* Removes a previously added handler for {@link trackView}.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the target is invalid.
*/
readonly noTrackView: (
element: Element,
handler?: OnViewHandler | null,
) => void;
/**
* Get the current view relative to the target. By default, it will
* {@link waitForMeasureTime} and so will be delayed by one frame.
*
* @param realtime If true, it will not {@link waitForMeasureTime}. Use
* this only when doing realtime scroll-based animations
* as it may cause a forced layout.
*/
readonly fetchCurrentView: (
target: ViewTarget,
realtime?: boolean,
) => Promise<ViewData>;
/**
* Creates a new instance of ViewWatcher with the given
* {@link ViewWatcherConfig}. It does not save it for future reuse.
*/
static create(config?: ViewWatcherConfig) {
return new ViewWatcher(getConfig(config), CONSTRUCTOR_KEY);
}
/**
* Returns an existing instance of ViewWatcher with the given
* {@link ViewWatcherConfig}, or creates a new one.
*
* **NOTE:** It saves it for future reuse, so don't use this for temporary
* short-lived watchers.
*/
static reuse(config?: ViewWatcherConfig) {
const myConfig = getConfig(config);
const configStrKey = objToStrKey(omitKeys(myConfig, { _root: null }));
let instance = instances.get(myConfig._root)?.get(configStrKey);
if (!instance) {
instance = new ViewWatcher(myConfig, CONSTRUCTOR_KEY);
instances.sGet(myConfig._root).set(configStrKey, instance);
}
return instance;
}
private constructor(
config: ViewWatcherConfigInternal,
key: typeof CONSTRUCTOR_KEY,
) {
if (key !== CONSTRUCTOR_KEY) {
throw MH.illegalConstructorError("ViewWatcher.create");
}
const logger = debug
? new debug.Logger({ name: "ViewWatcher", logAtCreation: config })
: null;
const allViewData = MH.newWeakMap<Element, ViewData>();
const allCallbacks = newXWeakMap<
Element,
Map<
OnViewHandler,
{
_callback: OnViewCallback;
_trackType: TrackType;
_options: OnViewOptionsInternal;
}
>
>(() => MH.newMap());
const intersectionHandler = (entries: IntersectionObserverEntry[]) => {
debug: logger?.debug9(`Got ${entries.length} new entries`, entries);
for (const entry of entries) {
processEntry(entry);
}
};
const observeOptions = {
root: config._root,
threshold: config._threshold,
rootMargin: config._rootMargin,
};
const xObserver = new XIntersectionObserver(
intersectionHandler,
observeOptions,
);
// ----------
const fetchCurrentView = (
element: Element,
realtime = false,
): Promise<ViewData> => {
const fetchData = async (
entryOrElement: IntersectionObserverEntry | Element,
) => {
const intersection = await fetchIntersectionData(
config,
entryOrElement,
realtime,
);
const data = await fetchViewData(intersection, realtime);
return data;
};
Iif (realtime) {
return fetchData(element);
}
return MH.newPromise((resolve) => {
// Use a temp IntersectionObserver
const observer = MH.newIntersectionObserver((entries) => {
const promise = fetchData(entries[0]);
observer.disconnect();
promise.then(resolve);
}, observeOptions);
observer.observe(element);
});
};
// ----------
const createCallback = (
handler: OnViewHandler,
options: OnViewOptionsInternal,
trackType: TrackType,
): OnViewCallback => {
const element = options._element;
MH.remove(allCallbacks.get(element)?.get(handler)?._callback);
debug: logger?.debug5("Adding/updating handler", options);
const callback = wrapCallback(handler);
callback.onRemove(() => {
deleteHandler(handler, options);
});
allCallbacks.sGet(element).set(handler, {
_callback: callback,
_trackType: trackType,
_options: options,
});
return callback;
};
// ----------
const setupOnView = async (
target: ViewTarget,
handler: OnViewHandler,
userOptions: (OnViewOptions & TrackViewOptions) | undefined,
trackType: TrackType,
) => {
const options = await fetchOptions(config._root, target, userOptions);
const element = options._element;
const callback = createCallback(handler, options, trackType);
// View watcher should be used before the DOM is loaded since the initial
// size of the root may be 0 or close to 0 and would lead to premature
// triggering.
await waitForInteractive();
// Initial call doesn't need to be realtime, and best to use an actual
// IntersectionObserverEntry for that one.
let viewData = await fetchCurrentView(element);
Iif (
viewData.rootBounds[MC.S_WIDTH] === 0 &&
viewData.rootBounds[MC.S_HEIGHT] === 0
) {
// Possibly the root is being setup now, wait for one AF
debug: logger?.debug5(
"Got zero root size, deferring for a bit",
config._root,
);
await waitForSubsequentMeasureTime();
viewData = await fetchCurrentView(element);
}
if (trackType === TRACK_FULL) {
// Detect resize or scroll
await setupInviewTrack(options, callback, viewData);
}
if (callback.isRemoved()) {
return;
}
// Always use observeLater to skip the initial call from the
// IntersectionObserver, and call callbacks that have skipInitial: false
// here. Otherwise, we can't tell from inside the intersectionHandler whether
// a callback wants to skip its initial call or not.
//
// It's ok if already observed, won't do anything.
xObserver.observeLater(element);
if (!userOptions?.skipInitial) {
debug: logger?.debug5("Calling initially with", element, viewData);
if (viewsToBitmask(viewData.views) & options._viewsBitmask) {
await invokeCallback(callback, element, viewData);
}
}
};
// ----------
const removeOnView = async (
target: ViewTarget,
handler: OnViewHandler,
trackType: TrackType,
) => {
// For time sync, so that if called immediately after onView without
// awaiting, it will remove the callback that is about to be added.
// But if no such handler has been added we may unnecessarily
// create an overlay... TODO
const options = await fetchOptions(config._root, target, {});
const element = options._element;
const currEntry = allCallbacks.get(element)?.get(handler);
if (currEntry?._trackType === trackType) {
MH.remove(currEntry._callback);
if (handler === setViewCssProps) {
// delete the properties
setViewCssProps(element, null);
}
}
};
// ----------
const deleteHandler = (
handler: OnViewHandler,
options: OnViewOptionsInternal,
) => {
const element = options._element;
MH.deleteKey(allCallbacks.get(element), handler);
allCallbacks.prune(element);
if (!allCallbacks.has(element)) {
debug: logger?.debug4(
"No more callbacks for target; unobserving",
element,
);
xObserver.unobserve(element);
MH.deleteKey(allViewData, element);
}
};
// ----------
const processEntry = async (entry: IntersectionObserverEntry) => {
// In reality, it can't be just a base Element
const element = MH.targetOf(entry);
// This doesn't need to be "realtime", since IntersectionObserver alone
// introduces a delay.
const intersection = await fetchIntersectionData(config, entry);
const latestData = await fetchViewData(intersection);
debug: logger?.debug9("Got ViewData", element, latestData);
const viewsBitmask = viewsToBitmask(latestData.views);
for (const entry of allCallbacks.get(element)?.values() || []) {
if (viewsBitmask & entry._options._viewsBitmask) {
invokeCallback(entry._callback, element, latestData);
}
}
};
// ----------
const setupInviewTrack = async (
options: OnViewOptionsInternal,
viewCallback: OnViewCallback,
viewData: ViewData,
) => {
const element = options._element;
debug: logger?.debug8(
"Setting up size, scroll and attribute tracking",
element,
);
const sizeWatcher = SizeWatcher.reuse();
const scrollWatcher = ScrollWatcher.reuse();
const realtime = options._debounceWindow === 0;
// Detect when target's class or style attribute change
const domWatcher = DOMWatcher.create({
root: element,
// only direct children
subtree: false,
});
// We need to remove the tracking callback when target leaves view and re-add
// it when it enters view. But the OnViewCallback that is associated may have
// already been added prior, by calling onView with this handler, so we can't
// always wrap around it, in order to detect when it's called with a change
// of view. So we setup another OnViewCallback tied to the tracking callback.
let isInview = false;
let removeTrackCallback: (() => void) | null = null;
// Finds any scrollable ancestors of the element and detect scroll on them.
const scrollableAncestors = await fetchScrollableAncestors(
element,
realtime,
);
if (viewCallback.isRemoved()) {
return;
}
const addTrackCallback = () => {
const trackCallback = wrapCallback(async () => {
const prevData = allViewData.get(element);
// Get the latest view data for the target
const latestData = await fetchCurrentView(element, realtime);
debug: logger?.debug9("Got ViewData", element, latestData);
const changed = viewChanged(latestData, prevData);
if (changed) {
// When comparing for changes, we round the numbers to certain number
// of decimal places, and allViewData serves as a "last threshold"
// state, so only update it if there was a significant change.
// Otherwise very quick changes in small increments would get
// rejected as "no change".
allViewData.set(element, latestData);
if (isInview && !viewCallback.isRemoved()) {
// Could have been removed during the debounce window
await invokeCallback(viewCallback, element, latestData);
}
} else {
debug: logger?.debug9("ViewData same as last");
}
});
// TODO Is there a better way to detect when it's moved?
viewCallback.onRemove(trackCallback.remove);
removeTrackCallback = trackCallback.remove;
// Detect when target's class or style attribute change
domWatcher.onMutation(trackCallback, {
categories: [MC.S_ATTRIBUTE],
[MC.S_SKIP_INITIAL]: true,
});
// Detect when target is resized
sizeWatcher.onResize(trackCallback, {
target: element,
[MC.S_DEBOUNCE_WINDOW]: options._debounceWindow,
threshold: options._resizeThreshold,
[MC.S_SKIP_INITIAL]: true,
});
// Detect when the root is resized
sizeWatcher.onResize(trackCallback, {
target: config._root ?? MH.getWindow(),
[MC.S_DEBOUNCE_WINDOW]: options._debounceWindow,
threshold: options._resizeThreshold,
[MC.S_SKIP_INITIAL]: true,
});
// Detect when the target's scrollable ancestors are scrolled (this
// will almost certainly include the main scrollable element).
for (const ancestor of scrollableAncestors) {
scrollWatcher.onScroll(trackCallback, {
scrollable: ancestor,
[MC.S_DEBOUNCE_WINDOW]: options._debounceWindow,
threshold: options._scrollThreshold,
[MC.S_SKIP_INITIAL]: true,
});
}
};
const enterOrLeaveCallback = createCallback(
(target__ignored, viewData) => {
if (viewData.views[0] === MC.S_AT) {
if (!isInview) {
isInview = true;
addTrackCallback();
}
} else Iif (removeTrackCallback) {
isInview = false;
removeTrackCallback();
removeTrackCallback = null;
}
},
MH.assign(options, {
_viewsBitmask: VIEWS_SPACE.bitmask,
}),
TRACK_REGULAR,
);
viewCallback.onRemove(enterOrLeaveCallback.remove);
allViewData.set(element, viewData); // to avoid duplicate initial call
// Setup the track and the "inView" state
if (!enterOrLeaveCallback.isRemoved()) {
invokeCallback(enterOrLeaveCallback, element, viewData);
}
};
// ----------
this.fetchCurrentView = (target, realtime = false) =>
fetchElement(config._root, target).then((element) =>
fetchCurrentView(element, realtime),
);
// ----------
this.trackView = (element, handler?, options?) => {
if (!handler) {
handler = setViewCssProps;
}
return setupOnView(element, handler, options, TRACK_FULL);
};
// ----------
this.noTrackView = (element, handler?) => {
if (!handler) {
handler = setViewCssProps;
}
removeOnView(element, handler, TRACK_FULL); // no need to await
};
// ----------
this.onView = (target, handler, options?) =>
setupOnView(target, handler, options, TRACK_REGULAR);
// ----------
this.offView = (target, handler) =>
removeOnView(target, handler, TRACK_REGULAR); // no need to await
}
}
/**
* @interface
*/
export type ViewWatcherConfig = {
/**
* The root element to use for the IntersectionObserver.
*
* **NOTE:** If the target you want to observe (via
* {@link ViewWatcher.onView}) is inside a scrolling element, then you should
* probably set the watcher's root to be that scrolling element or a wrapper
* around it. However, even if you don't or can't do that, the watcher will
* try to be smart about that, and when the target is no longer intercepting
* because it's scrolled outside its scrolling container, and yet its
* bounding box is still inside the watcher root (e.g. the viewport) the
* watcher will determine the relative view based on the scrolling container
* and not the actual watcher root.
*
* @defaultValue null
*/
root?: Element | null;
/**
* The rootMargin to pass to the IntersectionObserver constructor options.
*
* @defaultValue "0px 0px 0px 0px"
*/
rootMargin?: string;
/**
* The threshold to pass to the IntersectionObserver constructor options.
*
* @defaultValue 0
*/
threshold?: number | number[];
};
/**
* @interface
*/
export type OnViewOptions = {
/**
* Specifies a list of {@link View}s to target for.
*
* The handler will only be called if there is a change of view relative to
* the target that matches the given ones.
*
* It can be a comma-separated list of "views" or an array of such names.
*
* @defaultValue undefined
*/
views?: CommaSeparatedStr<View> | View[];
/**
* Do not call the handler until there's a future resize of the element.
*
* By default we call the handler (almost) immediately with the current size
* data for the target.
*
* @defaultValue false
*/
skipInitial?: boolean;
};
/**
* @interface
*/
export type TrackViewOptions = {
/**
* Use this debounce window for the {@link ScrollWatcher} and
* {@link SizeWatcher} involved in the view tracking.
*
* **IMPORTANT:**
* If the debounce window is non-0 (default), then the callback is always
* delayed by at least an animation frame following a scroll event to allow
* for optimized `scrollTop`/`scrollLeft` measurements via
* {@link waitForMeasureTime}.
*
* If you set this is 0, this indicates that the callback should be
* "realtime" and will therefore skip {@link waitForMeasureTime}, which could
* lead to forced re-layouts during scroll, but you probably need this when
* doing scroll-based animations.
*
* @defaultValue undefined // ScrollWatcher and SizeWatcher defaults
*/
debounceWindow?: number;
/**
* Use this resize threshold for the {@link SizeWatcher} involved in the view
* tracking.
*
* @defaultValue undefined // SizeWatcher default
*/
resizeThreshold?: number;
/**
* Use this scroll threshold for the {@link ScrollWatcher} involved in the
* view tracking.
*
* @defaultValue undefined // ScrollWatcher default
*/
scrollThreshold?: number;
/**
* Do not call the handler until there's a future resize of the element.
*
* By default we call the handler (almost) immediately with the current size
* data for the target.
*
* @defaultValue false
*/
skipInitial?: boolean;
};
/**
* The handler is invoked with two arguments:
*
* - The element that is the target of the IntersectionObserver. If the call to
* {@link ViewWatcher.onView} specified an element as the target, it will be
* the same. If it specified an offset, then the element passed to the
* callback will be an absolutely positioned trigger overlay that's created
* as a result.
* - the {@link ViewData} for relative to the target
*/
export type OnViewHandlerArgs = [Element, ViewData];
export type OnViewCallback = Callback<OnViewHandlerArgs>;
export type OnViewHandler = CallbackHandler<OnViewHandlerArgs> | OnViewCallback;
export type ViewData = {
isIntersecting: boolean;
targetBounds: BoundingRect;
rootBounds: BoundingRect;
/**
* The current view or views of the target. There would be two views given
* only if the target is _not_ in view and it's diagonally across from the
* root, e.g. both below and to the right.
*/
views: [View, View?];
/**
* This is the target's position relative to the
* {@link ViewWatcherConfig.root | root} with values relative to the root
* size.
*
* It is like the {@link targetBounds} except that each quantity is scaled by
* the root's width or height, and having two additional computed values.
*/
relative: {
x: number;
y: number;
top: number;
bottom: number;
left: number;
right: number;
width: number;
height: number;
/**
* Average of the relative left and right.
*/
hMiddle: number;
/**
* Average of the relative top and bottom.
*/
vMiddle: number;
};
};
// ----------------------------------------
type ViewWatcherConfigInternal = {
_root: Element | null;
_rootMargin: string;
_threshold: number | number[];
};
type OnViewOptionsInternal = {
_element: Element;
_viewsBitmask: number;
_debounceWindow: number | undefined;
_resizeThreshold: number | undefined;
_scrollThreshold: number | undefined;
};
type IntersectionData = {
_target: Element;
_targetBounds: BoundingRect;
_root: Element | null;
_rootMargins: [number, number, number, number];
_rootBounds: BoundingRect;
_isIntersecting: boolean | null; // null means unknown, no IntersectionObserverEntry
_isCrossOrigin: boolean | null; // null means unknown, no IntersectionObserverEntry
};
type TrackType = typeof TRACK_REGULAR | typeof TRACK_FULL;
const CONSTRUCTOR_KEY: unique symbol = MC.SYMBOL() as typeof CONSTRUCTOR_KEY;
const instances = newXMap<Element | null, Map<string, ViewWatcher>>(() =>
MH.newMap(),
);
const getConfig = (
config: ViewWatcherConfig | undefined,
): ViewWatcherConfigInternal => {
return {
_root: config?.root ?? null,
_rootMargin: config?.rootMargin ?? "0px 0px 0px 0px",
_threshold: config?.threshold ?? 0,
};
};
const TRACK_REGULAR = 1; // only entering/leaving root
const TRACK_FULL = 2; // entering/leaving + moving across (fine-grained)
// --------------------
const fetchOptions = async (
root: Element | null,
target: ViewTarget,
options: (OnViewOptions & TrackViewOptions) | undefined,
): Promise<OnViewOptionsInternal> => {
return {
_element: await fetchElement(root, target),
_viewsBitmask: getViewsBitmask(options?.views),
_debounceWindow: options?.debounceWindow,
_resizeThreshold: options?.resizeThreshold,
_scrollThreshold: options?.scrollThreshold,
};
};
const fetchScrollableAncestors = async (
element: Element,
realtime: boolean,
) => {
if (!realtime) {
await waitForMeasureTime();
}
const scrollableAncestors = [];
let ancestor: Element | null | undefined = element;
while ((ancestor = getClosestScrollable(ancestor, { active: true }))) {
scrollableAncestors.push(ancestor);
}
return scrollableAncestors;
};
const viewChanged = (latestData: ViewData, prevData: ViewData | undefined) =>
!prevData ||
viewsToBitmask(prevData.views) !== viewsToBitmask(latestData.views) ||
!compareValuesIn(
MH.copyBoundingRectProps(prevData.targetBounds),
MH.copyBoundingRectProps(latestData.targetBounds),
) ||
!compareValuesIn(prevData.rootBounds, latestData.rootBounds) ||
!compareValuesIn(prevData.relative, latestData.relative);
const viewsToBitmask = (views: [View, View?]) =>
VIEWS_SPACE.bit[views[0]] | (views[1] ? VIEWS_SPACE.bit[views[1]] : 0);
const fetchIntersectionData = async (
config: ViewWatcherConfigInternal,
entryOrTarget: IntersectionObserverEntry | Element,
realtime = false,
): Promise<IntersectionData> => {
const root = config._root;
const vpSize = await fetchViewportSize(realtime);
const rootMargins = toMargins(config._rootMargin, vpSize);
let target: Element;
let targetBounds: BoundingRect;
let rootBounds: BoundingRect | null = null;
let isIntersecting: boolean | null = null;
let isCrossOrigin: boolean | null = null;
if (MH.isInstanceOf(entryOrTarget, IntersectionObserverEntry)) {
target = entryOrTarget.target;
targetBounds = entryOrTarget.boundingClientRect;
rootBounds = entryOrTarget.rootBounds;
isIntersecting = entryOrTarget.isIntersecting;
isCrossOrigin = !entryOrTarget.rootBounds;
} else E{
target = entryOrTarget;
targetBounds = await fetchBounds(target, realtime);
}
Iif (!rootBounds) {
rootBounds = await fetchBounds(root, realtime, rootMargins);
}
return {
_target: target,
_targetBounds: targetBounds,
_root: root,
_rootMargins: rootMargins,
_rootBounds: rootBounds,
_isIntersecting: isIntersecting,
_isCrossOrigin: isCrossOrigin,
};
};
const fetchBounds = async (
root: Element | null,
realtime: boolean,
rootMargins?: [number, number, number, number],
): Promise<BoundingRect> => {
let rect: BoundingRect;
if (root) {
Iif (!realtime) {
await waitForMeasureTime();
}
rect = MH.copyBoundingRectProps(MH.getBoundingClientRect(root));
} else {
const { width, height } = await fetchViewportSize(realtime);
rect = {
x: 0,
left: 0,
right: width,
width,
y: 0,
top: 0,
bottom: height,
height,
};
}
Iif (rootMargins) {
rect.x = rect[MC.S_LEFT] -= rootMargins[3];
rect[MC.S_RIGHT] += rootMargins[1];
rect[MC.S_WIDTH] += rootMargins[1] + rootMargins[3];
rect.y = rect[MC.S_TOP] -= rootMargins[0];
rect[MC.S_BOTTOM] += rootMargins[2];
rect[MC.S_HEIGHT] += rootMargins[0] + rootMargins[2];
}
return rect;
};
const fetchViewData = async (
intersection: IntersectionData,
realtime = false,
): Promise<ViewData> => {
const vpSize = await fetchViewportSize(realtime);
const vpHeight = vpSize[MC.S_HEIGHT];
const vpWidth = vpSize[MC.S_WIDTH];
const views = await fetchViews(intersection, realtime);
const relative = MH.merge(
{ hMiddle: NaN, vMiddle: NaN },
MH.copyBoundingRectProps(intersection._targetBounds),
);
relative.y /= vpHeight;
relative[MC.S_TOP] /= vpHeight;
relative[MC.S_BOTTOM] /= vpHeight;
relative[MC.S_HEIGHT] /= vpHeight;
relative.x /= vpWidth;
relative[MC.S_LEFT] /= vpWidth;
relative[MC.S_RIGHT] /= vpWidth;
relative[MC.S_WIDTH] /= vpWidth;
relative.hMiddle = (relative[MC.S_LEFT] + relative[MC.S_RIGHT]) / 2;
relative.vMiddle = (relative[MC.S_TOP] + relative[MC.S_BOTTOM]) / 2;
const viewData: ViewData = {
isIntersecting: intersection._isIntersecting ?? views[0] === MC.S_AT,
targetBounds: intersection._targetBounds,
rootBounds: intersection._rootBounds,
views,
relative,
};
return viewData;
};
const fetchViews = async (
intersection: IntersectionData,
realtime: boolean,
useScrollingAncestor?: Element,
): Promise<[View, View?]> => {
if (intersection._isIntersecting) {
return [MC.S_AT];
}
let rootBounds: BoundingRect;
Iif (useScrollingAncestor) {
rootBounds = await fetchBounds(
useScrollingAncestor,
realtime,
intersection._rootMargins,
);
} else {
rootBounds = intersection._rootBounds;
}
const targetBounds = intersection._targetBounds;
const delta = {
_left: rootBounds[MC.S_LEFT] - targetBounds[MC.S_LEFT],
_right: targetBounds[MC.S_RIGHT] - rootBounds[MC.S_RIGHT],
_top: rootBounds[MC.S_TOP] - targetBounds[MC.S_TOP],
_bottom: targetBounds[MC.S_BOTTOM] - rootBounds[MC.S_BOTTOM],
};
let xView: View | null = null;
let yView: View | null = null;
Iif (delta._left > 0 && delta._right > 0) {
// Target is wider than root: use greater delta to determine position.
// Remember, the view is the _root_ position relative to target.
xView = delta._left > delta._right ? MC.S_RIGHT : MC.S_LEFT;
} else if (delta._left > 0) {
// Target is to the left of the root
xView = MC.S_RIGHT;
} else if (delta._right > 0) {
// Target is to the right of the root
xView = MC.S_LEFT;
} // else target is horizontally contained in root, see below
Iif (delta._top > 0 && delta._bottom > 0) {
// Target is taller than root: use greater delta to determine position.
// Remember, the view is the _root_ position relative to target.
yView = delta._top > delta._bottom ? MC.S_BELOW : MC.S_ABOVE;
} else if (delta._top > 0) {
// Target is above the root
yView = MC.S_BELOW;
} else if (delta._bottom > 0) {
// Target is below the root
yView = MC.S_ABOVE;
} // else target is vertically contained in root, see below
Iif (xView && yView) {
// diagonally out of vide
return [xView, yView];
} else if (xView) {
// horizontally out of vide
return [xView];
} else if (yView) {
// vertically out of vide
return [yView];
}
// The target is contained in the root bounds and yet isIntersecting was
// not true. This means that either:
//
// 1. It may be intersecting, but we didn't get an actual
// IntersectionObserverEntry and we don't know if it's intersecting
// or not
// 2. The target is inside a scrolling element that is _not_ being used as
// the observer root, and the target has scrolled out of the scrollable
// bounds but still inside the viewport
// 3. We're inside a cross-origin iFrame and the iFrame is partially or
// fully not-intersecting
Iif (!intersection._isCrossOrigin) {
// This is case 1. or 2. => get the views relative to the closest
// scrollable ancestor relative to which it is _not_ intersecting, if
// any. If it's nested inside several scrolling elements, we'll end up
// looping over each one until we find the one for which the target is
// outside its box.
//
// It is too risky to use active isScrollable check here since we could be
// inside an onScroll handler, so just use passive.
const scrollingAncestor = getClosestScrollable(
useScrollingAncestor ?? intersection._target,
);
Iif (scrollingAncestor) {
return fetchViews(intersection, realtime, scrollingAncestor);
}
}
// Either case 3. (cross-origin iframe outside the viewport) or case 1. and
// the target is actually intersecting the root. Either way, it's to be
// considered in-view of its root.
return [MC.S_AT];
};
const setViewCssProps = (
element: Element,
viewData: ViewData | undefined | null,
) => {
const relative: Record<string, number> = viewData?.relative ?? {};
const props = {
top: relative.top,
bottom: relative.bottom,
left: relative.left,
right: relative.right,
[MC.S_WIDTH]: relative[MC.S_WIDTH],
[MC.S_HEIGHT]: relative[MC.S_HEIGHT],
hMiddle: relative.hMiddle,
vMiddle: relative.vMiddle,
};
setNumericStyleJsVars(element, props, { _prefix: "r-", _numDecimal: 4 }); // don't await here
};
const fetchElement = async (
root: Element | null,
target: ViewTarget,
): Promise<Element> => {
if (MH.isElement(target)) {
return target;
} else Iif (!MH.isString(target)) {
throw MH.usageError(
"'target' must be an offset string or an HTMLElement | SVGElement | MathMLElement",
);
}
const overlayOptions = getOverlayOptions(root, target);
return await createOverlay(overlayOptions);
};
const getOverlayOptions = (
root: Element | null,
target: string,
): OverlayOptions => {
const { reference, value } = parseScrollOffset(target);
let ovrDimension: "width" | "height";
if (reference === MC.S_TOP || reference === MC.S_BOTTOM) {
ovrDimension = MC.S_WIDTH;
} else if (reference === MC.S_LEFT || reference === MC.S_RIGHT) {
ovrDimension = MC.S_HEIGHT;
} else E{
throw MH.usageError(`Invalid offset reference: '${reference}'`);
}
return {
parent: MH.isHTMLElement(root) ? root : undefined,
style: {
[reference]: value,
[ovrDimension]: "100%",
},
};
};
const invokeCallback = (
callback: OnViewCallback,
element: Element,
viewData: ViewData,
) => callback.invoke(element, MH.copyObject(viewData)).catch(logError);
|