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* @module Triggers
*
* @categoryDescription Scroll
* {@link ScrollTrigger} allows you to run actions when the user scrolls a
* target element (or the main scrollable element) in a given direction, and
* undo those actions when they scroll in the opposite direction.
*/
import * as MC from "@lisn/globals/minification-constants";
import * as MH from "@lisn/globals/minification-helpers";
import {
XYDirection,
CommaSeparatedStr,
ScrollTarget,
} from "@lisn/globals/types";
import {
getOppositeXYDirections,
isValidXYDirection,
} from "@lisn/utils/directions";
import { waitForReferenceElement } from "@lisn/utils/dom-search";
import { validateStrList, validateNumber } from "@lisn/utils/validation";
import { Action } from "@lisn/actions/action";
import { ScrollWatcher } from "@lisn/watchers/scroll-watcher";
import {
registerTrigger,
Trigger,
TriggerConfig,
} from "@lisn/triggers/trigger";
import { WidgetConfigValidatorFunc } from "@lisn/widgets/widget";
/**
* {@link ScrollTrigger} allows you to run actions when the user scrolls a
* target element (or the main scrollable element) in a given direction, and
* undo those actions when they scroll in the opposite direction.
*
* -------
*
* To use with auto-widgets (HTML API), see {@link registerTrigger} for the
* specification.
*
* - Arguments (optional): One or more (comma-separated)
* {@link ScrollTriggerConfig.directions | scroll directions}.
* Note that if you do not specify any directions, then the trigger will just
* run once, on the first scroll in any direction.
*
* - Additional trigger options (see {@link ScrollTriggerConfig}):
* - `scrollable`: A string element specification.
* See {@link Utils.getReferenceElement | getReferenceElement}.
* - `threshold`: A number.
*
* @example
* Show the element when the user scrolls the page up, hide when scrolling
* down. User scrolling left or right not trigger the action. See
* {@link getOppositeXYDirections}:
*
* ```html
* <div data-lisn-on-scroll="up @show"></div>
* ```
*
* @example
* As above, but using a CSS class instead of data attribute:
*
* ```html
* <div class="lisn-on-scroll--up@show"></div>
* ```
*
* @example
* Show the element 1000ms after the first time the user scrolls the page up:
*
* ```html
* <div data-lisn-on-scroll="up @show +once +delay=1000"></div>
* ```
*
* @example
* Add class `scrolled` the first time the user scrolls the page in any
* direction (note that the `once` option is implied here), and show the
* element 1000ms after each time the user scrolls the page up, hide it as soon
* as they scroll down:
*
* ```html
* <div data-lisn-on-scroll="@add-class: scrolled ;
* up @show +do-delay=1000"
* ></div>
* ```
*
* @example
* When the user scrolls up or down the closest ancestor with class `section`,
* then add classes `c1` and `c2` and enable trigger `my-trigger` defined on
* this same element; undo all of that when scrolling right or left:
*
* ```html
* <div class="section">
* <div data-lisn-on-scroll="up,down @add-class: c1,c2 @enable: my-trigger +scrollable=this.section"
* data-lisn-on-run="@show +id=my-trigger"
* ></div>
*</div>
* ```
*
* @example
* As above, but using `data-lisn-ref` attribute instead of class selector.
*
* ```html
* <div data-lisn-ref="section">
* <div data-lisn-on-scroll="up,down @add-class: c1,c2 @enable: my-trigger +scrollable=this-section"
* data-lisn-on-run="@show +id=my-trigger"
* ></div>
*</div>
* ```
*
* @category Scroll
*/
export class ScrollTrigger extends Trigger {
readonly getConfig: () => ScrollTriggerConfig;
static register() {
registerTrigger(
MC.S_SCROLL,
(element, args, actions, config) => {
return new ScrollTrigger(
element,
actions,
MH.assign(config, {
directions: validateStrList("directions", args, isValidXYDirection),
}),
);
},
newConfigValidator,
);
}
/**
* If no actions are supplied, nothing is done.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the config is invalid.
*/
constructor(
element: Element,
actions: Action[],
config?: ScrollTriggerConfig,
) {
config ??= {};
let directions = config.directions;
Iif (!directions) {
config.once = true;
directions = [MC.S_UP, MC.S_DOWN, MC.S_LEFT, MC.S_RIGHT];
}
super(element, actions, config);
this.getConfig = () => MH.copyObject(config);
Iif (!MH.lengthOf(actions)) {
return;
}
const watcher = ScrollWatcher.reuse();
const scrollable = config.scrollable;
const threshold = config.threshold;
const oppositeDirections = directions
? getOppositeXYDirections(directions)
: [];
watcher.onScroll(this.run, {
directions,
scrollable,
threshold,
});
if (MH.lengthOf(oppositeDirections)) {
watcher.onScroll(this.reverse, {
directions: oppositeDirections,
scrollable,
threshold,
});
}
}
}
/**
* @category Scroll
* @interface
*/
export type ScrollTriggerConfig = TriggerConfig & {
/**
* The {@link XYDirection}s to use as the trigger.
* See also {@link Watchers/ScrollWatcher.OnScrollOptions | OnScrollOptions}
*
* Actions will be "done" when the scroll direction is one of the given ones
* and "undone" when it's the opposite direction. E.g. for "up" the opposite
* is "down".
*/
directions?: CommaSeparatedStr<XYDirection> | XYDirection[];
/**
* The scrolling element target to use for the ScrollWatcher.
* See {@link Watchers/ScrollWatcher.OnScrollOptions | OnScrollOptions}
*
* @defaultValue {@link ScrollWatcher} default, the main scrolling element
*/
scrollable?: ScrollTarget;
/**
* The scroll threshold to pass to the {@link ScrollWatcher}.
* See also {@link Watchers/ScrollWatcher.OnScrollOptions | OnScrollOptions}
*
* @defaultValue {@link ScrollWatcher} default
*/
threshold?: number;
};
// --------------------
const newConfigValidator: WidgetConfigValidatorFunc<
Omit<ScrollTriggerConfig, "directions">
> = (element) => {
return {
scrollable: (key, value) =>
MH.isLiteralString(value)
? waitForReferenceElement(value, element).then((v) => v ?? undefined) // ugh, typescript...
: undefined,
threshold: validateNumber,
};
};
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