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* @module Widgets
*/
import * as MC from "@lisn/globals/minification-constants";
import * as MH from "@lisn/globals/minification-helpers";
import { ScrollOffsetSpec } from "@lisn/globals/types";
import {
showElement,
hideElement,
displayElement,
displayElementNow,
undisplayElement,
disableInitialTransition,
addClassesNow,
removeClassesNow,
setDataNow,
setBooleanDataNow,
delDataNow,
getParentFlexDirection,
} from "@lisn/utils/css-alter";
import {
replaceElementNow,
wrapElementNow,
moveElement,
moveElementNow,
insertArrow,
} from "@lisn/utils/dom-alter";
import { waitForElement } from "@lisn/utils/dom-events";
import { waitForMutateTime } from "@lisn/utils/dom-optimize";
import { waitForReferenceElement } from "@lisn/utils/dom-search";
import { addEventListenerTo, removeEventListenerFrom } from "@lisn/utils/event";
import { validateString } from "@lisn/utils/validation";
import { isValidScrollOffset } from "@lisn/utils/views";
import { ScrollWatcher } from "@lisn/watchers/scroll-watcher";
import { ViewWatcher } from "@lisn/watchers/view-watcher";
import {
Widget,
WidgetConfigValidatorFunc,
registerWidget,
} from "@lisn/widgets/widget";
/**
* Configures the given element as a {@link ScrollToTop} widget.
*
* The ScrollToTop widget adds a scroll-to-top button in the lower right corder
* of the screen (can be changed to bottom left) which scrolls smoothly (and
* more slowly than the native scroll) back to the top.
*
* The button is only shown when the scroll offset from the top is more than a
* given configurable amount.
*
* **IMPORTANT:** When configuring an existing element as the button (i.e. using
* `new ScrollToTop` or auto-widgets, rather than {@link ScrollToTop.enableMain}):
* - if using
* {@link Settings.settings.mainScrollableElementSelector | the main scrolling element}
* as the scrollable, the button element will have it's CSS position set to `fixed`;
* - otherwise, if using a custom scrollable element, the button element may be
* moved in the DOM tree in order to position it on top of the scrollable
* If you don't want the button element changed in any way, then consider using
* the {@link Triggers.ClickTrigger | ClickTrigger} with a
* {@link Actions.ScrollTo | ScrollTo} action.
*
* **IMPORTANT:** You should not instantiate more than one {@link ScrollToTop}
* widget on a given element. Use {@link ScrollToTop.get} to get an existing
* instance if any. If there is already a widget instance, it will be destroyed!
*
* -----
*
* You can use the following dynamic attributes or CSS properties in your
* stylesheet:
*
* The following dynamic attributes are set on the element:
* - `data-lisn-place`: `"left"` or `"right"`
*
* -----
*
* To use with auto-widgets (HTML API) (see
* {@link Settings.settings.autoWidgets | settings.autoWidgets}), the following
* CSS classes or data attributes are recognized:
* - `lisn-scroll-to-top` class or `data-lisn-scroll-to-top` attribute set on
* the element that constitutes the widget. The element should be empty.
*
* See below examples for what values you can use set for the data attributes
* in order to modify the configuration of the automatically created widget.
*
* @example
* This will create a scroll-to-top button using the JavaScript API.
*
* This will work even if
* {@link Settings.settings.autoWidgets | settings.autoWidgets}) is false.
*
* ```html
* <!-- LISN should be loaded beforehand -->
* <script>
* LISN.widgets.ScrollToTop.enableMain({
* position: "left",
* offset: "top: 300vh"
* });
* </script>
* ```
*
* You can customise the offset show/hide trigger via CSS as well as long as
* {@link ScrollToTopConfig.offset} is left at its default value which uses
* this CSS property:
*
* ```html
* <style type="text/css" media="screen">
* :root {
* --lisn-scroll-to-top--offset: 300vh;
* }
* </style>
* ```
*
* @example
* This will configure the given element as a scroll-to-top button for the main
* scrolling element using an existing element for the button with default
* {@link ScrollToTopConfig}.
*
* ```html
* <button class="lisn-scroll-to-top"></button>
* ```
* @example
* As above but with custom settings.
*
* ```html
* <button data-lisn-scroll-to-top="position=left | offset=top:300vh"></button>
* ```
*
* @example
* This will configure the given element as a scroll-to-top button for a custom
* scrolling element (i.e. one with overflow "auto" or "scroll").
*
* ```html
* <div id="scrollable">
* <!-- content here... -->
* </div>
* <button data-lisn-scroll-to-top="scrollable=#scrollable"></button>
* ```
*
* @example
* As above, but using a reference specification with a class name to find the
* scrollable.
*
* ```html
* <div class="scrollable">
* <!-- content here... -->
* </div>
* <button data-lisn-scroll-to-top="scrollable=prev.scrollable"></button>
* ```
*
* @example
* As above but with all custom settings.
*
* ```html
* <div class="scrollable">
* <!-- content here... -->
* </div>
* <button data-lisn-scroll-to-top="scrollable=prev.scrollable
* | position=left
* | offset=top:300vh
* "></button>
* ```
*/
export class ScrollToTop extends Widget {
/**
* If element is omitted, returns the instance created by {@link enableMain}
* if any.
*/
static get(element?: Element): ScrollToTop | null {
if (!element) {
return mainWidget;
}
const instance = super.get(element, DUMMY_ID);
if (MH.isInstanceOf(instance, ScrollToTop)) {
return instance;
}
return null;
}
static register() {
registerWidget(
WIDGET_NAME,
(element, config) => {
if (!ScrollToTop.get(element)) {
return new ScrollToTop(element, config);
}
return null;
},
newConfigValidator,
);
}
/**
* Creates a new button element, inserts it into the document body and
* configures it as a {@link ScrollToTop}.
*/
static enableMain(config?: ScrollToTopConfig) {
const button = MH.createButton("Back to top");
const widget = new ScrollToTop(button, config);
widget.onDestroy(() => {
Iif (mainWidget === widget) {
mainWidget = null;
}
return moveElement(button);
});
waitForElement(MH.getBody).then((body) => {
if (!widget.isDestroyed()) {
moveElement(button, { to: body });
}
});
mainWidget = widget;
return widget;
}
constructor(element: Element, config?: ScrollToTopConfig) {
const destroyPromise = ScrollToTop.get(element)?.destroy();
super(element, { id: DUMMY_ID });
const offset: ScrollOffsetSpec =
config?.offset ||
`${MC.S_TOP}: var(${MH.prefixCssVar("scroll-to-top--offset")}, 200vh)`;
const position: "left" | "right" = config?.position || MC.S_RIGHT;
const scrollable = config?.scrollable;
const hasCustomScrollable =
scrollable &&
scrollable !== MH.getDocElement() &&
scrollable !== MH.getBody();
const scrollWatcher = ScrollWatcher.reuse();
const viewWatcher = ViewWatcher.reuse(
hasCustomScrollable ? { root: scrollable } : {},
);
const clickListener = () =>
scrollWatcher.scrollTo({ top: 0, left: 0 }, { scrollable });
let arrow: Element;
let placeholder: Element;
let root = element;
const showIt = () => {
showElement(root);
};
const hideIt = () => {
hideElement(root);
};
// SETUP ------------------------------
(destroyPromise || MH.promiseResolve()).then(async () => {
const flexDirection = scrollable
? await getParentFlexDirection(scrollable)
: null;
await waitForMutateTime();
if (this.isDestroyed()) {
return;
}
if (hasCustomScrollable) {
// Add a placeholder to restore its position on destroy.
placeholder = MH.createElement("div");
moveElementNow(placeholder, {
to: element,
position: "before",
ignoreMove: true,
});
// Then move it to immediately after the scrollable.
// If the parent is a horizontal flexbox and position is left, then
// we need to insert it before the scrollable.
const shouldInsertBefore =
flexDirection === "column-reverse" ||
(position === MC.S_LEFT && flexDirection === "row") ||
(position === MC.S_RIGHT && flexDirection === "row-reverse");
moveElementNow(element, {
to: scrollable,
position: shouldInsertBefore ? "before" : "after",
ignoreMove: true,
});
// Wrap the button.
root = wrapElementNow(element, { wrapper: "div", ignoreMove: true });
}
disableInitialTransition(root);
addClassesNow(root, PREFIX_ROOT);
addClassesNow(element, PREFIX_BTN);
setBooleanDataNow(root, PREFIX_FIXED, !hasCustomScrollable);
setDataNow(root, MC.PREFIX_PLACE, position);
arrow = insertArrow(element, MC.S_UP);
hideIt(); // initial
addEventListenerTo(element, MC.S_CLICK, clickListener);
viewWatcher.onView(offset, showIt, {
views: [MC.S_AT, MC.S_BELOW],
});
viewWatcher.onView(offset, hideIt, {
views: [MC.S_ABOVE],
});
this.onDisable(() => {
undisplayElement(root);
});
this.onEnable(() => {
displayElement(root);
});
this.onDestroy(async () => {
await waitForMutateTime();
removeEventListenerFrom(element, MC.S_CLICK, clickListener);
removeClassesNow(root, PREFIX_ROOT);
removeClassesNow(element, PREFIX_BTN);
delDataNow(root, PREFIX_FIXED);
delDataNow(root, MC.PREFIX_PLACE);
displayElementNow(root); // revert undisplay by onDisable
if (arrow) {
moveElementNow(arrow); // remove
}
if (root !== element) {
// Unwrap the button.
replaceElementNow(root, element, { ignoreMove: true });
}
if (placeholder) {
// Move it back into its original position.
replaceElementNow(placeholder, element, { ignoreMove: true });
}
viewWatcher.offView(offset, showIt);
viewWatcher.offView(offset, hideIt);
});
});
}
}
/**
* @interface
*/
export type ScrollToTopConfig = {
/**
* The button will be shown when the scroll top offset of the page is below
* the given value, and hidden otherwise. Accepts a colon-separated key:value
* string where the key is "top" or "bottom" (or if your page scrolls
* horizontally, then use "left" or "right"), and the value can be any valid
* CSS length specification, e.g. "top: 200vh" or "top: var(--offset, 50%)".
*
* Alternatively, you set the `--lisn-scroll-to-top--offset` CSS variable on
* the document root, which is used by the default value.
*
* @defaultValue "top: var(--lisn-scroll-to-top--offset, 200vh)"
*/
offset?: ScrollOffsetSpec;
/**
* The horizontal position of the scroll-to-top button.
*
* @defaultValue "right"
*/
position?: "left" | "right";
/**
* The element that should be scrolled.
*
* @defaultValue {@link ScrollWatcher} default
*/
scrollable?: Element;
};
// --------------------
const WIDGET_NAME = "scroll-to-top";
const PREFIXED_NAME = MH.prefixName(WIDGET_NAME);
// Only one ScrollToTop widget per element is allowed, but Widget requires a
// non-blank ID.
const DUMMY_ID = PREFIXED_NAME;
const PREFIX_ROOT = `${PREFIXED_NAME}__root`;
const PREFIX_BTN = `${PREFIXED_NAME}__btn`;
const PREFIX_FIXED = MH.prefixName("fixed");
let mainWidget: ScrollToTop | null = null;
// For HTML API only
const newConfigValidator: WidgetConfigValidatorFunc<ScrollToTopConfig> = (
element,
) => {
return {
offset: (key, value) => validateString(key, value, isValidScrollOffset),
position: (key, value) =>
validateString(key, value, (v) => v === MC.S_LEFT || v === MC.S_RIGHT),
scrollable: (key, value) =>
MH.isLiteralString(value)
? waitForReferenceElement(value, element).then((v) => v ?? undefined) // ugh, typescript...
: undefined,
};
};
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