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* @module Watchers/LayoutWatcher
*/
// NOTES FOR DEVELOPERS
//
// For each layout (device or aspect ratio), we create an overlay that has a
// a width that corresponds to the layout:
// - for device layouts, it's a fixed width in pixels, equal to the minimum
// width of the device
// - for aspect ratio layouts, the overlay has a width that's relative to
// the root's height, equal to the minimum width of the aspect ratio
//
// Then we observe each overlay with an IntersectionObserver whose root
// is this Watcher's root and whose root margin is -100% from the left (i.e.
// right-most edge of the root).
//
// If the root is null, i.e. the viewport, the overlays will have a "fixed"
// position and be inserted in document.body. Otherwise, they'll be inserted
// in the root element with an "absolute" position. The root element, if not
// body must be positioned. Overlays ensures it gets a default position of
// "relative".
//
// If using custom root we track its size through SizeWatcher as the
// aspectRatio overlays are relative to the height, and we can't rely on CSS
// alone as the root may not have a fixed height through CSS.
//
// Whenever any overlay intersects the root, this means that the viewport
// width is now equal to or narrower than the overlay.
//
// ~~~~ The current device or aspect ratio corresponds to the _widest_
// ~~~~ overlay that does not intersect.
//
// For example:
//
// | mobile
// ========| mobile-wide
// ======================| tablet
// =========================================| desktop
//
// _________________________________| viewport width
//
// Here, mobile, mobile-wide and tablet overlays are _not_ intersecting, only
// desktop intersects. The device layout is therefore tablet.
//
// Therefore:
// - have the layout bit spaces ordered from narrowest layout at lowest bit
// to widest layout at hightest bit
// - keep a running bitmask of which overlays are not intersecting and update
// it each time there is an IntersectionObserverEntry.
// - get the highest device or aspect ratio bit in that bitmask to find out
// the widest non-intersecting overlay
//
// For simplicity we create overlays also for layouts that have a 0-width.
import * as MC from "@lisn/globals/minification-constants";
import * as MH from "@lisn/globals/minification-helpers";
import { settings } from "@lisn/globals/settings";
import {
Layout,
DeviceSpec,
Device,
AspectRatioSpec,
AspectRatio,
} from "@lisn/globals/types";
import { getData } from "@lisn/utils/css-alter";
import {
getLayoutBitmask,
NUM_LAYOUTS,
ORDERED_DEVICES,
ORDERED_ASPECTR,
} from "@lisn/utils/layout";
import { logError, logWarn } from "@lisn/utils/log";
import { omitKeys, copyExistingKeys } from "@lisn/utils/misc";
import { createOverlay } from "@lisn/utils/overlays";
import { objToStrKey } from "@lisn/utils/text";
import {
CallbackHandler,
Callback,
wrapCallback,
} from "@lisn/modules/callback";
import { newXMap } from "@lisn/modules/x-map";
import { SizeWatcher } from "@lisn/watchers/size-watcher";
import debug from "@lisn/debug/debug";
/**
* {@link LayoutWatcher} listens for changes in either the width or aspect
* ratio of the viewport or the given {@link LayoutWatcherConfig.root | root}.
*
* It does not track resize events; rather 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 LayoutWatcher {
/**
* Call the given handler whenever the layout changes.
*
* Unless {@link OnLayoutOptions.skipInitial} is true, the handler is also
* called (almost) immediately with the current layout.
*
* **IMPORTANT:** The same handler can _not_ be added multiple times, even if
* the options differ. If the handler has already been added, it is removed
* and re-added with the current options.
*
* @throws {@link Errors.LisnUsageError | LisnUsageError}
* If the options are invalid.
*/
readonly onLayout: (
handler: OnLayoutHandler,
options?: OnLayoutOptions,
) => Promise<void>;
/**
* Removes a previously added handler.
*/
readonly offLayout: (handler: OnLayoutHandler) => void;
/**
* Get the current screen layout.
*/
readonly fetchCurrentLayout: () => Promise<LayoutData>;
/**
* Creates a new instance of LayoutWatcher with the given
* {@link LayoutWatcherConfig}. It does not save it for future reuse.
*/
static create(config?: LayoutWatcherConfig) {
return new LayoutWatcher(getConfig(config), CONSTRUCTOR_KEY);
}
/**
* Returns an existing instance of LayoutWatcher with the given
* {@link LayoutWatcherConfig}, 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?: LayoutWatcherConfig) {
const myConfig = getConfig(config);
const configStrKey = objToStrKey(omitKeys(myConfig, { _root: null }));
let instance = instances.get(myConfig._root)?.get(configStrKey);
if (!instance) {
instance = new LayoutWatcher(myConfig, CONSTRUCTOR_KEY);
instances.sGet(myConfig._root).set(configStrKey, instance);
}
return instance;
}
private constructor(
config: LayoutWatcherConfigInternal,
key: typeof CONSTRUCTOR_KEY,
) {
if (key !== CONSTRUCTOR_KEY) {
throw MH.illegalConstructorError("LayoutWatcher.create");
}
const logger = debug
? new debug.Logger({ name: "LayoutWatcher", logAtCreation: config })
: null;
let nonIntersectingBitmask = 0;
let currentLayoutData: LayoutData = {
device: null,
aspectRatio: null,
};
const allCallbacks = MH.newMap<
OnLayoutHandler,
{
_callback: OnLayoutCallback;
_layoutBitmask: number;
}
>();
// ----------
const fetchCurrentLayout = async (): Promise<LayoutData> => {
await readyPromise;
return MH.copyObject(currentLayoutData);
};
// ----------
const setupOverlays = async () => {
const { root, overlays } = await createOverlays(
config._root,
config._deviceBreakpoints,
config._aspectRatioBreakpoints,
);
return MH.newPromise<void>((resolve) => {
let isReady = false;
const intersectionHandler = (entries: IntersectionObserverEntry[]) => {
const numEntries = MH.lengthOf(entries);
debug: logger?.debug9(`Got ${numEntries} new entries`, entries);
if (!isReady) {
/* istanbul ignore next */ // shouldn't happen
if (numEntries < NUM_LAYOUTS) {
logWarn(
MH.bugError(
`Got IntersectionObserver ${numEntries}, ` +
`expected >= ${NUM_LAYOUTS}`,
),
);
}
}
for (const entry of entries) {
nonIntersectingBitmask = getNonIntersecting(
nonIntersectingBitmask,
entry,
);
}
// If this is the initial call from IntersectionObserver, skip callbacks.
// Those that have skipInitial: false would be called elsewhere, by
// setupOnLayout
processLayoutChange(!isReady);
isReady = true;
resolve(); // ready after IntersectionObserver has called us the 1st time
};
// ----------
const observeOptions = {
root,
rootMargin: "5px 0% 5px -100%",
};
const observer = MH.newIntersectionObserver(
intersectionHandler,
observeOptions,
);
for (const triggerOverlay of overlays) {
observer.observe(triggerOverlay);
}
});
};
// ----------
const createCallback = (
handler: OnLayoutHandler,
layoutBitmask: number,
): OnLayoutCallback => {
MH.remove(allCallbacks.get(handler)?._callback);
debug: logger?.debug5("Adding/updating handler", layoutBitmask);
const callback = wrapCallback(handler);
callback.onRemove(() => {
deleteHandler(handler);
});
allCallbacks.set(handler, {
_callback: callback,
_layoutBitmask: layoutBitmask,
});
return callback;
};
const setupOnLayout = async (
handler: OnLayoutHandler,
options: OnLayoutOptions | undefined,
) => {
const layoutBitmask = getLayoutBitmask(options);
const callback = createCallback(handler, layoutBitmask);
if (options?.skipInitial) {
return;
}
const layoutData = await fetchCurrentLayout();
if (
!callback.isRemoved() &&
changeMatches(layoutBitmask, layoutData, null)
) {
debug: logger?.debug5("Calling initially with", layoutData);
await invokeCallback(callback, layoutData);
}
};
const deleteHandler = (handler: OnLayoutHandler) => {
MH.deleteKey(allCallbacks, handler);
// no need to unobserve the overlays
};
const processLayoutChange = (skipCallbacks: boolean) => {
const deviceBit = MH.floor(
MH.log2(nonIntersectingBitmask & ORDERED_DEVICES.bitmask),
);
const aspectRatioBit = MH.floor(
MH.log2(nonIntersectingBitmask & ORDERED_ASPECTR.bitmask),
);
const layoutData: LayoutData = { device: null, aspectRatio: null };
// -Infinity means all of the overlays are intersecting, which would only
// happen if the narrowest overlay is not actually 0-width (which is not the
// case by default and against the recommended settings).
if (deviceBit !== -MC.INFINITY) {
layoutData.device = ORDERED_DEVICES.nameOf(1 << deviceBit);
}
if (aspectRatioBit !== -MC.INFINITY) {
layoutData.aspectRatio = ORDERED_ASPECTR.nameOf(1 << aspectRatioBit);
}
debug: logger?.debug8("New layout", layoutData);
if (!skipCallbacks) {
for (const entry of allCallbacks.values()) {
const layoutBitmask = entry._layoutBitmask;
if (!changeMatches(layoutBitmask, layoutData, currentLayoutData)) {
debug: logger?.debug9(
`Layout change does not match bitmask ${layoutBitmask}`,
);
continue;
}
invokeCallback(entry._callback, layoutData);
}
}
currentLayoutData = layoutData;
};
const readyPromise = setupOverlays(); // no need to await
// ----------
this.fetchCurrentLayout = fetchCurrentLayout;
// ----------
this.onLayout = setupOnLayout;
// ----------
this.offLayout = (handler) => {
debug: logger?.debug5("Removing handler");
MH.remove(allCallbacks.get(handler)?._callback);
};
}
}
/**
* @interface
*/
export type LayoutWatcherConfig = {
/**
* The root element whose layout to watch. If not given or `null`, then the
* viewport layout is watched.
*
* @defaultValue null
*/
root?: HTMLElement | null;
/**
* Use custom device breakpoints. Only known device names ({@link Device})
* are supported. If any are missing from the given dictionary, the value
* from {@link settings.deviceBreakpoints} is used.
*
* @defaultValue {@link settings.deviceBreakpoints}
*/
deviceBreakpoints?: typeof settings.deviceBreakpoints;
/**
* Use custom aspect ratio breakpoints. Only known aspect ratio names
* ({@link AspectRatio}) are supported. If any are missing from the given
* dictionary, the value from {@link settings.aspectRatioBreakpoints} is
* used.
*
* @defaultValue {@link settings.aspectRatioBreakpoints}
*/
aspectRatioBreakpoints?: typeof settings.aspectRatioBreakpoints;
};
/**
* @interface
*/
export type OnLayoutOptions = {
/**
* Specifies a list of {@link Device}s to target for.
*
* The handler will only be called if there is a change of device to a device
* matching the specification.
*
* It can be:
* - "min <Device>": devices at least as wide as `<Device>`
* - "max <Device>": devices at most as wide as `<Device>`
* - "<DeviceMin> to <DeviceMax>": devices at least as wide as `<DeviceMin>`
* and at most as wide as `<DeviceMax>`
* - a comma-separated list of device names
* - an array of device names
*
* **NOTE**
*
* If only one of {@link devices} or {@link aspectRatios} is specified, the
* handler will only be called for matching changes of device or aspect ratio
* respectively.
*
* If neither is specified, the handler will be called for any change of layout
* (device or aspect ratio).
*
* Also note that an empty array is treated the same as not given, or `null`.
*
* @defaultValue undefined
*/
devices?: DeviceSpec | Device[];
/**
* Specifies a list of {@link AspectRatio}s to target for.
*
* The handler will only be called if there is a change of aspect ratio to
* an aspect ratios matching the specification.
*
* It can be:
* - "min <AspectRatio>": aspect ratios at least as wide as `<AspectRatio>`
* - "max <AspectRatio>": aspect ratios at most as wide as `<AspectRatio>`
* - "<AspectRatioMin> to <AspectRatioMax>": aspect ratios at least as wide
* as `<AspectRatioMin>` and at most as wide as
* `<AspectRatioMax>`
* - a comma-separated list of aspect ratio names
* - an array of aspect ratio names
*
* **NOTE**
*
* If only one of {@link devices} or {@link aspectRatios} is specified, the
* handler will only be called for matching changes of device or aspect ratio
* respectively.
*
* If neither is specified, the handler will be called for any change of layout
* (device or aspect ratio).
*
* @defaultValue undefined
*/
aspectRatios?: AspectRatioSpec | AspectRatio[];
/**
* Do not call the handler until there's a future change of layout.
*
* By default, we call the handler (almost) immediately with the current
* layout data if it matches the given {@link devices} and {@link aspectRatios}.
*
* @defaultValue false
*/
skipInitial?: boolean;
};
/**
* The handler is invoked with one argument:
*
* - the current {@link LayoutData}
*/
export type OnLayoutHandlerArgs = [LayoutData];
export type OnLayoutCallback = Callback<OnLayoutHandlerArgs>;
export type OnLayoutHandler =
| CallbackHandler<OnLayoutHandlerArgs>
| OnLayoutCallback;
/**
* Note that {@link device} or {@link aspectRatio} would only be null if the
* viewport is narrower than the narrowest device/aspect ratio. This would only
* happen if the narrowest device/aspect ratio is _not_ 0-width (which is not
* the case with the default breakpoints and is against the recommendation for
* setting breakpoints.
*/
export type LayoutData = {
device: Device | null;
aspectRatio: AspectRatio | null;
};
// ----------------------------------------
type LayoutWatcherConfigInternal = {
_root: HTMLElement | null;
_deviceBreakpoints: typeof settings.deviceBreakpoints;
_aspectRatioBreakpoints: typeof settings.aspectRatioBreakpoints;
};
const CONSTRUCTOR_KEY: unique symbol = MC.SYMBOL() as typeof CONSTRUCTOR_KEY;
const instances = newXMap<HTMLElement | null, Map<string, LayoutWatcher>>(() =>
MH.newMap(),
);
const VAR_BORDER_HEIGHT = MH.prefixCssJsVar("border-height");
const PREFIX_DEVICE = MH.prefixName("device");
const PREFIX_ASPECTR = MH.prefixName("aspect-ratio");
const getConfig = (
config: LayoutWatcherConfig | undefined,
): LayoutWatcherConfigInternal => {
const deviceBreakpoints = MH.copyObject(settings.deviceBreakpoints);
if (config?.deviceBreakpoints) {
copyExistingKeys(config.deviceBreakpoints, deviceBreakpoints);
}
const aspectRatioBreakpoints = MH.copyObject(settings.aspectRatioBreakpoints);
if (config?.aspectRatioBreakpoints) {
copyExistingKeys(config.aspectRatioBreakpoints, aspectRatioBreakpoints);
}
return {
_root: config?.root ?? null,
_deviceBreakpoints: deviceBreakpoints,
_aspectRatioBreakpoints: aspectRatioBreakpoints,
};
};
// ----------------------------------------
const createOverlays = async (
root: HTMLElement | null,
deviceBreakpoints: typeof settings.deviceBreakpoints,
aspectRatioBreakpoints: typeof settings.aspectRatioBreakpoints,
) => {
const overlayPromises = [];
let overlayParent: HTMLElement;
if (root) {
overlayParent = root;
} else {
// Since modals remove the scrollbar on the body when active, the width of
// the body changes upon open/close of a modal, which would create
// glitching if it happens near a device breakpoint. So if the root is the
// viewport, we create a fixed positioned container to hold the overlays
// and set its width to be 100vw and use that as the root of
overlayParent = await createOverlay({
style: {
position: "fixed",
[MC.S_WIDTH]: "100vw",
},
});
}
let device: Device;
for (device in deviceBreakpoints) {
overlayPromises.push(
createOverlay({
parent: overlayParent,
style: {
position: "absolute",
[MC.S_WIDTH]: deviceBreakpoints[device] + "px",
},
data: {
[PREFIX_DEVICE]: device,
},
}),
);
}
const parentHeightCss = root ? `var(${VAR_BORDER_HEIGHT}, 0) * 1px` : "100vh";
if (root) {
SizeWatcher.reuse().trackSize(null, { target: root });
}
let aspectRatio: AspectRatio;
for (aspectRatio in aspectRatioBreakpoints) {
overlayPromises.push(
createOverlay({
parent: overlayParent,
style: {
position: "absolute",
[MC.S_WIDTH]:
`calc(${aspectRatioBreakpoints[aspectRatio]} ` +
`* ${parentHeightCss})`,
},
data: {
[PREFIX_ASPECTR]: aspectRatio,
},
}),
);
}
const overlays = await MH.promiseAll(overlayPromises);
return { root: overlayParent, overlays };
};
const getOverlayLayout = (overlay: HTMLElement): Layout | null => {
const layout =
getData(overlay, PREFIX_DEVICE) || getData(overlay, PREFIX_ASPECTR);
/* istanbul ignore else */
if (layout && (ORDERED_DEVICES.has(layout) || ORDERED_ASPECTR.has(layout))) {
return layout;
} else {
// shouldn't happen
logError(MH.bugError("No device or aspectRatio data attribute"));
return null;
}
};
const changeMatches = (
layoutBitmask: number,
thisLayoutData: LayoutData,
prevLayoutData: LayoutData | undefined | null,
): boolean => {
// True if the callback is interested in a change of device and there's a
// change of device and the new device is one of the ones it's interested in
// (or it's null, i.e. device is undefined).
// And the same for aspect ratios.
if (
prevLayoutData?.device !== thisLayoutData.device &&
(!thisLayoutData.device ||
ORDERED_DEVICES.bit[thisLayoutData.device] & layoutBitmask)
) {
return true;
}
if (
prevLayoutData?.aspectRatio !== thisLayoutData.aspectRatio &&
(!thisLayoutData.aspectRatio ||
ORDERED_ASPECTR.bit[thisLayoutData.aspectRatio] & layoutBitmask)
) {
return true;
}
return false;
};
const getNonIntersecting = (
nonIntersectingBitmask: number, // current
entry: IntersectionObserverEntry,
): number => {
const target = MH.targetOf(entry);
/* istanbul ignore next */ // shouldn't happen
if (!MH.isHTMLElement(target)) {
logError(
MH.bugError(
`IntersectionObserver called us with '${MH.typeOrClassOf(target)}'`,
),
);
return nonIntersectingBitmask;
}
const layout = getOverlayLayout(target);
let bit = 0;
Iif (!layout) {
// error already logged by getOverlayLayout
} else if (ORDERED_DEVICES.has(layout)) {
bit = ORDERED_DEVICES.bit[layout];
} else if (ORDERED_ASPECTR.has(layout)) {
bit = ORDERED_ASPECTR.bit[layout];
} else E{
/* istanbul ignore next */ // shouldn't happen
logError(
MH.bugError(`Unknown device or aspectRatio data attribute: ${layout}`),
);
}
if (entry.isIntersecting) {
nonIntersectingBitmask &= ~bit;
} else {
nonIntersectingBitmask |= bit;
}
return nonIntersectingBitmask;
};
const invokeCallback = (callback: OnLayoutCallback, layoutData: LayoutData) =>
callback.invoke(MH.copyObject(layoutData)).catch(logError);
|