source_cache.js

// @flow

const createSource = require('./source').create;
const Tile = require('./tile');
const Evented = require('../util/evented');
const Cache = require('../util/lru_cache');
const Coordinate = require('../geo/coordinate');
const util = require('../util/util');
const EXTENT = require('../data/extent');
const Context = require('../gl/context');
const Point = require('@mapbox/point-geometry');
const browser = require('../util/browser');
const {OverscaledTileID} = require('./tile_id');
const assert = require('assert');

import type {Source} from './source';
import type Map from '../ui/map';
import type Style from '../style/style';
import type Dispatcher from '../util/dispatcher';
import type Transform from '../geo/transform';
import type {TileState} from './tile';
import type CollisionIndex from '../symbol/collision_index';
import type {Callback} from '../types/callback';

/**
 * `SourceCache` is responsible for
 *
 *  - creating an instance of `Source`
 *  - forwarding events from `Source`
 *  - caching tiles loaded from an instance of `Source`
 *  - loading the tiles needed to render a given viewport
 *  - unloading the cached tiles not needed to render a given viewport
 *
 * @private
 */
class SourceCache extends Evented {
    id: string;
    dispatcher: Dispatcher;
    map: Map;
    style: Style;

    _source: Source;
    _sourceLoaded: boolean;
    _sourceErrored: boolean;
    _tiles: {[any]: Tile};
    _cache: Cache<Tile>;
    _timers: {[any]: number};
    _cacheTimers: {[any]: number};
    _maxTileCacheSize: ?number;
    _paused: boolean;
    _shouldReloadOnResume: boolean;
    _needsFullPlacement: boolean;
    _coveredTiles: {[any]: boolean};
    transform: Transform;
    _isIdRenderable: (id: number) => boolean;
    used: boolean;

    static maxUnderzooming: number;
    static maxOverzooming: number;

    constructor(id: string, options: SourceSpecification, dispatcher: Dispatcher) {
        super();
        this.id = id;
        this.dispatcher = dispatcher;

        this.on('data', (e) => {
            // this._sourceLoaded signifies that the TileJSON is loaded if applicable.
            // if the source type does not come with a TileJSON, the flag signifies the
            // source data has loaded (i.e geojson has been tiled on the worker and is ready)
            if (e.dataType === 'source' && e.sourceDataType === 'metadata') this._sourceLoaded = true;

            // for sources with mutable data, this event fires when the underlying data
            // to a source is changed. (i.e. GeoJSONSource#setData and ImageSource#serCoordinates)
            if (this._sourceLoaded && !this._paused && e.dataType === "source" && e.sourceDataType === 'content') {
                this.reload();
                if (this.transform) {
                    this.update(this.transform);
                }
            }
        });

        this.on('error', () => {
            this._sourceErrored = true;
        });

        this._source = createSource(id, options, dispatcher, this);

        this._tiles = {};
        this._cache = new Cache(0, this._unloadTile.bind(this));
        this._timers = {};
        this._cacheTimers = {};
        this._maxTileCacheSize = null;

        this._isIdRenderable = this._isIdRenderable.bind(this);

        this._coveredTiles = {};
    }

    onAdd(map: Map) {
        this.map = map;
        this._maxTileCacheSize = map ? map._maxTileCacheSize : null;
        if (this._source && this._source.onAdd) {
            this._source.onAdd(map);
        }
    }

    onRemove(map: Map) {
        if (this._source && this._source.onRemove) {
            this._source.onRemove(map);
        }
    }

    /**
     * Return true if no tile data is pending, tiles will not change unless
     * an additional API call is received.
     */
    loaded(): boolean {
        if (this._sourceErrored) { return true; }
        if (!this._sourceLoaded) { return false; }
        for (const t in this._tiles) {
            const tile = this._tiles[t];
            if (tile.state !== 'loaded' && tile.state !== 'errored')
                return false;
        }
        return true;
    }

    getSource(): Source {
        return this._source;
    }

    pause() {
        this._paused = true;
    }

    getNeedsFullPlacement() {
        return this._needsFullPlacement;
    }

    resume() {
        if (!this._paused) return;
        const shouldReload = this._shouldReloadOnResume;
        this._paused = false;
        this._shouldReloadOnResume = false;
        if (shouldReload) this.reload();
        if (this.transform) this.update(this.transform);
    }

    _loadTile(tile: Tile, callback: Callback<void>) {
        return this._source.loadTile(tile, callback);
    }

    _unloadTile(tile: Tile) {
        if (this._source.unloadTile)
            return this._source.unloadTile(tile, () => {});
    }

    _abortTile(tile: Tile) {
        if (this._source.abortTile)
            return this._source.abortTile(tile, () => {});
    }

    serialize() {
        return this._source.serialize();
    }

    prepare(context: Context) {
        if  (this._source.prepare) {
            this._source.prepare();
        }

        for (const i in this._tiles) {
            this._tiles[i].upload(context);
        }
    }

    /**
     * Return all tile ids ordered with z-order, and cast to numbers
     */
    getIds(): Array<number> {

        const compareKeyZoom = (a_, b_) => {
            const a = this._tiles[a_].tileID;
            const b = this._tiles[b_].tileID;
            const rotatedA = (new Point(a.canonical.x, a.canonical.y)).rotate(this.transform.angle);
            const rotatedB = (new Point(b.canonical.x, b.canonical.y)).rotate(this.transform.angle);
            return a.overscaledZ - b.overscaledZ || rotatedB.y - rotatedA.y || rotatedB.x - rotatedA.x;
        };

        return Object.keys(this._tiles).map(Number).sort(compareKeyZoom);
    }

    getRenderableIds() {
        return this.getIds().filter(this._isIdRenderable);
    }

    hasRenderableParent(tileID: OverscaledTileID) {
        const parentTile = this.findLoadedParent(tileID, 0, {});
        if (parentTile) {
            return this._isIdRenderable(parentTile.tileID.key);
        }
        return false;
    }

    _isIdRenderable(id: number) {
        return this._tiles[id] && this._tiles[id].hasData() && !this._coveredTiles[id];
    }

    reload() {
        if (this._paused) {
            this._shouldReloadOnResume = true;
            return;
        }

        this._cache.reset();
        for (const i in this._tiles) {
            this._reloadTile(i, 'reloading');
        }
    }

    _reloadTile(id: string | number, state: TileState) {
        const tile = this._tiles[id];

        // this potentially does not address all underlying
        // issues https://github.com/mapbox/mapbox-gl-js/issues/4252
        // - hard to tell without repro steps
        if (!tile) return;

        // The difference between "loading" tiles and "reloading" or "expired"
        // tiles is that "reloading"/"expired" tiles are "renderable".
        // Therefore, a "loading" tile cannot become a "reloading" tile without
        // first becoming a "loaded" tile.
        if (tile.state !== 'loading') {
            tile.state = state;
        }

        this._loadTile(tile, this._tileLoaded.bind(this, tile, id, state));
    }

    _tileLoaded(tile: Tile, id: string | number, previousState: TileState, err: ?Error) {
        if (err) {
            tile.state = 'errored';
            if (err.status !== 404) this._source.fire('error', {tile: tile, error: err});
            // continue to try loading parent/children tiles if a tile doesn't exist (404)
            else this.update(this.transform);
            return;
        }

        tile.timeAdded = browser.now();
        if (previousState === 'expired') tile.refreshedUponExpiration = true;
        this._setTileReloadTimer(id, tile);
        if (this.getSource().type === 'raster-dem' && tile.dem) this._backfillDEM(tile);
        this._source.fire('data', {dataType: 'source', tile: tile, coord: tile.tileID});

        // HACK this is necessary to fix https://github.com/mapbox/mapbox-gl-js/issues/2986
        if (this.map) this.map.painter.tileExtentVAO.vao = null;

        this._updatePlacement();
        if (this.map && this.getTileByID(id)) {
            // Only add this tile to the CrossTileSymbolIndex if it is still in the retain set
            // See issue #5837
            tile.added(this.map.painter.crossTileSymbolIndex);
        }
    }

    /**
    * For raster terrain source, backfill DEM to eliminate visible tile boundaries
    * @private
    */
    _backfillDEM(tile: Tile) {
        const renderables = this.getRenderableIds();
        for (let i = 0; i < renderables.length; i++) {
            const borderId = renderables[i];
            if (tile.neighboringTiles && tile.neighboringTiles[borderId]) {
                const borderTile = this.getTileByID(borderId);
                fillBorder(tile, borderTile);
                fillBorder(borderTile, tile);
            }
        }

        function fillBorder(tile, borderTile) {
            tile.needsHillshadePrepare = true;
            let dx = borderTile.tileID.canonical.x - tile.tileID.canonical.x;
            const dy = borderTile.tileID.canonical.y - tile.tileID.canonical.y;
            const dim = Math.pow(2, tile.tileID.canonical.z);
            const borderId = borderTile.tileID.key;
            if (dx === 0 && dy === 0) return;

            if (Math.abs(dy) > 1) {
                return;
            }
            if (Math.abs(dx) > 1) {
                // Adjust the delta coordinate for world wraparound.
                if (Math.abs(dx + dim) === 1) {
                    dx += dim;
                } else if (Math.abs(dx - dim) === 1) {
                    dx -= dim;
                }
            }
            if (!borderTile.dem || !tile.dem) return;
            tile.dem.backfillBorder(borderTile.dem, dx, dy);
            if (tile.neighboringTiles && tile.neighboringTiles[borderId])
                tile.neighboringTiles[borderId].backfilled = true;
        }
    }
    /**
     * Get a specific tile by TileID
     */
    getTile(tileID: OverscaledTileID): Tile {
        return this.getTileByID(tileID.key);
    }

    /**
     * Get a specific tile by id
     */
    getTileByID(id: string | number): Tile {
        return this._tiles[id];
    }

    /**
     * get the zoom level adjusted for the difference in map and source tilesizes
     */
    getZoom(transform: Transform): number {
        return transform.zoom + transform.scaleZoom(transform.tileSize / this._source.tileSize);
    }

    /**
     * Recursively find children of the given tile (up to maxCoveringZoom) that are already loaded;
     * adds found tiles to retain object; returns true if any child is found.
     */
    _findLoadedChildren(tileID: OverscaledTileID, maxCoveringZoom: number, retain: {[any]: OverscaledTileID}): boolean {
        let found = false;

        for (const id in this._tiles) {
            let tile = this._tiles[id];

            // only consider renderable tiles on higher zoom levels (up to maxCoveringZoom)
            if (retain[id] || !tile.hasData() || tile.tileID.overscaledZ <= tileID.overscaledZ || tile.tileID.overscaledZ > maxCoveringZoom) continue;

            // disregard tiles that are not descendants of the given tile coordinate
            const z2 = Math.pow(2, tile.tileID.canonical.z - tileID.canonical.z);
            if (Math.floor(tile.tileID.canonical.x / z2) !== tileID.canonical.x ||
                Math.floor(tile.tileID.canonical.y / z2) !== tileID.canonical.y)
                continue;

            // found loaded child
            retain[id] = tile.tileID;
            found = true;

            // loop through parents; retain the topmost loaded one if found
            while (tile && tile.tileID.overscaledZ - 1 > tileID.overscaledZ) {
                const parent = tile.tileID.scaledTo(tile.tileID.overscaledZ - 1);
                if (!parent) break;

                tile = this._tiles[parent.key];
                if (tile && tile.hasData()) {
                    delete retain[id];
                    retain[parent.key] = parent;
                }
            }
        }
        return found;
    }

    /**
     * Find a loaded parent of the given tile (up to minCoveringZoom);
     * adds the found tile to retain object and returns the tile if found
     */
    findLoadedParent(tileID: OverscaledTileID, minCoveringZoom: number, retain: {[any]: OverscaledTileID}): ?Tile {
        for (let z = tileID.overscaledZ - 1; z >= minCoveringZoom; z--) {
            const parent = tileID.scaledTo(z);
            if (!parent) return;
            const id = String(parent.key);
            const tile = this._tiles[id];
            if (tile && tile.hasData()) {
                retain[id] = parent;
                return tile;
            }
            if (this._cache.has(id)) {
                retain[id] = parent;
                return this._cache.get(id);
            }
        }
    }

    /**
     * Resizes the tile cache based on the current viewport's size
     * or the maxTileCacheSize option passed during map creation
     *
     * Larger viewports use more tiles and need larger caches. Larger viewports
     * are more likely to be found on devices with more memory and on pages where
     * the map is more important.
     */
    updateCacheSize(transform: Transform) {
        const widthInTiles = Math.ceil(transform.width / this._source.tileSize) + 1;
        const heightInTiles = Math.ceil(transform.height / this._source.tileSize) + 1;
        const approxTilesInView = widthInTiles * heightInTiles;
        const commonZoomRange = 5;

        const viewDependentMaxSize = Math.floor(approxTilesInView * commonZoomRange);
        const maxSize = typeof this._maxTileCacheSize === 'number' ? Math.min(this._maxTileCacheSize, viewDependentMaxSize) : viewDependentMaxSize;

        this._cache.setMaxSize(maxSize);
    }

    /**
     * Removes tiles that are outside the viewport and adds new tiles that
     * are inside the viewport.
     */
    update(transform: Transform) {
        this.transform = transform;
        if (!this._sourceLoaded || this._paused) { return; }

        this.updateCacheSize(transform);
        // Covered is a list of retained tiles who's areas are fully covered by other,
        // better, retained tiles. They are not drawn separately.
        this._coveredTiles = {};

        let idealTileIDs;
        if (!this.used) {
            idealTileIDs = [];
        } else if (this._source.tileID) {
            idealTileIDs = transform.getVisibleUnwrappedCoordinates((this._source.tileID: any))
                .map((unwrapped) => new OverscaledTileID(unwrapped.canonical.z, unwrapped.wrap, unwrapped.canonical.z, unwrapped.canonical.x, unwrapped.canonical.y));
        } else {
            idealTileIDs = transform.coveringTiles({
                tileSize: this._source.tileSize,
                minzoom: this._source.minzoom,
                maxzoom: this._source.maxzoom,
                roundZoom: this._source.roundZoom,
                reparseOverscaled: this._source.reparseOverscaled
            });

            if (this._source.hasTile) {
                idealTileIDs = idealTileIDs.filter((coord) => (this._source.hasTile: any)(coord));
            }
        }

        // Determine the overzooming/underzooming amounts.
        const zoom = (this._source.roundZoom ? Math.round : Math.floor)(this.getZoom(transform));
        const minCoveringZoom = Math.max(zoom - SourceCache.maxOverzooming, this._source.minzoom);
        const maxCoveringZoom = Math.max(zoom + SourceCache.maxUnderzooming,  this._source.minzoom);

        // Retain is a list of tiles that we shouldn't delete, even if they are not
        // the most ideal tile for the current viewport. This may include tiles like
        // parent or child tiles that are *already* loaded.
        const retain = this._updateRetainedTiles(idealTileIDs, zoom);

        const parentsForFading = {};

        if (isRasterType(this._source.type)) {
            const ids = Object.keys(retain);
            for (let k = 0; k < ids.length; k++) {
                const id = ids[k];
                const tileID = retain[id];
                assert(tileID.key === +id);
                const tile = this._tiles[id];
                if (!tile) continue;

                // If the drawRasterTile has never seen this tile, then
                // tile.fadeEndTime may be unset.  In that case, or if
                // fadeEndTime is in the future, then this tile is still
                // fading in. Find tiles to cross-fade with it.
                if (typeof tile.fadeEndTime === 'undefined' || tile.fadeEndTime >= browser.now()) {
                    if (this._findLoadedChildren(tileID, maxCoveringZoom, retain)) {
                        retain[id] = tileID;
                    }
                    const parentTile = this.findLoadedParent(tileID, minCoveringZoom, parentsForFading);
                    if (parentTile) {
                        this._addTile(parentTile.tileID);
                    }
                }
            }
        }

        let fadedParent;
        for (fadedParent in parentsForFading) {
            if (!retain[fadedParent]) {
                // If a tile is only needed for fading, mark it as covered so that it isn't rendered on it's own.
                this._coveredTiles[fadedParent] = true;
            }
        }
        for (fadedParent in parentsForFading) {
            retain[fadedParent] = parentsForFading[fadedParent];
        }
        // Remove the tiles we don't need anymore.
        const remove = util.keysDifference(this._tiles, retain);
        for (let i = 0; i < remove.length; i++) {
            this._removeTile(remove[i]);
        }
    }

    _updateRetainedTiles(idealTileIDs: Array<OverscaledTileID>, zoom: number): { [string]: OverscaledTileID} {
        const retain = {};
        const checked: {[number]: boolean } = {};
        const minCoveringZoom = Math.max(zoom - SourceCache.maxOverzooming, this._source.minzoom);
        const maxCoveringZoom = Math.max(zoom + SourceCache.maxUnderzooming,  this._source.minzoom);

        for (let i = 0; i < idealTileIDs.length; i++) {
            const tileID = idealTileIDs[i];
            let tile = this._addTile(tileID);
            let parentWasRequested = false;
            if (tile.hasData()) {
                retain[tileID.key] = tileID;
            } else {
                // The tile we require is not yet loaded or does not exist.
                // We are now attempting to load child and parent tiles.

                // As we descend up and down the tile pyramid of the ideal tile, we check whether the parent
                // tile has been previously requested (and errored in this case due to the previous conditional)
                // in order to determine if we need to request its parent.
                parentWasRequested = tile.wasRequested();

                // The tile isn't loaded yet, but retain it anyway because it's an ideal tile.
                retain[tileID.key] = tileID;
                let covered = true;
                const overscaledZ = zoom + 1;
                if (overscaledZ > this._source.maxzoom) {
                    // We're looking for an overzoomed child tile.
                    const childCoord = tileID.children(this._source.maxzoom)[0];
                    const childTile = this.getTile(childCoord);
                    if (!!childTile && childTile.hasData()) {
                        retain[childCoord.key] = childCoord;
                    } else {
                        covered = false;
                    }
                } else {
                    this._findLoadedChildren(tileID, maxCoveringZoom, retain);
                    // check if all 4 immediate children are loaded (i.e. the missing ideal tile is covered)
                    const children = tileID.children(this._source.maxzoom);
                    for (let j = 0; j < children.length; j++) {
                        if (!retain[children[j].key]) {
                            covered = false;
                            break;
                        }
                    }
                }

                if (!covered) {

                    // We couldn't find child tiles that entirely cover the ideal tile.
                    for (let overscaledZ = tileID.overscaledZ - 1; overscaledZ >= minCoveringZoom; --overscaledZ) {

                        const parentId = tileID.scaledTo(overscaledZ);
                        if (checked[parentId.key]) {
                            // Break parent tile ascent, this route has been previously checked by another child.
                            break;
                        } else {
                            checked[parentId.key] = true;
                        }

                        tile = this.getTile(parentId);
                        if (!tile && parentWasRequested) {
                            tile = this._addTile(parentId);
                        }

                        if (tile) {
                            retain[parentId.key] = parentId;
                            // Save the current values, since they're the parent of the next iteration
                            // of the parent tile ascent loop.
                            parentWasRequested = tile.wasRequested();
                            if (tile.hasData()) {
                                break;
                            }
                        }
                    }
                }
            }
        }

        return retain;
    }

    /**
     * Add a tile, given its coordinate, to the pyramid.
     * @private
     */
    _addTile(tileID: OverscaledTileID): Tile {
        let tile = this._tiles[tileID.key];
        if (tile)
            return tile;


        tile = this._cache.getAndRemove((tileID.key: any));
        if (tile) {
            this._updatePlacement();
            if (this.map)
                tile.added(this.map.painter.crossTileSymbolIndex);
            if (this._cacheTimers[tileID.key]) {
                clearTimeout(this._cacheTimers[tileID.key]);
                delete this._cacheTimers[tileID.key];
                this._setTileReloadTimer(tileID.key, tile);
            }
        }

        const cached = Boolean(tile);
        if (!cached) {
            tile = new Tile(tileID, this._source.tileSize * tileID.overscaleFactor());
            this._loadTile(tile, this._tileLoaded.bind(this, tile, tileID.key, tile.state));
        }

        // Impossible, but silence flow.
        if (!tile) return (null: any);

        tile.uses++;
        this._tiles[tileID.key] = tile;
        if (!cached) this._source.fire('dataloading', {tile: tile, coord: tile.tileID, dataType: 'source'});

        return tile;
    }

    _setTileReloadTimer(id: string | number, tile: Tile) {
        const expiryTimeout = tile.getExpiryTimeout();
        if (expiryTimeout) {
            this._timers[id] = setTimeout(() => {
                this._reloadTile(id, 'expired');
                delete this._timers[id];
            }, expiryTimeout);
        }
    }

    _setCacheInvalidationTimer(id: string | number, tile: Tile) {
        const expiryTimeout = tile.getExpiryTimeout();
        if (expiryTimeout) {
            this._cacheTimers[id] = setTimeout(() => {
                this._cache.remove((id: any));
                delete this._cacheTimers[id];
            }, expiryTimeout);
        }
    }

    /**
     * Remove a tile, given its id, from the pyramid
     * @private
     */
    _removeTile(id: string | number) {
        const tile = this._tiles[id];
        if (!tile)
            return;

        tile.uses--;
        delete this._tiles[id];
        if (this._timers[id]) {
            clearTimeout(this._timers[id]);
            delete this._timers[id];
        }

        if (tile.uses > 0)
            return;

        this._updatePlacement();
        if (this.map)
            tile.removed(this.map.painter.crossTileSymbolIndex);

        if (tile.hasData()) {
            tile.tileID = tile.tileID.wrapped();
            const wrappedId = tile.tileID.key;
            this._cache.add((wrappedId: any), tile);
            this._setCacheInvalidationTimer(wrappedId, tile);
        } else {
            tile.aborted = true;
            this._abortTile(tile);
            this._unloadTile(tile);
        }
    }

    _updatePlacement() {
        this._needsFullPlacement = true;
    }

    /**
     * Remove all tiles from this pyramid
     */
    clearTiles() {
        this._shouldReloadOnResume = false;
        this._paused = false;

        for (const id in this._tiles)
            this._removeTile(id);
        this._cache.reset();
    }

    /**
     * Search through our current tiles and attempt to find the tiles that
     * cover the given bounds.
     * @param queryGeometry coordinates of the corners of bounding rectangle
     * @returns {Array<Object>} result items have {tile, minX, maxX, minY, maxY}, where min/max bounding values are the given bounds transformed in into the coordinate space of this tile.
     */
    tilesIn(queryGeometry: Array<Coordinate>) {
        const tileResults = [];
        const ids = this.getIds();

        let minX = Infinity;
        let minY = Infinity;
        let maxX = -Infinity;
        let maxY = -Infinity;
        const z = queryGeometry[0].zoom;

        for (let k = 0; k < queryGeometry.length; k++) {
            const p = queryGeometry[k];
            minX = Math.min(minX, p.column);
            minY = Math.min(minY, p.row);
            maxX = Math.max(maxX, p.column);
            maxY = Math.max(maxY, p.row);
        }


        for (let i = 0; i < ids.length; i++) {
            const tile = this._tiles[ids[i]];
            const tileID = tile.tileID;

            const tileSpaceBounds = [
                coordinateToTilePoint(tileID, new Coordinate(minX, minY, z)),
                coordinateToTilePoint(tileID, new Coordinate(maxX, maxY, z))
            ];

            if (tileSpaceBounds[0].x < EXTENT && tileSpaceBounds[0].y < EXTENT &&
                tileSpaceBounds[1].x >= 0 && tileSpaceBounds[1].y >= 0) {

                const tileSpaceQueryGeometry = [];
                for (let j = 0; j < queryGeometry.length; j++) {
                    tileSpaceQueryGeometry.push(coordinateToTilePoint(tileID, queryGeometry[j]));
                }

                tileResults.push({
                    tile: tile,
                    tileID: tileID,
                    queryGeometry: [tileSpaceQueryGeometry],
                    scale: Math.pow(2, this.transform.zoom - tile.tileID.overscaledZ)
                });
            }
        }

        return tileResults;
    }

    commitPlacement(collisionIndex: CollisionIndex, collisionFadeTimes: any) {
        this._needsFullPlacement = false;
        const ids = this.getIds();
        for (let i = 0; i < ids.length; i++) {
            const tile = this.getTileByID(ids[i]);
            tile.commitPlacement(collisionIndex, collisionFadeTimes, this.transform.angle);
        }
    }

    getVisibleCoordinates() {
        const coords = this.getRenderableIds().map((id) => this._tiles[id].tileID);
        for (const coord of coords) {
            coord.posMatrix = this.transform.calculatePosMatrix(coord.toUnwrapped());
        }
        return coords;
    }

    hasTransition() {
        if (this._source.hasTransition()) {
            return true;
        }

        if (isRasterType(this._source.type)) {
            for (const id in this._tiles) {
                const tile = this._tiles[id];
                if (tile.fadeEndTime !== undefined && tile.fadeEndTime >= browser.now()) {
                    return true;
                }
            }
        }

        return false;
    }
}

SourceCache.maxOverzooming = 10;
SourceCache.maxUnderzooming = 3;

/**
 * Convert a coordinate to a point in a tile's coordinate space.
 * @private
 */
function coordinateToTilePoint(tileID: OverscaledTileID, coord: Coordinate): Point {
    const zoomedCoord = coord.zoomTo(tileID.canonical.z);
    return new Point(
        (zoomedCoord.column - (tileID.canonical.x + tileID.wrap * Math.pow(2, tileID.canonical.z))) * EXTENT,
        (zoomedCoord.row - tileID.canonical.y) * EXTENT
    );
}

function isRasterType(type) {
    return type === 'raster' || type === 'image' || type === 'video';
}

module.exports = SourceCache;