leaflet-tilelayer-vector/TileCache.js at dev · nrenner/leaflet-tilelayer-vector · GitHub

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/**
 * Simple tile cache to keep tiles while zooming with overzoom
 */
L.TileCache = function() {
};

L.TileCache.prototype = {
    // cache key: tile (String: Object)
    _cache: {},

    // flag to determine switch between tile unloading (put) and loading (get) phase
    _unloading: false,

    // flag to only cache tiles when zooming, not when moving
    _zooming: false,

    onAdd: function(map) {
        this._map = map;

        map.on('zoomstart', this._onZoomStart, this);
        map.on('zoomend', this._onZoomEnd, this);
    },

    onRemove: function(map) {
        this._map = null;

        map.off('zoomstart', this._onZoomStart, this);
        map.off('zoomend', this._onZoomEnd, this);
    },

    _onZoomStart: function(evt) {
        this._zooming = true;
    },

    _onZoomEnd: function(evt) {
        this._zooming = false;
    },

    get: function(key, urlZoom) {
        var ckey = this._getCacheKey(key, urlZoom);
        var tile = this._cache[ckey];
        this._unloading = false;
        //console.log('cache ' + (tile ? 'hit ' : 'miss') + ': ' + ckey);
        return tile;
    },

    put: function(tile) {
        if (!this._zooming) return;

        if (!this._unloading) {
            // clear old entries before adding newly removed tiles after zoom or move
            this.clear();
            this._unloading = true;
        }

        var ckey = this._getCacheKeyFromTile(tile);
        if (!(ckey in this._cache)) {
            // vector layer is recreated because of feature filter
            delete tile.layer;
            this._cache[ckey] = tile;
            //console.log('cache put : ' + ckey + ' (' + Object.keys(this._cache).length + ')');
        }
    },

    clear: function() {
        //console.log('cache clear');
        this._cache = {};
    },

    _getCacheKeyFromTile: function(tile) {
        return this._getCacheKey(tile.key, tile.urlZoom);
    },

    _getCacheKey: function(key, urlZoom) {
        return urlZoom + ':' + key
    }
};

L.tileCache = function() {
    return new L.TileCache();
};

// dummy impl. to turn caching off
L.tileCacheNone = function() {
    return {
        onAdd: function(map) {},
        onRemove: function(map) {},
        get: function(key, urlZoom) {},
        put: function(tile) {},
        clear: function() {}
    };
};