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tile_pyramid.js
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tile_pyramid.js
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'use strict';
var Source = require('./source');
var Tile = require('./tile');
var Evented = require('../util/evented');
var TileCoord = require('./tile_coord');
var Cache = require('../util/lru_cache');
var Coordinate = require('../geo/coordinate');
var util = require('../util/util');
var EXTENT = require('../data/bucket').EXTENT;
module.exports = TilePyramid;
/**
* A tile pyramid is a specialized cache and datastructure
* that contains tiles. It's used by sources to manage their
* data.
*
* @param {Object} options
* @private
*/
function TilePyramid(id, options, dispatcher) {
this.id = id;
this.dispatcher = dispatcher;
var onChange = function () {
this.sourceChangedSoWeShouldUpdatePyramidNow();
}.bind(this);
// TODO: this is an ugly consequence of inverting tilepyramid / source
// dependency and making source creation async: we use a dumb, generic
// version of serialize() until the source is loaded at which point we
// switch to deferring to the source's method.
// Options:
// 1. Make Source.create synchronous. Drawback: would require adding `loaded()` or `onLoad` to the Source interface.
// 2. Remove Source:serialize() entirely, and instead let TilePyramid:serialize() always jut return the options object it was created with.
// 3. Leave the below wart as-is.
// I prefer option 2 if it's workable.
this.serialize = function () { return options; };
var sourceLoaded = function (err, source) {
if (err) {
this.fire('error', {error: err});
return;
}
// TODO: remove this once we eliminate need for sources to have a
// reference to the Map instance.
this._source = source;
if (this.map) { source.map = this.map; }
this._sourceLoaded = true;
this.tileSize = source.tileSize;
this.minzoom = source.minzoom;
this.maxzoom = source.maxzoom;
// TODO: not exactly sure on these three properties and whether they
// make sense as part of the Source interface.
this.roundZoom = source.roundZoom;
this.reparseOverscaled = source.reparseOverscaled;
this.isTileClipped = source.isTileClipped;
// TODO: what's cleaner? 1) grab references to the Source methods we
// want, or 2) just keep a reference to the Source itself and delegate?
var noop = function () {};
this._load = (source.load || noop).bind(source);
this._abort = (source.abort || noop).bind(source);
this._unload = (source.unload || noop).bind(source);
this.serialize = (source.serialize || noop).bind(source);
this.fire('load');
}.bind(this);
Source.create(id, options, dispatcher, onChange, sourceLoaded);
this._tiles = {};
this._cache = new Cache(0, function(tile) { return this._unload(tile); }.bind(this));
this._filterRendered = this._filterRendered.bind(this);
}
TilePyramid.maxOverzooming = 10;
TilePyramid.maxUnderzooming = 3;
TilePyramid.prototype = util.inherit(Evented, {
// TODO: hopefully remove the need for this
onAdd: function (map) {
this.map = map;
if (this._source) { this._source.map = map; }
},
/**
* Confirm that every tracked tile is loaded.
* @returns {boolean} whether all tiles are loaded.
* @private
*/
loaded: function() {
if (!this._sourceLoaded) { return false; }
for (var t in this._tiles) {
if (!this._tiles[t].loaded && !this._tiles[t].errored)
return false;
}
return true;
},
/**
* Return all tile ids ordered with z-order, and cast to numbers
* @returns {Array<number>} ids
* @private
*/
orderedIDs: function() {
return Object.keys(this._tiles).map(Number).sort(compareKeyZoom);
},
renderedIDs: function() {
return this.orderedIDs().filter(this._filterRendered);
},
_filterRendered: function(id) {
return this._tiles[id].loaded && !this._coveredTiles[id];
},
reload: function() {
this._cache.reset();
for (var i in this._tiles) {
this._load(this._tiles[i], this._tileLoaded.bind(this, this._tiles[i]));
}
},
_tileLoaded: function (tile, err, data) {
if (err) {
tile.errored = true;
this.fire('tile.error', {tile: tile, error: err});
return;
}
this.fire('tile.load', {tile: tile});
if (data && data.bucketStats) {
this.fire('tile.stats', data.bucketStats);
}
},
/**
* Get a specific tile by TileCoordinate
* @param {TileCoordinate} coord
* @returns {Object} tile
* @private
*/
getTile: function(coord) {
return this.getTileByID(coord.id);
},
/**
* Get a specific tile by id
* @param {number|string} id
* @returns {Object} tile
* @private
*/
getTileByID: function(id) {
return this._tiles[id];
},
/**
* get the zoom level adjusted for the difference in map and source tilesizes
* @param {Object} transform
* @returns {number} zoom level
* @private
*/
getZoom: function(transform) {
return transform.zoom + transform.scaleZoom(transform.tileSize / this.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.
*
* @param {Coordinate} coord
* @param {number} maxCoveringZoom
* @param {boolean} retain
* @returns {boolean} whether the operation was complete
* @private
*/
findLoadedChildren: function(coord, maxCoveringZoom, retain) {
var found = false;
for (var id in this._tiles) {
var tile = this._tiles[id];
// only consider loaded tiles on higher zoom levels (up to maxCoveringZoom)
if (retain[id] || !tile.loaded || tile.coord.z <= coord.z || tile.coord.z > maxCoveringZoom) continue;
// disregard tiles that are not descendants of the given tile coordinate
var z2 = Math.pow(2, Math.min(tile.coord.z, this.maxzoom) - Math.min(coord.z, this.maxzoom));
if (Math.floor(tile.coord.x / z2) !== coord.x ||
Math.floor(tile.coord.y / z2) !== coord.y)
continue;
// found loaded child
retain[id] = true;
found = true;
// loop through parents; retain the topmost loaded one if found
while (tile && tile.coord.z - 1 > coord.z) {
var parentId = tile.coord.parent(this.maxzoom).id;
tile = this._tiles[parentId];
if (tile && tile.loaded) {
delete retain[id];
retain[parentId] = true;
}
}
}
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
*
* @param {Coordinate} coord
* @param {number} minCoveringZoom
* @param {boolean} retain
* @returns {Tile} tile object
* @private
*/
findLoadedParent: function(coord, minCoveringZoom, retain) {
for (var z = coord.z - 1; z >= minCoveringZoom; z--) {
coord = coord.parent(this.maxzoom);
var tile = this._tiles[coord.id];
if (tile && tile.loaded) {
retain[coord.id] = true;
return tile;
}
if (this._cache.has(coord.id)) {
this.addTile(coord);
retain[coord.id] = true;
return this._tiles[coord.id];
}
}
},
/**
* Resizes the tile cache based on the current viewport's size.
*
* 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.
*
* @private
*/
updateCacheSize: function(transform) {
var widthInTiles = Math.ceil(transform.width / transform.tileSize) + 1;
var heightInTiles = Math.ceil(transform.height / transform.tileSize) + 1;
var approxTilesInView = widthInTiles * heightInTiles;
var commonZoomRange = 5;
this._cache.setMaxSize(Math.floor(approxTilesInView * commonZoomRange));
},
/**
* Removes tiles that are outside the viewport and adds new tiles that
* are inside the viewport.
* @private
*/
update: function(transform, fadeDuration) {
var i;
var coord;
var tile;
this.updateCacheSize(transform);
// Determine the overzooming/underzooming amounts.
var zoom = (this.roundZoom ? Math.round : Math.floor)(this.getZoom(transform));
var minCoveringZoom = Math.max(zoom - TilePyramid.maxOverzooming, this.minzoom);
var maxCoveringZoom = Math.max(zoom + TilePyramid.maxUnderzooming, this.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.
var retain = {};
var now = new Date().getTime();
// Covered is a list of retained tiles who's areas are full covered by other,
// better, retained tiles. They are not drawn separately.
this._coveredTiles = {};
var required = this.used ? transform.coveringTiles(this) : [];
for (i = 0; i < required.length; i++) {
coord = required[i];
tile = this.addTile(coord);
retain[coord.id] = true;
if (tile.loaded)
continue;
// The tile we require is not yet loaded.
// Retain child or parent tiles that cover the same area.
if (!this.findLoadedChildren(coord, maxCoveringZoom, retain)) {
this.findLoadedParent(coord, minCoveringZoom, retain);
}
}
var parentsForFading = {};
var ids = Object.keys(retain);
for (var k = 0; k < ids.length; k++) {
var id = ids[k];
coord = TileCoord.fromID(id);
tile = this._tiles[id];
if (tile && tile.timeAdded > now - (fadeDuration || 0)) {
// This tile is still fading in. Find tiles to cross-fade with it.
if (this.findLoadedChildren(coord, maxCoveringZoom, retain)) {
retain[id] = true;
}
this.findLoadedParent(coord, minCoveringZoom, parentsForFading);
}
}
var 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] = true;
}
// Remove the tiles we don't need anymore.
var remove = util.keysDifference(this._tiles, retain);
for (i = 0; i < remove.length; i++) {
this.removeTile(+remove[i]);
}
this.transform = transform;
},
/**
* Add a tile, given its coordinate, to the pyramid.
* @param {Coordinate} coord
* @returns {Coordinate} the coordinate.
* @private
*/
addTile: function(coord) {
var tile = this._tiles[coord.id];
if (tile)
return tile;
var wrapped = coord.wrapped();
tile = this._tiles[wrapped.id];
if (!tile) {
tile = this._cache.get(wrapped.id);
if (tile && this._redoPlacement) {
this._redoPlacement(tile);
}
}
if (!tile) {
var zoom = coord.z;
var overscaling = zoom > this.maxzoom ? Math.pow(2, zoom - this.maxzoom) : 1;
tile = new Tile(wrapped, this.tileSize * overscaling, this.maxzoom);
this._load(tile, this._tileLoaded.bind(this, tile));
}
tile.uses++;
this._tiles[coord.id] = tile;
this.fire('tile.add', {tile: tile});
return tile;
},
/**
* Remove a tile, given its id, from the pyramid
* @param {string|number} id tile id
* @returns {undefined} nothing
* @private
*/
removeTile: function(id) {
var tile = this._tiles[id];
if (!tile)
return;
tile.uses--;
delete this._tiles[id];
this.fire('tile.remove', {tile: tile});
if (tile.uses > 0)
return;
if (tile.loaded) {
this._cache.add(tile.coord.wrapped().id, tile);
} else {
tile.aborted = true;
this._abort(tile);
this._unload(tile);
}
},
/**
* Remove all tiles from this pyramid
* @private
*/
clearTiles: function() {
for (var 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 {Array<Coordinate>} 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.
* @private
*/
tilesIn: function(queryGeometry) {
var tileResults = {};
var ids = this.orderedIDs();
var minX = Infinity;
var minY = Infinity;
var maxX = -Infinity;
var maxY = -Infinity;
var z = queryGeometry[0].zoom;
for (var k = 0; k < queryGeometry.length; k++) {
var 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 (var i = 0; i < ids.length; i++) {
var tile = this._tiles[ids[i]];
var coord = TileCoord.fromID(ids[i]);
var tileSpaceBounds = [
coordinateToTilePoint(coord, tile.sourceMaxZoom, new Coordinate(minX, minY, z)),
coordinateToTilePoint(coord, tile.sourceMaxZoom, new Coordinate(maxX, maxY, z))
];
if (tileSpaceBounds[0].x < EXTENT && tileSpaceBounds[0].y < EXTENT &&
tileSpaceBounds[1].x >= 0 && tileSpaceBounds[1].y >= 0) {
var tileSpaceQueryGeometry = [];
for (var j = 0; j < queryGeometry.length; j++) {
tileSpaceQueryGeometry.push(coordinateToTilePoint(coord, tile.sourceMaxZoom, queryGeometry[j]));
}
var tileResult = tileResults[tile.coord.id];
if (tileResult === undefined) {
tileResult = tileResults[tile.coord.id] = {
tile: tile,
coord: coord,
queryGeometry: [],
scale: Math.pow(2, this.transform.zoom - tile.coord.z)
};
}
// Wrapped tiles share one tileResult object but can have multiple queryGeometry parts
tileResult.queryGeometry.push(tileSpaceQueryGeometry);
}
}
var results = [];
for (var t in tileResults) {
results.push(tileResults[t]);
}
return results;
},
redoPlacement: function () {
var ids = this.orderedIDs();
for (var i = 0; i < ids.length; i++) {
var tile = this.getTileByID(ids[i]);
tile.redoPlacement(this);
}
},
getVisibleCoordinates: function () {
return this.renderedIDs().map(TileCoord.fromID);
}
});
/**
* Convert a coordinate to a point in a tile's coordinate space.
* @param {Coordinate} tileCoord
* @param {Coordinate} coord
* @returns {Object} position
* @private
*/
function coordinateToTilePoint(tileCoord, sourceMaxZoom, coord) {
var zoomedCoord = coord.zoomTo(Math.min(tileCoord.z, sourceMaxZoom));
return {
x: (zoomedCoord.column - (tileCoord.x + tileCoord.w * Math.pow(2, tileCoord.z))) * EXTENT,
y: (zoomedCoord.row - tileCoord.y) * EXTENT
};
}
function compareKeyZoom(a, b) {
return (a % 32) - (b % 32);
}