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/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
* full list of contributors). Published under the 2-clause BSD license.
* See license.txt in the OpenLayers distribution or repository for the
* full text of the license. */
/**
* @requires OpenLayers/Util.js
* @requires OpenLayers/BaseTypes.js
* @requires OpenLayers/BaseTypes/Element.js
* @requires OpenLayers/Layer/Grid.js
* @requires OpenLayers/Tile/Image.js
*/
/**
* Class: OpenLayers.TileManager
* Provides queueing of image requests and caching of image elements.
*
* Queueing avoids unnecessary image requests while changing zoom levels
* quickly, and helps improve dragging performance on mobile devices that show
* a lag in dragging when loading of new images starts. <zoomDelay> and
* <moveDelay> are the configuration options to control this behavior.
*
* Caching avoids setting the src on image elements for images that have already
* been used. Several maps can share a TileManager instance, in which case each
* map gets its own tile queue, but all maps share the same tile cache.
*/
OpenLayers.TileManager = OpenLayers.Class({
/**
* APIProperty: cacheSize
* {Number} Number of image elements to keep referenced in this instance's
* cache for fast reuse. Default is 256.
*/
cacheSize: 256,
/**
* APIProperty: tilesPerFrame
* {Number} Number of queued tiles to load per frame (see <frameDelay>).
* Default is 2.
*/
tilesPerFrame: 2,
/**
* APIProperty: frameDelay
* {Number} Delay between tile loading frames (see <tilesPerFrame>) in
* milliseconds. Default is 16.
*/
frameDelay: 16,
/**
* APIProperty: moveDelay
* {Number} Delay in milliseconds after a map's move event before loading
* tiles. Default is 100.
*/
moveDelay: 100,
/**
* APIProperty: zoomDelay
* {Number} Delay in milliseconds after a map's zoomend event before loading
* tiles. Default is 200.
*/
zoomDelay: 200,
/**
* Property: maps
* {Array(<OpenLayers.Map>)} The maps to manage tiles on.
*/
maps: null,
/**
* Property: tileQueueId
* {Object} The ids of the <drawTilesFromQueue> loop, keyed by map id.
*/
tileQueueId: null,
/**
* Property: tileQueue
* {Object(Array(<OpenLayers.Tile>))} Tiles queued for drawing, keyed by
* map id.
*/
tileQueue: null,
/**
* Property: tileCache
* {Object} Cached image elements, keyed by URL.
*/
tileCache: null,
/**
* Property: tileCacheIndex
* {Array(String)} URLs of cached tiles. First entry is the least recently
* used.
*/
tileCacheIndex: null,
/**
* Constructor: OpenLayers.TileManager
* Constructor for a new <OpenLayers.TileManager> instance.
*
* Parameters:
* options - {Object} Configuration for this instance.
*/
initialize: function(options) {
OpenLayers.Util.extend(this, options);
this.maps = [];
this.tileQueueId = {};
this.tileQueue = {};
this.tileCache = {};
this.tileCacheIndex = [];
},
/**
* Method: addMap
* Binds this instance to a map
*
* Parameters:
* map - {<OpenLayers.Map>}
*/
addMap: function(map) {
if (this._destroyed || !OpenLayers.Layer.Grid) {
return;
}
this.maps.push(map);
this.tileQueue[map.id] = [];
for (var i=0, ii=map.layers.length; i<ii; ++i) {
this.addLayer({layer: map.layers[i]});
}
map.events.on({
move: this.move,
zoomend: this.zoomEnd,
changelayer: this.changeLayer,
addlayer: this.addLayer,
preremovelayer: this.removeLayer,
scope: this
});
},
/**
* Method: removeMap
* Unbinds this instance from a map
*
* Parameters:
* map - {<OpenLayers.Map>}
*/
removeMap: function(map) {
if (this._destroyed || !OpenLayers.Layer.Grid) {
return;
}
window.clearTimeout(this.tileQueueId[map.id]);
if (map.layers) {
for (var i=0, ii=map.layers.length; i<ii; ++i) {
this.removeLayer({layer: map.layers[i]});
}
}
if (map.events) {
map.events.un({
move: this.move,
zoomend: this.zoomEnd,
changelayer: this.changeLayer,
addlayer: this.addLayer,
preremovelayer: this.removeLayer,
scope: this
});
}
delete this.tileQueue[map.id];
delete this.tileQueueId[map.id];
OpenLayers.Util.removeItem(this.maps, map);
},
/**
* Method: move
* Handles the map's move event
*
* Parameters:
* evt - {Object} Listener argument
*/
move: function(evt) {
this.updateTimeout(evt.object, this.moveDelay, true);
},
/**
* Method: zoomEnd
* Handles the map's zoomEnd event
*
* Parameters:
* evt - {Object} Listener argument
*/
zoomEnd: function(evt) {
this.updateTimeout(evt.object, this.zoomDelay);
},
/**
* Method: changeLayer
* Handles the map's changeLayer event
*
* Parameters:
* evt - {Object} Listener argument
*/
changeLayer: function(evt) {
if (evt.property === 'visibility' || evt.property === 'params') {
this.updateTimeout(evt.object, 0);
}
},
/**
* Method: addLayer
* Handles the map's addlayer event
*
* Parameters:
* evt - {Object} The listener argument
*/
addLayer: function(evt) {
var layer = evt.layer;
if (layer instanceof OpenLayers.Layer.Grid) {
layer.events.on({
addtile: this.addTile,
retile: this.clearTileQueue,
scope: this
});
var i, j, tile;
for (i=layer.grid.length-1; i>=0; --i) {
for (j=layer.grid[i].length-1; j>=0; --j) {
tile = layer.grid[i][j];
this.addTile({tile: tile});
if (tile.url && !tile.imgDiv) {
this.manageTileCache({object: tile});
}
}
}
}
},
/**
* Method: removeLayer
* Handles the map's preremovelayer event
*
* Parameters:
* evt - {Object} The listener argument
*/
removeLayer: function(evt) {
var layer = evt.layer;
if (layer instanceof OpenLayers.Layer.Grid) {
this.clearTileQueue({object: layer});
if (layer.events) {
layer.events.un({
addtile: this.addTile,
retile: this.clearTileQueue,
scope: this
});
}
if (layer.grid) {
var i, j, tile;
for (i=layer.grid.length-1; i>=0; --i) {
for (j=layer.grid[i].length-1; j>=0; --j) {
tile = layer.grid[i][j];
this.unloadTile({object: tile});
}
}
}
}
},
/**
* Method: updateTimeout
* Applies the <moveDelay> or <zoomDelay> to the <drawTilesFromQueue> loop,
* and schedules more queue processing after <frameDelay> if there are still
* tiles in the queue.
*
* Parameters:
* map - {<OpenLayers.Map>} The map to update the timeout for
* delay - {Number} The delay to apply
* nice - {Boolean} If true, the timeout function will only be created if
* the tilequeue is not empty. This is used by the move handler to
* avoid impacts on dragging performance. For other events, the tile
* queue may not be populated yet, so we need to set the timer
* regardless of the queue size.
*/
updateTimeout: function(map, delay, nice) {
window.clearTimeout(this.tileQueueId[map.id]);
var tileQueue = this.tileQueue[map.id];
if (!nice || tileQueue.length) {
this.tileQueueId[map.id] = window.setTimeout(
OpenLayers.Function.bind(function() {
this.drawTilesFromQueue(map);
if (tileQueue.length) {
this.updateTimeout(map, this.frameDelay);
}
}, this), delay
);
}
},
/**
* Method: addTile
* Listener for the layer's addtile event
*
* Parameters:
* evt - {Object} The listener argument
*/
addTile: function(evt) {
if (evt.tile instanceof OpenLayers.Tile.Image) {
evt.tile.events.on({
beforedraw: this.queueTileDraw,
beforeload: this.manageTileCache,
loadend: this.addToCache,
unload: this.unloadTile,
scope: this
});
} else {
// Layer has the wrong tile type, so don't handle it any longer
this.removeLayer({layer: evt.tile.layer});
}
},
/**
* Method: unloadTile
* Listener for the tile's unload event
*
* Parameters:
* evt - {Object} The listener argument
*/
unloadTile: function(evt) {
var tile = evt.object;
tile.events.un({
beforedraw: this.queueTileDraw,
beforeload: this.manageTileCache,
loadend: this.addToCache,
unload: this.unloadTile,
scope: this
});
OpenLayers.Util.removeItem(this.tileQueue[tile.layer.map.id], tile);
},
/**
* Method: queueTileDraw
* Adds a tile to the queue that will draw it.
*
* Parameters:
* evt - {Object} Listener argument of the tile's beforedraw event
*/
queueTileDraw: function(evt) {
var tile = evt.object;
var queued = false;
var layer = tile.layer;
var url = layer.getURL(tile.bounds);
var img = this.tileCache[url];
if (img && img.className !== 'olTileImage') {
// cached image no longer valid, e.g. because we're olTileReplacing
delete this.tileCache[url];
OpenLayers.Util.removeItem(this.tileCacheIndex, url);
img = null;
}
// queue only if image with same url not cached already
if (layer.url && (layer.async || !img)) {
// add to queue only if not in queue already
var tileQueue = this.tileQueue[layer.map.id];
if (!~OpenLayers.Util.indexOf(tileQueue, tile)) {
tileQueue.push(tile);
}
queued = true;
}
return !queued;
},
/**
* Method: drawTilesFromQueue
* Draws tiles from the tileQueue, and unqueues the tiles
*/
drawTilesFromQueue: function(map) {
var tileQueue = this.tileQueue[map.id];
var limit = this.tilesPerFrame;
var animating = map.zoomTween && map.zoomTween.playing;
while (!animating && tileQueue.length && limit) {
tileQueue.shift().draw(true);
--limit;
}
},
/**
* Method: manageTileCache
* Adds, updates, removes and fetches cache entries.
*
* Parameters:
* evt - {Object} Listener argument of the tile's beforeload event
*/
manageTileCache: function(evt) {
var tile = evt.object;
var img = this.tileCache[tile.url];
if (img) {
// if image is on its layer's backbuffer, remove it from backbuffer
if (img.parentNode &&
OpenLayers.Element.hasClass(img.parentNode, 'olBackBuffer')) {
img.parentNode.removeChild(img);
img.id = null;
}
// only use image from cache if it is not on a layer already
if (!img.parentNode) {
img.style.visibility = 'hidden';
img.style.opacity = 0;
tile.setImage(img);
// LRU - move tile to the end of the array to mark it as the most
// recently used
OpenLayers.Util.removeItem(this.tileCacheIndex, tile.url);
this.tileCacheIndex.push(tile.url);
}
}
},
/**
* Method: addToCache
*
* Parameters:
* evt - {Object} Listener argument for the tile's loadend event
*/
addToCache: function(evt) {
var tile = evt.object;
if (!this.tileCache[tile.url]) {
if (!OpenLayers.Element.hasClass(tile.imgDiv, 'olImageLoadError')) {
if (this.tileCacheIndex.length >= this.cacheSize) {
delete this.tileCache[this.tileCacheIndex[0]];
this.tileCacheIndex.shift();
}
this.tileCache[tile.url] = tile.imgDiv;
this.tileCacheIndex.push(tile.url);
}
}
},
/**
* Method: clearTileQueue
* Clears the tile queue from tiles of a specific layer
*
* Parameters:
* evt - {Object} Listener argument of the layer's retile event
*/
clearTileQueue: function(evt) {
var layer = evt.object;
var tileQueue = this.tileQueue[layer.map.id];
for (var i=tileQueue.length-1; i>=0; --i) {
if (tileQueue[i].layer === layer) {
tileQueue.splice(i, 1);
}
}
},
/**
* Method: destroy
*/
destroy: function() {
for (var i=this.maps.length-1; i>=0; --i) {
this.removeMap(this.maps[i]);
}
this.maps = null;
this.tileQueue = null;
this.tileQueueId = null;
this.tileCache = null;
this.tileCacheIndex = null;
this._destroyed = true;
}
});