/* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for
* full list of contributors). Published under the Clear BSD license.
* See http://svn.openlayers.org/trunk/openlayers/license.txt for the
* full text of the license. */
/*
* @requires OpenLayers/Util.js
* @requires OpenLayers/Console.js
*/
/*
* Class: OpenLayers.Tile
* This is a class designed to designate a single tile, however
* it is explicitly designed to do relatively little. Tiles store
* information about themselves -- such as the URL that they are related
* to, and their size - but do not add themselves to the layer div
* automatically, for example. Create a new tile with the
* <OpenLayers.Tile> constructor, or a subclass.
*
* TBD 3.0 - remove reference to url in above paragraph
*
*/
OpenLayers.Tile = OpenLayers.Class({
/**
* Constant: EVENT_TYPES
* {Array(String)} Supported application event types
*/
EVENT_TYPES: [ "loadstart", "loadend", "reload", "unload"],
/**
* APIProperty: events
* {<OpenLayers.Events>} An events object that handles all
* events on the tile.
*/
events: null,
/**
* Property: id
* {String} null
*/
id: null,
/**
* Property: layer
* {<OpenLayers.Layer>} layer the tile is attached to
*/
layer: null,
/**
* Property: url
* {String} url of the request.
*
* TBD 3.0
* Deprecated. The base tile class does not need an url. This should be
* handled in subclasses. Does not belong here.
*/
url: null,
/**
* APIProperty: bounds
* {<OpenLayers.Bounds>} null
*/
bounds: null,
/**
* Property: size
* {<OpenLayers.Size>} null
*/
size: null,
/**
* Property: position
* {<OpenLayers.Pixel>} Top Left pixel of the tile
*/
position: null,
/**
* Property: isLoading
* {Boolean} Is the tile loading?
*/
isLoading: false,
/** TBD 3.0 -- remove 'url' from the list of parameters to the constructor.
* there is no need for the base tile class to have a url.
*
* Constructor: OpenLayers.Tile
* Constructor for a new <OpenLayers.Tile> instance.
*
* Parameters:
* layer - {<OpenLayers.Layer>} layer that the tile will go in.
* position - {<OpenLayers.Pixel>}
* bounds - {<OpenLayers.Bounds>}
* url - {<String>}
* size - {<OpenLayers.Size>}
*/
initialize: function(layer, position, bounds, url, size) {
this.layer = layer;
this.position = position.clone();
this.bounds = bounds.clone();
this.url = url;
this.size = size.clone();
//give the tile a unique id based on its BBOX.
this.id = OpenLayers.Util.createUniqueID("Tile_");
this.events = new OpenLayers.Events(this, null, this.EVENT_TYPES);
},
/**
* Method: unload
* Call immediately before destroying if you are listening to tile
* events, so that counters are properly handled if tile is still
* loading at destroy-time. Will only fire an event if the tile is
* still loading.
*/
unload: function() {
if (this.isLoading) {
this.isLoading = false;
this.events.triggerEvent("unload");
}
},
/**
* APIMethod: destroy
* Nullify references to prevent circular references and memory leaks.
*/
destroy:function() {
this.layer = null;
this.bounds = null;
this.size = null;
this.position = null;
this.events.destroy();
this.events = null;
},
/**
* Method: clone
*
* Parameters:
* obj - {<OpenLayers.Tile>} The tile to be cloned
*
* Returns:
* {<OpenLayers.Tile>} An exact clone of this <OpenLayers.Tile>
*/
clone: function (obj) {
if (obj == null) {
obj = new OpenLayers.Tile(this.layer,
this.position,
this.bounds,
this.url,
this.size);
}
// catch any randomly tagged-on properties
OpenLayers.Util.applyDefaults(obj, this);
return obj;
},
/**
* Method: draw
* Clear whatever is currently in the tile, then return whether or not
* it should actually be re-drawn.
*
* Returns:
* {Boolean} Whether or not the tile should actually be drawn. Note that
* this is not really the best way of doing things, but such is
* the way the code has been developed. Subclasses call this and
* depend on the return to know if they should draw or not.
*/
draw: function() {
var maxExtent = this.layer.maxExtent;
var withinMaxExtent = (maxExtent &&
this.bounds.intersectsBounds(maxExtent, false));
// The only case where we *wouldn't* want to draw the tile is if the
// tile is outside its layer's maxExtent.
this.shouldDraw = (withinMaxExtent || this.layer.displayOutsideMaxExtent);
//clear tile's contents and mark as not drawn
this.clear();
return this.shouldDraw;
},
/**
* Method: moveTo
* Reposition the tile.
*
* Parameters:
* bounds - {<OpenLayers.Bounds>}
* position - {<OpenLayers.Pixel>}
* redraw - {Boolean} Call draw method on tile after moving.
* Default is true
*/
moveTo: function (bounds, position, redraw) {
if (redraw == null) {
redraw = true;
}
this.bounds = bounds.clone();
this.position = position.clone();
if (redraw) {
this.draw();
}
},
/**
* Method: clear
* Clear the tile of any bounds/position-related data so that it can
* be reused in a new location. To be implemented by subclasses.
*/
clear: function() {
// to be implemented by subclasses
},
/**
* Method: getBoundsFromBaseLayer
* Take the pixel locations of the corner of the tile, and pass them to
* the base layer and ask for the location of those pixels, so that
* displaying tiles over Google works fine.
*
* Parameters:
* position - {<OpenLayers.Pixel>}
*
* Returns:
* bounds - {<OpenLayers.Bounds>}
*/
getBoundsFromBaseLayer: function(position) {
var msg = OpenLayers.i18n('reprojectDeprecated',
{'layerName':this.layer.name});
OpenLayers.Console.warn(msg);
var topLeft = this.layer.map.getLonLatFromLayerPx(position);
var bottomRightPx = position.clone();
bottomRightPx.x += this.size.w;
bottomRightPx.y += this.size.h;
var bottomRight = this.layer.map.getLonLatFromLayerPx(bottomRightPx);
// Handle the case where the base layer wraps around the date line.
// Google does this, and it breaks WMS servers to request bounds in
// that fashion.
if (topLeft.lon > bottomRight.lon) {
if (topLeft.lon < 0) {
topLeft.lon = -180 - (topLeft.lon+180);
} else {
bottomRight.lon = 180+bottomRight.lon+180;
}
}
var bounds = new OpenLayers.Bounds(topLeft.lon,
bottomRight.lat,
bottomRight.lon,
topLeft.lat);
return bounds;
},
/**
* Method: showTile
* Show the tile only if it should be drawn.
*/
showTile: function() {
if (this.shouldDraw) {
this.show();
}
},
/**
* Method: show
* Show the tile. To be implemented by subclasses.
*/
show: function() { },
/**
* Method: hide
* Hide the tile. To be implemented by subclasses.
*/
hide: function() { },
CLASS_NAME: "OpenLayers.Tile"
});