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Diffstat (limited to 'misc/openlayers/lib/OpenLayers/Tile/UTFGrid.js')
| -rw-r--r-- | misc/openlayers/lib/OpenLayers/Tile/UTFGrid.js | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/misc/openlayers/lib/OpenLayers/Tile/UTFGrid.js b/misc/openlayers/lib/OpenLayers/Tile/UTFGrid.js new file mode 100644 index 0000000..2836ee0 --- /dev/null +++ b/misc/openlayers/lib/OpenLayers/Tile/UTFGrid.js @@ -0,0 +1,252 @@ +/* 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/Tile.js + * @requires OpenLayers/Format/JSON.js + * @requires OpenLayers/Request.js + */ + +/** + * Class: OpenLayers.Tile.UTFGrid + * Instances of OpenLayers.Tile.UTFGrid are used to manage + * UTFGrids. This is an unusual tile type in that it doesn't have a + * rendered image; only a 'hit grid' that can be used to + * look up feature attributes. + * + * See the <OpenLayers.Tile.UTFGrid> constructor for details on constructing a + * new instance. + * + * Inherits from: + * - <OpenLayers.Tile> + */ +OpenLayers.Tile.UTFGrid = OpenLayers.Class(OpenLayers.Tile, { + + /** + * Property: url + * {String} + * The URL of the UTFGrid file being requested. Provided by the <getURL> + * method. + */ + url: null, + + /** + * Property: utfgridResolution + * {Number} + * Ratio of the pixel width to the width of a UTFGrid data point. If an + * entry in the grid represents a 4x4 block of pixels, the + * utfgridResolution would be 4. Default is 2. + */ + utfgridResolution: 2, + + /** + * Property: json + * {Object} + * Stores the parsed JSON tile data structure. + */ + json: null, + + /** + * Property: format + * {OpenLayers.Format.JSON} + * Parser instance used to parse JSON for cross browser support. The native + * JSON.parse method will be used where available (all except IE<8). + */ + format: null, + + /** + * Constructor: OpenLayers.Tile.UTFGrid + * Constructor for a new <OpenLayers.Tile.UTFGrid> instance. + * + * Parameters: + * layer - {<OpenLayers.Layer>} layer that the tile will go in. + * position - {<OpenLayers.Pixel>} + * bounds - {<OpenLayers.Bounds>} + * url - {<String>} Deprecated. Remove me in 3.0. + * size - {<OpenLayers.Size>} + * options - {Object} + */ + + /** + * APIMethod: destroy + * Clean up. + */ + destroy: function() { + this.clear(); + OpenLayers.Tile.prototype.destroy.apply(this, arguments); + }, + + /** + * Method: draw + * Check that a tile should be drawn, and draw it. + * In the case of UTFGrids, "drawing" it means fetching and + * parsing the json. + * + * Returns: + * {Boolean} Was a tile drawn? + */ + draw: function() { + var drawn = OpenLayers.Tile.prototype.draw.apply(this, arguments); + if (drawn) { + if (this.isLoading) { + this.abortLoading(); + //if we're already loading, send 'reload' instead of 'loadstart'. + this.events.triggerEvent("reload"); + } else { + this.isLoading = true; + this.events.triggerEvent("loadstart"); + } + this.url = this.layer.getURL(this.bounds); + + if (this.layer.useJSONP) { + // Use JSONP method to avoid xbrowser policy + var ols = new OpenLayers.Protocol.Script({ + url: this.url, + callback: function(response) { + this.isLoading = false; + this.events.triggerEvent("loadend"); + this.json = response.data; + }, + scope: this + }); + ols.read(); + this.request = ols; + } else { + // Use standard XHR + this.request = OpenLayers.Request.GET({ + url: this.url, + callback: function(response) { + this.isLoading = false; + this.events.triggerEvent("loadend"); + if (response.status === 200) { + this.parseData(response.responseText); + } + }, + scope: this + }); + } + } else { + this.unload(); + } + return drawn; + }, + + /** + * Method: abortLoading + * Cancel a pending request. + */ + abortLoading: function() { + if (this.request) { + this.request.abort(); + delete this.request; + } + this.isLoading = false; + }, + + /** + * Method: getFeatureInfo + * Get feature information associated with a pixel offset. If the pixel + * offset corresponds to a feature, the returned object will have id + * and data properties. Otherwise, null will be returned. + * + * + * Parameters: + * i - {Number} X-axis pixel offset (from top left of tile) + * j - {Number} Y-axis pixel offset (from top left of tile) + * + * Returns: + * {Object} Object with feature id and data properties corresponding to the + * given pixel offset. + */ + getFeatureInfo: function(i, j) { + var info = null; + if (this.json) { + var id = this.getFeatureId(i, j); + if (id !== null) { + info = {id: id, data: this.json.data[id]}; + } + } + return info; + }, + + /** + * Method: getFeatureId + * Get the identifier for the feature associated with a pixel offset. + * + * Parameters: + * i - {Number} X-axis pixel offset (from top left of tile) + * j - {Number} Y-axis pixel offset (from top left of tile) + * + * Returns: + * {Object} The feature identifier corresponding to the given pixel offset. + * Returns null if pixel doesn't correspond to a feature. + */ + getFeatureId: function(i, j) { + var id = null; + if (this.json) { + var resolution = this.utfgridResolution; + var row = Math.floor(j / resolution); + var col = Math.floor(i / resolution); + var charCode = this.json.grid[row].charCodeAt(col); + var index = this.indexFromCharCode(charCode); + var keys = this.json.keys; + if (!isNaN(index) && (index in keys)) { + id = keys[index]; + } + } + return id; + }, + + /** + * Method: indexFromCharCode + * Given a character code for one of the UTFGrid "grid" characters, + * resolve the integer index for the feature id in the UTFGrid "keys" + * array. + * + * Parameters: + * charCode - {Integer} + * + * Returns: + * {Integer} Index for the feature id from the keys array. + */ + indexFromCharCode: function(charCode) { + if (charCode >= 93) { + charCode--; + } + if (charCode >= 35) { + charCode --; + } + return charCode - 32; + }, + + /** + * Method: parseData + * Parse the JSON from a request + * + * Parameters: + * str - {String} UTFGrid as a JSON string. + * + * Returns: + * {Object} parsed javascript data + */ + parseData: function(str) { + if (!this.format) { + this.format = new OpenLayers.Format.JSON(); + } + this.json = this.format.read(str); + }, + + /** + * Method: clear + * Delete data stored with this tile. + */ + clear: function() { + this.json = null; + }, + + CLASS_NAME: "OpenLayers.Tile.UTFGrid" + +}); |