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// A source of tile images of a specific width/height, zoom level range, and some other attributes

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var Source = Class.create({

     3

    initialize: function (path, tile_width, tile_height, zoom_min, zoom_max) {

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        this.path = path;

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        this.tile_width = tile_width;

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        this.tile_height = tile_height;

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        this.zoom_min = zoom_min;

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        this.zoom_max = zoom_max;

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        this.refresh = false;

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        this.opt_key = this.opt_value = null;

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    },

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    // build a URL for the given tile image

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    build_url: function (col, row, zl, sw, sh) {

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        // two-bit hash (0-4) based on the (col, row)

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        var hash = ( (col % 2) << 1 | (row % 2) ) + 1;

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        // the subdomain to use

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        var subdomain = "";

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        if (0)

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            subdomain = "tile" + hash + ".";

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        // the (x, y) co-ordinates

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        var x = col * this.tile_width;

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        var y = row * this.tile_height;

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        var url = this.path + "?x=" + x + "&y=" + y + "&z=" + zl + "&sw=" + sw + "&sh=" + sh;

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        if (this.refresh)

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            url += "&ts=" + new Date().getTime();

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        if (this.opt_key && this.opt_value)

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            url += "&" + this.opt_key + "=" + this.opt_value;

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        return url;

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    },

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});

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// a viewport that contains a substrate which contains several zoom layers which contain many tiles

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var Viewport = Class.create({

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    initialize: function (source, viewport_id) {

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        this.source = source;

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        this.id = viewport_id;

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        this.div = $(viewport_id);

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        this.substrate = this.div.down("div.substrate");

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        // the stack of zoom levels

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        this.zoom_layers = [];

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        // pre-populate the stack

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        for (var zoom_level = source.zoom_min; zoom_level <= source.zoom_max; zoom_level++) {

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            var zoom_layer = new ZoomLayer(source, zoom_level);

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            this.substrate.appendChild(zoom_layer.div);

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            this.zoom_layers[zoom_level] = zoom_layer;

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        }

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        // make the substrate draggable

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        this.draggable = new Draggable(this.substrate, {

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            onStart: this.on_scroll_start.bind(this),

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            onDrag: this.on_scroll_move.bind(this),

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            onEnd: this.on_scroll_end.bind(this),

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        });

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        // event handlers

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        Event.observe(this.substrate, "dblclick", this.on_dblclick.bindAsEventListener(this));

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        Event.observe(this.substrate, "mousewheel", this.on_mousewheel.bindAsEventListener(this));

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        Event.observe(this.substrate, "DOMMouseScroll", this.on_mousewheel.bindAsEventListener(this));     // mozilla

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        Event.observe(document, "resize", this.on_resize.bindAsEventListener(this));

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        // load initial view

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        this.update_size();

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        // this sets the scroll offsets, zoom level, and loads the tiles

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        this.zoom_to(0, 0, 0);

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    },

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    /* event handlers */

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    // window resized

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    on_resize: function (ev) {

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        this.update_size();

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        this.update_tiles();

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    },

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    // double-click handler

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    on_dblclick: function (ev) {

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        var offset = this.event_offset(ev);

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        this.zoom_center_to(

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            this.scroll_x + offset.x,

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            this.scroll_y + offset.y,

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            1   // zoom in

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        );

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    },

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    // mousewheel handler

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    on_mousewheel: function (ev) {

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        // this works in very weird ways, so it's based on code from http://adomas.org/javascript-mouse-wheel/

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        // (it didn't include any license, so this is written out manually)

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        var delta;

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        // this is browser-dependant...

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        if (ev.wheelDelta) {

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            // IE + Opera

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            delta = ev.wheelDelta;

   110

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            if (window.opera) {  

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                // Opera, but apparently not newer versions?

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                //delta = -delta;

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            }

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        } else if (ev.detail) {

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            // Mozilla

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            delta = -ev.detail;

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        } else {

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            // mousewheel not supported...

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            return;

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        }

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        // don't scroll the page

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        if (ev.preventDefault)

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            ev.preventDefault();

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        // delta > 0 : scroll up, zoom in

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        // delta < 0 : scroll down, zoom out

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        delta = delta < 0 ? -1 : 1;

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        // Firefox's DOMMouseEvent's pageX/Y attributes are broken. layerN is for mozilla, offsetN for IE, seems to work

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        // absolute location of the cursor

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        var x = parseInt(ev.target.style.left) + (ev.layerX ? ev.layerX : ev.offsetX);

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        var y = parseInt(ev.target.style.top) + (ev.layerY ? ev.layerY : ev.offsetY);

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        // zoom \o/

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        this.zoom_center_to(x, y, delta);

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    },

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    // substrate scroll was started

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    on_scroll_start: function (ev) {

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    },

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    // substrate was scrolled, update scroll_{x,y}, and then update tiles after 100ms

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    on_scroll_move: function (ev) {

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        this.update_scroll();

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        this.update_after_timeout();

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    },

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    // substrate scroll was ended, update tiles now

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    on_scroll_end: function (ev) {

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        this.update_now();

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    },

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    /* get state */

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    // return the absolute (x, y) coords of the given event inside the viewport

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    event_offset: function (ev) {

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        var offset = this.div.cumulativeOffset();

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        return {

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            x: ev.pointerX() - offset.left, 

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            y: ev.pointerY() - offset.top

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        };

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    },

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    /* modify state */

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    // scroll the view to place the given absolute (x, y) co-ordinate at the top left

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    scroll_to: function (x, y) {

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        // update it via the style

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        this.substrate.style.top = "-" + y + "px";

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        this.substrate.style.left = "-" + x + "px";

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        // update these as well

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        this.scroll_x = x;

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        this.scroll_y = y;

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    },

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    // scroll the view to place the given absolute (x, y) co-ordinate at the center

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    scroll_center_to: function (x, y) {

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        return this.scroll_to(

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            x - this.center_offset_x,

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            y - this.center_offset_y

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        );

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    },

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    // zoom à la delta such that the given (zoomed) absolute (x, y) co-ordinates will be at the top left

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    zoom_scaled: function (x, y, delta) {

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        if (!this.update_zoom(delta))

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            return false;

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        // scroll to the new position

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        this.scroll_to(x, y);

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        // update view

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        // XXX: ...

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        this.update_after_timeout();

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        return true;

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    },

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    // zoom à la delta such that the given (current) absolute (x, y) co-ordinates will be at the top left

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    zoom_to: function (x, y, delta) {

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        return this.zoom_scaled(

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            scaleByZoomDelta(x, delta),

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            scaleByZoomDelta(y, delta),

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            delta

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        );

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    },

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    // zoom à la delta such that the given (current) absolute (x, y) co-ordinates will be at the center

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    zoom_center_to: function (x, y, delta) {

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        return this.zoom_scaled(

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            scaleByZoomDelta(x, delta) - this.center_offset_x,

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            scaleByZoomDelta(y, delta) - this.center_offset_y,

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            delta

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        );

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    },

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    /* update view/state to reflect reality */

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    // figure out the viewport dimensions

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    update_size: function () {

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        this.view_width = this.div.getWidth();

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        this.view_height = this.div.getHeight();

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        this.center_offset_x = Math.floor(this.view_width / 2);

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        this.center_offset_y = Math.floor(this.view_height / 2);

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    },

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    // figure out the scroll offset as absolute pixel co-ordinates at the top left

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    update_scroll: function() {

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        this.scroll_x = -parseInt(this.substrate.style.left);

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        this.scroll_y = -parseInt(this.substrate.style.top);

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    },

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    // wiggle the ZoomLevels around to match the current zoom level

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    update_zoom: function(delta) {

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        if (!this.zoom_layer) {

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            // first zoom operation

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            // is the new zoom level valid?

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            if (!this.zoom_layers[delta])

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                return false;

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            // set the zoom layyer

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            this.zoom_layer = this.zoom_layers[delta];

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            // enable it

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            this.zoom_layer.enable(11);

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            // no need to .update_tiles or anything like that

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        } else {

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            // is the new zoom level valid?

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            if (!this.zoom_layers[this.zoom_layer.level + delta])

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                return false;

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            var zoom_old = this.zoom_layer;

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            var zoom_new = this.zoom_layers[this.zoom_layer.level + delta];

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            // XXX: ugly hack

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            if (this.zoom_timer) {

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                clearTimeout(this.zoom_timer);

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                this.zoom_timer = null;

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            }

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            // get other zoom layers out of the way

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            this.zoom_layers.each(function (zl) {

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                zl.disable();

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            });

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            // update the zoom layer

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            this.zoom_layer = zoom_new;

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            // apply new z-indexes, preferr the current one over the new one

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            zoom_new.enable(11);

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            zoom_old.enable(10);

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            // resize the tiles in the two zoom layers

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            zoom_new.update_tiles(zoom_new.level);

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            zoom_old.update_tiles(zoom_old.level);

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            // XXX: ugly hack

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            this.zoom_timer = setTimeout(function () { zoom_old.disable()}, 1000);

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        }

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        return true;

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    },

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    // ensure that all tiles that are currently visible are loaded

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    update_tiles: function() {

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        // short names for some vars...

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        var x = this.scroll_x;

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        var y = this.scroll_y;

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        var sw = this.view_width;

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        var sh = this.view_height;

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        var tw = this.source.tile_width;

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        var th = this.source.tile_height;

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        var zl = this.zoom_layer.level;

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        // figure out what set of columns are visible

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        var start_col = Math.max(0, Math.floor(x / tw));

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        var start_row = Math.max(0, Math.floor(y / th));

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        var end_col = Math.floor((x + sw) / tw);

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        var end_row = Math.floor((y + sh) / th);

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        // loop through all those tiles

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        for (var col = start_col; col <= end_col; col++) {

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            for (var row = start_row; row <= end_row; row++) {

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                // the tile's id

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                var id = "tile_" + this.zoom_layer.level + "_" + col + "_" + row;

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                // does the element exist already?

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                var t = $(id);

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                if (!t) {

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                    // build a new tile

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                    t = Builder.node("img", {

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                            src:    this.source.build_url(col, row, zl, sw, sh),

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                            id:     id,

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                            title:  "(" + col + ", " + row + ")",

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                            // style set later

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                        }

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                    );

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                    // set the CSS style stuff

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                    t.style.top = th * row;

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                    t.style.left = tw * col;

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                    t.style.display = "none";

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                    // wait for it to load

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                    Event.observe(t, "load", _tile_loaded.bindAsEventListener(t));

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                    // store the col/row

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                    t.__col = col;

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                    t.__row = row;

   345

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                    // add it to the zoom layer

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                    this.zoom_layer.add_tile(t);

   348

   349

                } else if (this.source.reload) {

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                    // force the tile to reload

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                    touch_tile(t, col, row);

   352

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                }

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            }

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        }

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/* XXX: fixme

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        // update the link-to-this-page thing

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        document.location.hash = "#goto_" + (x + g_w_half) + ":" + g_w + "_" + (y + g_h_half) + ":" + g_h + "_" + g_z;

   360

*/

   361

   362

    }, 

   363

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    // do update_tiles after 100ms, unless we are called again

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    update_after_timeout: function () {

   366

        this._update_idle = false;

   367

   368

        if (this._update_timeout)

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            clearTimeout(this._update_timeout);

   370

   371

        this._update_timeout = setTimeout(this._update_timeout_trigger.bind(this), 100);  

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    },

   373

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    _update_timeout_trigger: function () {

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        this._update_idle = true;

   376

   377

        this.update_tiles();

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    },

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    // call update_tiles if it hasn't been called due to update_after_timeout

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    update_now: function () {

   382

        if (this._update_timeout)

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            clearTimeout(this._update_timeout);

   384

   385

        if (!this._update_idle)

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            this.update_tiles();

   387

    },

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});

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// used by Viewport.update_tiles to make a tile visible after it has loaded

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function _tile_loaded (ev) {

   393

    this.style.display = "block";

   394

}

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// a zoom layer containing the tiles for one zoom level

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var ZoomLayer = Class.create({

   398

    initialize: function (source, zoom_level) {

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        this.source = source;

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        this.level = zoom_level;

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        this.div = Builder.node("div", { id: "zl_" + this.level, style: "position: relative; display: none;"});

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        // our tiles

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        this.tiles = [];

   405

    },

   406

   407

    // add a tile to this zoom layer

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    add_tile: function (tile) {

   409

        this.div.appendChild(tile);

   410

        this.tiles.push(tile);

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    },

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    // make this zoom layer visible with the given z-index

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    enable: function (z_index) {

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        this.div.style.zIndex = z_index;

   416

        this.div.show();

   417

    },

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    // hide this zoom layer

   420

    disable: function (z_index) {

   421

        this.div.hide();

   422

    },

   423

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    // update the tiles in this zoom layer so that they are in the correct position and of the correct size when

   425

    // viewed with the given zoom level

   426

    update_tiles: function (zoom_level) {

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        var zd = zoom_level - this.level;

   428

   429

        var tw = scaleByZoomDelta(this.source.tile_width, zd);

   430

        var th = scaleByZoomDelta(this.source.tile_height, zd);

   431

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        var tiles = this.tiles;

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        var tiles_len = tiles.length;

   434

        var t, ts;

   435

   436

        for (var i = 0; i < tiles_len; i++) {

   437

            t = tiles[i];

   438

            ts = t.style;

   439

   440

            ts.width = tw;

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            ts.height = th;

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            ts.top = th*t.__row;

   443

            ts.left = tw*t.__col;

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        }

   445

    },

   446

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});

   450

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// scale the given co-ordinate by a zoom delta. If we zoom in (dz > 0), n will become larger, and if we zoom 

   452

// out (dz < 0), n will become smaller.

   453

function scaleByZoomDelta (n, dz) {

   454

    if (dz > 0)

   455

        return n << dz;

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    else

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        return n >> -dz;

   458

}

   459