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 /* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 // The possible values of the "align" component of preserveAspectRatio.

 const ALIGN_VALS = ["none",

                     "xMinYMin", "xMinYMid", "xMinYMax",

                     "xMidYMin", "xMidYMid", "xMidYMax",

                     "xMaxYMin", "xMaxYMid", "xMaxYMax"];

 // The possible values of the "meetOrSlice" component of preserveAspectRatio.

 const MEETORSLICE_VALS = [ "meet", "slice" ];

 const SVGNS   = "http://www.w3.org/2000/svg";

 const XLINKNS = "http://www.w3.org/1999/xlink";

 // This is the separation between the x & y values of each <image> in a

 // generated grid.

 const IMAGE_OFFSET = 50;

 function generateBorderRect(aX, aY, aWidth, aHeight) {

   var rect = document.createElementNS(SVGNS, "rect");

   rect.setAttribute("x", aX);

   rect.setAttribute("y", aY);

   rect.setAttribute("width", aWidth);

   rect.setAttribute("height", aHeight);

   rect.setAttribute("fill", "none");

   rect.setAttribute("stroke", "black");

   rect.setAttribute("stroke-width", "2");

   rect.setAttribute("stroke-dasharray", "3 2");

   return rect;

 }

 // Returns an SVG <image> element with the given xlink:href, width, height,

 // and preserveAspectRatio=[aAlign aMeetOrSlice] attributes

 function generateImageElementForParams(aX, aY, aWidth, aHeight,

                                        aHref, aAlign, aMeetOrSlice) {

   var image = document.createElementNS(SVGNS, "image");

   image.setAttribute("x", aX);

   image.setAttribute("y", aY);

   image.setAttribute("width", aWidth);

   image.setAttribute("height", aHeight);

   image.setAttributeNS(XLINKNS, "href", aHref);

   image.setAttribute("preserveAspectRatio", aAlign + " " + aMeetOrSlice);

   return image;

 }

 // Returns a <g> element filled with a grid of <image> elements which each

 // have the specified aWidth & aHeight and which use all possible values of

 // preserveAspectRatio.

 //

 // The final "aBonusPARVal" argument (if specified) is used as the

 // preserveAspectRatio value on a bonus <image> element, added at the end.

 function generateImageGrid(aHref, aWidth, aHeight, aBonusPARVal) {

   var grid = document.createElementNS(SVGNS, "g");

   var y = 0;

   var x = 0;

   for (var i = 0; i < ALIGN_VALS.length; i++) {

     // Jump to next line of grid, for every other "i" value.

     // (every fourth entry)

     if (i && i % 2 == 0) {

       y += IMAGE_OFFSET;

       x = 0;

     }

     var alignVal = ALIGN_VALS[i];

     for (var j = 0; j < MEETORSLICE_VALS.length; j++) {

       var meetorsliceVal = MEETORSLICE_VALS[j];

       var border = generateBorderRect(x, y, aWidth, aHeight);

       var image  = generateImageElementForParams(x, y, aWidth, aHeight,

                                                  aHref, alignVal,

                                                  meetorsliceVal);

       grid.appendChild(border);

       grid.appendChild(image);

       x += IMAGE_OFFSET;

     }

   }

   if (aBonusPARVal) {

     // Add one final entry with "bonus" pAR value.

     y += IMAGE_OFFSET;

     x = 0;

     var border = generateBorderRect(x, y, aWidth, aHeight);

     var image  = generateImageElementForParams(x, y, aWidth, aHeight,

                                                aHref, aBonusPARVal, "");

     grid.appendChild(border);

     grid.appendChild(image);

   }

   return grid;

 }

 // Returns an SVG <symbol> element that...

 //  (a) has the given ID

 //  (b) contains only a <use> element to the given URI

 //  (c) has a hardcoded viewBox="0 0 10 10" attribute

 //  (d) has the given preserveAspectRatio=[aAlign aMeetOrSlice] attribute

 function generateSymbolElementForParams(aSymbolID, aHref,

                                         aAlign, aMeetOrSlice) {

   var use = document.createElementNS(SVGNS, "use");

   use.setAttributeNS(XLINKNS, "href", aHref);

   var symbol = document.createElementNS(SVGNS, "symbol");

   symbol.setAttribute("id", aSymbolID);

   symbol.setAttribute("viewBox", "0 0 10 10");

   symbol.setAttribute("preserveAspectRatio", aAlign + " " + aMeetOrSlice);

   symbol.appendChild(use);

   return symbol;

 }

 function generateUseElementForParams(aTargetURI, aX, aY, aWidth, aHeight) {

   var use = document.createElementNS(SVGNS, "use");

   use.setAttributeNS(XLINKNS, "href", aTargetURI);

   use.setAttribute("x", aX);

   use.setAttribute("y", aY);

   use.setAttribute("width", aWidth);

   use.setAttribute("height", aHeight);

   return use;

 }

 // Returns a <g> element filled with a grid of <use> elements which each

 // have the specified aWidth & aHeight and which reference <symbol> elements

 // with all possible values of preserveAspectRatio.  Each <symbol> contains

 // a <use> that links to the given URI, aHref.

 //

 // The final "aBonusPARVal" argument (if specified) is used as the

 // preserveAspectRatio value on a bonus <symbol> element, added at the end.

 function generateSymbolGrid(aHref, aWidth, aHeight, aBonusPARVal) {

   var grid = document.createElementNS(SVGNS, "g");

   var y = 0;

   var x = 0;

   for (var i = 0; i < ALIGN_VALS.length; i++) {

     // Jump to next line of grid, for every other "i" value.

     // (every fourth entry)

     if (i && i % 2 == 0) {

       y += IMAGE_OFFSET;

       x = 0;

     }

     var alignVal = ALIGN_VALS[i];

     for (var j = 0; j < MEETORSLICE_VALS.length; j++) {

       var meetorsliceVal = MEETORSLICE_VALS[j];

       var border = generateBorderRect(x, y, aWidth, aHeight);

       var symbolID = "symbol_" + alignVal + "_" + meetorsliceVal;

       var symbol = generateSymbolElementForParams(symbolID, aHref,

                                                   alignVal, meetorsliceVal);

       var use = generateUseElementForParams("#" + symbolID,

                                             x, y, aWidth, aHeight);

       grid.appendChild(symbol); // This isn't painted

       grid.appendChild(border);

       grid.appendChild(use);

       x += IMAGE_OFFSET;

     }

   }

   if (aBonusPARVal) {

     // Add one final entry with "bonus" pAR value.

     y += IMAGE_OFFSET;

     x = 0;

     var border = generateBorderRect(x, y, aWidth, aHeight);

     var symbolID = "symbol_Bonus";

     var symbol = generateSymbolElementForParams(symbolID, aHref,

                                                 aBonusPARVal, "");

     var use = generateUseElementForParams("#" + symbolID,

                                           x, y, aWidth, aHeight);

     grid.appendChild(symbol); // This isn't painted

     grid.appendChild(border);

     grid.appendChild(use);

   }

   return grid;

 }