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copied!<p>It took me a while, but I finally got the math clean. This solution requires three things:</p> <ol> <li>Include <a href="http://phrogz.net/svg/libraries/SVGPanUnscale.js" rel="noreferrer">this script</a> in your page (along with the SVGPan.js script), e.g.<br> <code><script xlink:href="SVGPanUnscale.js"></script></code></li> <li>Identify the items you want not to scale (e.g. place them in a group with a special class or ID, or put a particular class on each element) and then tell the script how to find those items, e.g.<br> <code>unscaleEach("g.non-scaling > *, circle.non-scaling");</code></li> <li><strong>Use <code>transform="translate(…,…)"</code> to place each element on the diagram, <em>not</em> <code>cx="…" cy="…"</code>.</strong></li> </ol> <p>With just those steps, zooming and panning using SVGPan will not affect the scale (or rotation, or skew) of marked elements.</p> <h2>Demo: <a href="http://phrogz.net/svg/scale-independent-elements.svg" rel="noreferrer">http://phrogz.net/svg/scale-independent-elements.svg</a></h2> <h2>Library</h2> <pre class="lang-js prettyprint-override"><code>// Copyright 2012 © Gavin Kistner, !@phrogz.net // License: http://phrogz.net/JS/_ReuseLicense.txt // Undo the scaling to selected elements inside an SVGPan viewport function unscaleEach(selector){ if (!selector) selector = "g.non-scaling > *"; window.addEventListener('mousewheel', unzoom, false); window.addEventListener('DOMMouseScroll', unzoom, false); function unzoom(evt){ // getRoot is a global function exposed by SVGPan var r = getRoot(evt.target.ownerDocument); [].forEach.call(r.querySelectorAll(selector), unscale); } } // Counteract all transforms applied above an element. // Apply a translation to the element to have it remain at a local position function unscale(el){ var svg = el.ownerSVGElement; var xf = el.scaleIndependentXForm; if (!xf){ // Keep a single transform matrix in the stack for fighting transformations // Be sure to apply this transform after existing transforms (translate) xf = el.scaleIndependentXForm = svg.createSVGTransform(); el.transform.baseVal.appendItem(xf); } var m = svg.getTransformToElement(el.parentNode); m.e = m.f = 0; // Ignore (preserve) any translations done up to this point xf.setMatrix(m); } </code></pre> <h2>Demo Code</h2> <pre class="lang-svg prettyprint-override"><code><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"> <title>Scale-Independent Elements</title> <style> polyline { fill:none; stroke:#000; vector-effect:non-scaling-stroke; } circle, polygon { fill:#ff9; stroke:#f00; opacity:0.5 } </style> <g id="viewport" transform="translate(500,300)"> <polyline points="-100,-50 50,75 100,50" /> <g class="non-scaling"> <circle transform="translate(-100,-50)" r="10" /> <polygon transform="translate(100,50)" points="0,-10 10,0 0,10 -10,0" /> </g> <circle class="non-scaling" transform="translate(50,75)" r="10" /> </g> <script xlink:href="SVGPan.js"></script> <script xlink:href="SVGPanUnscale.js"></script> <script> unscaleEach("g.non-scaling > *, circle.non-scaling"); </script> </svg> </code></pre>

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