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<!DOCTYPE html> |
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<html> |
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<head> |
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<title>Restricted zoom behavior in d3</title> |
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<meta charset="utf-8"> |
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<script src="https://d3js.org/d3.v5.min.js"></script> |
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<style> |
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</style> |
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</head> |
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<body> |
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<script> |
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// first, define your viewport dimensions |
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var width = 960, |
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height = 500; |
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// then, create your svg element and a <g> container |
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// for all of the transformed content |
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var svg = d3.select("body").append("svg") |
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.attr("width", width) |
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.attr("height", height) |
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.style("background-color", randomColor), |
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g = svg.append("g"); |
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// then, create the zoom behvavior |
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var zoom = d3.zoom() |
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// only scale up, e.g. between 1x and 50x |
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.scaleExtent([1, 50]) |
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.on("zoom", function() { |
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// the "zoom" event populates d3.event with an object that has |
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// a "translate" property (a 2-element Array in the form [x, y]) |
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// and a numeric "scale" property |
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var e = d3.event.transform, |
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// now, constrain the x and y components of the translation by the |
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// dimensions of the viewport |
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tx = Math.min(0, Math.max(e.x, width - width * e.k)), |
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ty = Math.min(0, Math.max(e.y, height - height * e.k)); |
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// then, update the zoom behavior's internal translation, so that |
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// it knows how to properly manipulate it on the next movement |
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// and finally, update the <g> element's transform attribute with the |
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// correct translation and scale (in reverse order) |
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g.attr("transform", [ |
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"translate(" + [tx, ty] + ")", |
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"scale(" + e.k + ")" |
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].join(" ")); |
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}); |
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// then, call the zoom behavior on the svg element, which will add |
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// all of the necessary mouse and touch event handlers. |
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// remember that if you call this on the <g> element, the even handlers |
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// will only trigger when the mouse or touch cursor intersects with the |
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// <g> elements' children! |
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svg.call(zoom); |
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// then, let's add some circles |
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var circle = g.selectAll("circle") |
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.data(d3.range(300).map(function(i) { |
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return { |
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x: Math.random() * width, |
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y: Math.random() * height, |
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r: .01 + Math.random() * 50, |
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color: randomColor() |
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}; |
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}).sort(function(a, b) { |
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return d3.descending(a.r, b.r); |
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})) |
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.enter() |
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.append("circle") |
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.attr("fill", function(d) { return d.color; }) |
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.attr("cx", function(d) { return d.x; }) |
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.attr("cy", function(d) { return d.y; }) |
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.attr("r", function(d) { return d.r; }); |
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function randomColor() { |
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return "hsl(" + ~~(60 + Math.random() * 180) + ",80%,60%)"; |
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} |
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</script> |
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</body> |
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</html> |