This example demonstrates using the zoom event to constrain the zoom behavior’s translation. This implementation is a bit heavy-handed, as the translate constraint is zoom-dependent.
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Constrained Zoom
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| .overlay { | |
| fill: none; | |
| pointer-events: all; | |
| } | |
| .land { | |
| fill: #000; | |
| } | |
| .boundary { | |
| fill: none; | |
| stroke: #fff; | |
| stroke-linejoin: round; | |
| stroke-linecap: round; | |
| } | |
| </style> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="//d3js.org/topojson.v1.min.js"></script> | |
| <body> | |
| <script> | |
| var width = 960, | |
| height = 500; | |
| var projection = d3.geo.mercator() | |
| .translate([0, 0]) | |
| .scale(width / 2 / Math.PI); | |
| var zoom = d3.behavior.zoom() | |
| .scaleExtent([1, 8]) | |
| .on("zoom", move); | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height) | |
| .append("g") | |
| .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")") | |
| .call(zoom); | |
| var g = svg.append("g"); | |
| svg.append("rect") | |
| .attr("class", "overlay") | |
| .attr("x", -width / 2) | |
| .attr("y", -height / 2) | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("/mbostock/raw/4090846/world-50m.json", function(error, world) { | |
| if (error) throw error; | |
| g.append("path") | |
| .datum(topojson.feature(world, world.objects.countries)) | |
| .attr("class", "land") | |
| .attr("d", path); | |
| g.append("path") | |
| .datum(topojson.mesh(world, world.objects.countries, function(a, b) { return a !== b; })) | |
| .attr("class", "boundary") | |
| .attr("d", path); | |
| }); | |
| function move() { | |
| var t = d3.event.translate, | |
| s = d3.event.scale; | |
| t[0] = Math.min(width / 2 * (s - 1), Math.max(width / 2 * (1 - s), t[0])); | |
| t[1] = Math.min(height / 2 * (s - 1) + 230 * s, Math.max(height / 2 * (1 - s) - 230 * s, t[1])); | |
| zoom.translate(t); | |
| g.style("stroke-width", 1 / s).attr("transform", "translate(" + t + ")scale(" + s + ")"); | |
| } | |
| </script> |
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