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@larskotthoff
Forked from mbostock/.block
Created February 4, 2015 18:51
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This brush snaps to day boundaries. When the user releases the brush, the brush fires a brushend event, allowing a listener to adjust the brush extent. Using the new brush transitions released in D3 3.3, the brush smoothly interpolates from the original extent to the rounded extent. Compare this approach to using immediate snapping while brushing.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
.axis text {
font: 11px sans-serif;
}
.axis path {
display: none;
}
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.grid-background {
fill: #ddd;
}
.grid line,
.grid path {
fill: none;
stroke: #fff;
shape-rendering: crispEdges;
}
.grid .minor.tick line {
stroke-opacity: .5;
}
.brush .extent {
stroke: #000;
fill-opacity: .125;
shape-rendering: crispEdges;
}
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 200, right: 40, bottom: 200, left: 40},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var x = d3.time.scale()
.domain([new Date(2013, 7, 1), new Date(2013, 7, 15) - 1])
.range([0, width]);
var brush = d3.svg.brush()
.x(x)
.extent([new Date(2013, 7, 2), new Date(2013, 7, 3)])
.on("brushend", brushended);
var svg = d3.select("body").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
svg.append("rect")
.attr("class", "grid-background")
.attr("width", width)
.attr("height", height);
svg.append("g")
.attr("class", "x grid")
.attr("transform", "translate(0," + height + ")")
.call(d3.svg.axis()
.scale(x)
.orient("bottom")
.ticks(d3.time.hours, 12)
.tickSize(-height)
.tickFormat(""))
.selectAll(".tick")
.classed("minor", function(d) { return d.getHours(); });
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(d3.svg.axis()
.scale(x)
.orient("bottom")
.ticks(d3.time.days)
.tickPadding(0))
.selectAll("text")
.attr("x", 6)
.style("text-anchor", null);
var gBrush = svg.append("g")
.attr("class", "brush")
.call(brush);
gBrush.selectAll("rect")
.attr("height", height);
function brushended() {
if (!d3.event.sourceEvent) return; // only transition after input
var extent0 = brush.extent(),
extent1 = extent0.map(d3.time.day.round);
// if empty when rounded, use floor & ceil instead
if (extent1[0] >= extent1[1]) {
extent1[0] = d3.time.day.floor(extent0[0]);
extent1[1] = d3.time.day.ceil(extent0[1]);
}
d3.select(this)
.call(brush.extent(extent1))
.call(brush.event);
}
</script>
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