Time Axis adds +1 tick and changes step length when minimum/maximum is defined

**rpech** · 30 Mar 2012, 7:52 AM

For example, I have a chart (Ext4.chart.Chart) in which I want to display data for last 2 hour's traffic (i.e. last time is 'now' and first time is 'now - 2 hours') and want to have ticks per 15 minutes in format 'now', '15 minutes ago', '30 minutes ago', etc. (in right-to-left order)

So this is what I set for the time axis (Ext4.chart.axis.Time):

Code:

axis.minimum = chartData[0].time; //chartData is simple array loaded via JSON-RPC
axis.maximum = chartData[chartData.length-1].time;
axis.step = [Ext.Date.MINUTE, 15];
chart.refresh();

I would expect to see chart with 9 ticks: 120 minutes ago, 105m ago, ..., 15m ago, now
However Ext generates chart with 10 ticks: 120 minutes ago, 107m ago, 93m ago, ...

As I've discovered, problem is in the method Ext4.chart.axis.Time.calcEnds() which calls Ext4.draw.Draw.snapEndsByDateAndStep(), which uses condition "while (testTo < to)" and since "testTo === to" (i.e. last time exactly match the 15 minute steps) it adds one more step and increases the maximum. Method calcEnds() then uses this number of steps but keeps own maximum and changes the step length (from 15 minutes to 13 minutes and 20 seconds).

It can be fixed by overriding method Ext4.chart.TimeAxis.prototype.calcEnds() and adding the last param to the snapEndsByDateAndStep(..., true) to force the method to keep the defined maximum for all the calculations.

**mitchellsimoens** · 30 Mar 2012, 11:38 AM

Can I get a locally runnable test case? Also what Ext JS 4 version and have you tested outside of the sandbox?

**rpech** · 2 Apr 2012, 2:31 AM

Tested in ExtJS 4.1 RC
Modified from sample Live Updated Chart
Min/Max set to last 2 minutes
Steps set to 15 seconds
(It's exactly same situation as with 2 hours and 15 minute steps)

Current result:
chart_13s.jpg
Expected result:
chart_15s.jpg
Comparison:
chart_bug.jpg

Code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>Chart</title>

    <script type="text/javascript" src="ext-all-debug.js"></script>
    <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1" />

    <link rel="stylesheet" type="text/css" media="screen, projection, print" href="ext-all.css" />

    <script type="text/javascript">
Ext.require([
    'Ext.window.Window',
    'Ext.chart.*'
]);

Ext.onReady(function () {
////FIX - uncomment to get it right
//Ext.chart.TimeAxis.prototype.calcEnds = function() {
//            var me = this, range, step = me.step;
//
//            if (step) {
//                range = me.getRange();
//                range = Ext.draw.Draw.snapEndsByDateAndStep(new Date(range.min), new Date(range.max), Ext.isNumber(step) ? [Date.MILLI, step] : step, true);
//                return range;
//            }
//            else {
//                return me.callParent(arguments);
//            }
//        };
////END of FIX

    var chart;
    var generateData = (function() {
        var data = [],
            last = false,
            min = Math.min,
            max = Math.max,
            random = Math.random;
        return function() {
            data = data.slice();
            data.push({
                date: new Date(),
                visits: min(100, max(last? last.visits + (random() - 0.5) * 20 : random() * 100, 0)),
                views: min(100, max(last? last.views + (random() - 0.5) * 10 : random() * 100, 0)),
                veins: min(100, max(last? last.veins + (random() - 0.5) * 20 : random() * 100, 0))
            });
            last = data[data.length -1];
            return data;
        };
    })();

    var store = Ext.create('Ext.data.JsonStore', {
        fields: ['date', 'visits', 'views', 'veins'],
        data: generateData()
    });

    var intr = setInterval(function() {
//        debugger;
        var data = generateData();
        timeAxis.maximum = +data[data.length-1].date;
        timeAxis.minimum = +data[data.length-1].date - 2*60*1000; //2 minutes
        timeAxis.step = [Ext.Date.SECOND, 15];
        store.loadData(data);
    }, 1000);

    Ext.create('Ext.Window', {
        width: 800,
        height: 600,
        minHeight: 400,
        minWidth: 550,
        maximizable: true,
        title: 'Live Updated Chart',
        layout: 'fit',
        items: [{
            xtype: 'chart',
            style: 'background:#fff',
            store: store,
            grid: true,
            id: 'chartCmp',
            axes: [{
                type: 'Numeric',
                grid: true,
                minimum: 0,
                maximum: 100,
                position: 'left',
                fields: ['views', 'visits', 'veins'],
                title: 'Number of Hits',
                grid: {
                    odd: {
                        fill: '#dedede',
                        stroke: '#ddd',
                        'stroke-width': 0.5
                    }
                }
            }, {
                type: 'Time',
                position: 'bottom',
                fields: 'date',
                title: 'Time',
                label: {
                    renderer: function(value) {
                        if (!timeAxis) { return ''; }

                        var
                            max = timeAxis.maximum,
                            e = Ext.Date.getElapsed(value, max),
                            s = Math.floor(e/1000);

                         return (0 === s) ? 'now' : s + 's ago';
                    }
                },
                constrain: true
            }],
            series: [{
                type: 'line',
                axis: ['left', 'bottom'],
                xField: 'date',
                yField: 'visits',
                label: {
                    display: 'none',
                    field: 'visits',
                    renderer: function(v) { return v >> 0; },
                    'text-anchor': 'middle'
                },
                markerConfig: {
                    radius: 5,
                    size: 5
                }
            },{
                type: 'line',
                axis: ['left', 'bottom'],
                xField: 'date',
                yField: 'views',
                label: {
                    display: 'none',
                    field: 'visits',
                    renderer: function(v) { return v >> 0; },
                    'text-anchor': 'middle'
                },
                markerConfig: {
                    radius: 5,
                    size: 5
                }
            },{
                type: 'line',
                axis: ['left', 'bottom'],
                xField: 'date',
                yField: 'veins',
                label: {
                    display: 'none',
                    field: 'visits',
                    renderer: function(v) { return v >> 0; },
                    'text-anchor': 'middle'
                },
                markerConfig: {
                    radius: 5,
                    size: 5
                }
            }]
        }]
    }).show();
    chart = Ext.getCmp('chartCmp');
    var timeAxis = chart.axes.get(1);
});
    </script>

</head>
<body>
<h1>Chart</h1>
</body>
</html>

Fix included in the code.

//edit:
tested in:
Windows 7 x64: Firefox 11, IE9 x64, Safari 5.1, Chrome 18
MaxOS 10.6.8: Safari 5.1, Chrome 17, Firefox 3.6

Live sample:
http://ext-chart.chobits.ch/bad.html
http://ext-chart.chobits.ch/good.html

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