UI: Add some simple accessibility labels for line charts

ui/app/components/line-chart.js

@@ -37,6 +37,9 @@ export default Component.extend(WindowResizable, {
   timeseries: false,
   chartClass: 'is-primary',
 
+  title: 'Line Chart',
+  description: null,
+
   // Private Properties
 
   width: 0,
@@ -96,6 +99,22 @@ export default Component.extend(WindowResizable, {
     return scale;
   }),
 
+  xRange: computed('data.[]', 'xFormat', 'xProp', 'timeseries', function() {
+    const { xProp, timeseries, data } = this.getProperties('xProp', 'timeseries', 'data');
+    const range = d3Array.extent(data, d => d[xProp]);
+    const formatter = this.xFormat(timeseries);
+
+    return range.map(formatter);
+  }),
+
+  yRange: computed('data.[]', 'yFormat', 'yProp', function() {
+    const yProp = this.get('yProp');
+    const range = d3Array.extent(this.get('data'), d => d[yProp]);
+    const formatter = this.yFormat();
+
+    return range.map(formatter);
+  }),
+
   yScale: computed('data.[]', 'yProp', 'xAxisOffset', function() {
     const yProp = this.get('yProp');
     let max = d3Array.max(this.get('data'), d => d[yProp]) || 1;

ui/app/components/stats-time-series.js

@@ -5,6 +5,7 @@ import d3Format from 'd3-format';
 import d3Scale from 'd3-scale';
 import d3Array from 'd3-array';
 import LineChart from 'nomad-ui/components/line-chart';
+import formatDuration from 'nomad-ui/utils/format-duration';
 
 export default LineChart.extend({
   xProp: 'timestamp',
@@ -19,6 +20,20 @@ export default LineChart.extend({
     return d3Format.format('.1~%');
   },
 
+  // Specific a11y descriptors
+  title: 'Stats Time Series Chart',
+
+  description: computed('data.[]', 'xProp', 'yProp', function() {
+    const { xProp, yProp, data } = this.getProperties('data', 'xProp', 'yProp');
+    const yRange = d3Array.extent(data, d => d[yProp]);
+    const xRange = d3Array.extent(data, d => d[xProp]);
+    const yFormatter = this.yFormat();
+
+    const duration = formatDuration(xRange[1] - xRange[0], 'ms', true);
+
+    return `Time series data for the last ${duration}, with values ranging from ${yFormatter(yRange[0])} to ${yFormatter(yRange[1])}`;
+  }),
+
   xScale: computed('data.[]', 'xProp', 'timeseries', 'yAxisOffset', function() {
     const xProp = this.get('xProp');
     const scale = this.get('timeseries') ? d3Scale.scaleTime() : d3Scale.scaleLinear();

ui/app/helpers/format-duration.js

@@ -1,8 +1,8 @@
 import Helper from '@ember/component/helper';
 import formatDuration from '../utils/format-duration';
 
-function formatDurationHelper([duration], { units }) {
-  return formatDuration(duration, units);
+function formatDurationHelper([duration], { units, longForm }) {
+  return formatDuration(duration, units, longForm);
 }
 
 export default Helper.helper(formatDurationHelper);

ui/app/templates/components/line-chart.hbs

@@ -1,4 +1,13 @@
-<svg data-test-line-chart>
+<svg data-test-line-chart role="img" aria-labelledby="{{concat "title-" elementId}} {{concat "desc-" elementId}}">
+  <title id="{{concat "title-" elementId}}">{{title}}</title>
+  <description id="{{concat "desc-" elementId}}">
+    {{#if description}}
+      {{description}}
+    {{else}}
+      X-axis values range from {{xRange.firstObject}} to {{xRange.lastObject}},
+      and Y-axis values range from {{yRange.firstObject}} to {{yRange.lastObject}}.
+    {{/if}}
+  </description>
   <defs>
     <linearGradient x1="0" x2="0" y1="0" y2="1" class="{{chartClass}}" id="{{fillId}}">
       <stop class="start" offset="0%" />
@@ -14,8 +23,8 @@
     <rect class="area" x="0" y="0" width="{{yAxisOffset}}" height="{{xAxisOffset}}" fill="url(#{{fillId}})" clip-path="url(#{{maskId}})" />
     <rect class="hover-target" x="0" y="0" width="{{yAxisOffset}}" height="{{xAxisOffset}}" />
   </g>
-  <g class="x-axis axis" transform="translate(0, {{xAxisOffset}})"></g>
-  <g class="y-axis axis" transform="translate({{yAxisOffset}}, 0)"></g>
+  <g aria-hidden="true" class="x-axis axis" transform="translate(0, {{xAxisOffset}})"></g>
+  <g aria-hidden="true" class="y-axis axis" transform="translate({{yAxisOffset}}, 0)"></g>
 </svg>
 <div class="chart-tooltip is-snappy {{if isActive "active" "inactive"}}" style={{tooltipStyle}}>
   <p>

ui/app/utils/format-duration.js

@@ -1,18 +1,52 @@
 import moment from 'moment';
 
+/**
+ * Metadata for all unit types
+ * name: identifier for the unit. Also maps to moment methods when applicable
+ * suffix: the preferred suffix for a unit
+ * inMoment: whether or not moment can be used to compute this unit value
+ * pluralizable: whether or not this suffix can be pluralized
+ * longSuffix: the suffix to use instead of suffix when longForm is true
+ */
 const allUnits = [
   { name: 'years', suffix: 'year', inMoment: true, pluralizable: true },
   { name: 'months', suffix: 'month', inMoment: true, pluralizable: true },
   { name: 'days', suffix: 'day', inMoment: true, pluralizable: true },
-  { name: 'hours', suffix: 'h', inMoment: true, pluralizable: false },
-  { name: 'minutes', suffix: 'm', inMoment: true, pluralizable: false },
-  { name: 'seconds', suffix: 's', inMoment: true, pluralizable: false },
+  { name: 'hours', suffix: 'h', longSuffix: 'hour', inMoment: true, pluralizable: false },
+  { name: 'minutes', suffix: 'm', longSuffix: 'minute', inMoment: true, pluralizable: false },
+  { name: 'seconds', suffix: 's', longSuffix: 'second', inMoment: true, pluralizable: false },
   { name: 'milliseconds', suffix: 'ms', inMoment: true, pluralizable: false },
   { name: 'microseconds', suffix: 'µs', inMoment: false, pluralizable: false },
   { name: 'nanoseconds', suffix: 'ns', inMoment: false, pluralizable: false },
 ];
 
-export default function formatDuration(duration = 0, units = 'ns') {
+const pluralizeUnits = (amount, unit, longForm) => {
+  let suffix;
+
+  if (longForm && unit.longSuffix) {
+    // Long form means always using full words (seconds insteand of s) which means
+    // pluralization is necessary.
+    suffix = amount === 1 ? unit.longSuffix : unit.longSuffix.pluralize();
+  } else {
+    // In the normal case, only pluralize based on the pluralizable flag
+    suffix = amount === 1 || !unit.pluralizable ? unit.suffix : unit.suffix.pluralize();
+  }
+
+  // A space should go between the value and the unit when the unit is a full word
+  // 300ns vs. 1 hour
+  const addSpace = unit.pluralizable || (longForm && unit.longSuffix);
+  return `${amount}${addSpace ? ' ' : ''}${suffix}`;
+};
+
+/**
+ * Format a Duration at a preferred precision
+ *
+ * @param {Number} duration The duration to format
+ * @param {String} units The units for the duration. Default to nanoseconds.
+ * @param {Boolean} longForm Whether or not to expand single character suffixes,
+ *   used to ensure screen readers correctly read units.
+ */
+export default function formatDuration(duration = 0, units = 'ns', longForm = false) {
   const durationParts = {};
 
   // Moment only handles up to millisecond precision.
@@ -46,9 +80,7 @@ export default function formatDuration(duration = 0, units = 'ns') {
   const displayParts = allUnits.reduce((parts, unitType) => {
     if (durationParts[unitType.name]) {
       const count = durationParts[unitType.name];
-      const suffix =
-        count === 1 || !unitType.pluralizable ? unitType.suffix : unitType.suffix.pluralize();
-      parts.push(`${count}${unitType.pluralizable ? ' ' : ''}${suffix}`);
+      parts.push(pluralizeUnits(count, unitType, longForm));
     }
     return parts;
   }, []);
@@ -58,7 +90,5 @@ export default function formatDuration(duration = 0, units = 'ns') {
   }
 
   // When the duration is 0, show 0 in terms of `units`
-  const unitTypeForUnits = allUnits.findBy('suffix', units);
-  const suffix = unitTypeForUnits.pluralizable ? units.pluralize() : units;
-  return `0${unitTypeForUnits.pluralizable ? ' ' : ''}${suffix}`;
+  return pluralizeUnits(0, allUnits.findBy('suffix', units), longForm);
 }

ui/tests/unit/utils/format-duration-test.js

@@ -26,3 +26,10 @@ test('When duration is 0, 0 is shown in terms of the units provided to the funct
   assert.equal(formatDuration(0), '0ns', 'formatDuration(0) -> 0ns');
   assert.equal(formatDuration(0, 'year'), '0 years', 'formatDuration(0, "year") -> 0 years');
 });
+
+test('The longForm option expands suffixes to words', function(assert) {
+  const expectation1 = '3 seconds 20ms';
+  const expectation2 = '5 hours 59 minutes';
+  assert.equal(formatDuration(3020, 'ms', true), expectation1, expectation1);
+  assert.equal(formatDuration(60 * 5 + 59, 'm', true), expectation2, expectation2);
+});