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Improve radial gradient sample #8383

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merged 2 commits into from
Feb 5, 2021
Merged

Improve radial gradient sample #8383

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e1154da
Improve radial gradient sample
kurkle Feb 5, 2021
7702da0
Add hover
kurkle Feb 5, 2021
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75 changes: 46 additions & 29 deletions samples/advanced/radial-gradient.html
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Original file line number Diff line number Diff line change
Expand Up @@ -21,10 +21,47 @@
<br>
<button id="randomizeData">Randomize Data</button>
<script>
var chartColors = window.chartColors;
var gradient = null;
var cache = new Map();
var width = null;
var height = null;

function createRadialGradient3(context, c1, c2, c3) {
var chartArea = context.chart.chartArea;
if (!chartArea) {
// This case happens on initial chart load
return null;
}

var chartWidth = chartArea.right - chartArea.left;
var chartHeight = chartArea.bottom - chartArea.top;
if (width !== chartWidth || height !== chartHeight) {
cache.clear();
}
var gradient = cache.get(c1 + c2 + c3);
if (!gradient) {
// Create the gradient because this is either the first render
// or the size of the chart has changed
width = chartWidth;
height = chartHeight;
var centerX = (chartArea.left + chartArea.right) / 2;
var centerY = (chartArea.top + chartArea.bottom) / 2;
var r = Math.min(
(chartArea.right - chartArea.left) / 2,
(chartArea.bottom - chartArea.top) / 2
);
var ctx = context.chart.ctx;
gradient = ctx.createRadialGradient(centerX, centerY, 0, centerX, centerY, r);
gradient.addColorStop(0, c1);
gradient.addColorStop(0.5, c2);
gradient.addColorStop(1, c3);
cache.set(c1 + c2 + c3, gradient);
}

return gradient;
}

var chartColors = window.chartColors;
var colors = [chartColors.red, chartColors.orange, chartColors.yellow, chartColors.green, chartColors.blue];
var config = {
type: 'polarArea',
data: {
Expand All @@ -37,34 +74,14 @@
randomScalingFactor(),
],
backgroundColor: function(context) {
var chartArea = context.chart.chartArea;

if (!chartArea) {
// This case happens on initial chart load
return null;
var c = colors[context.dataIndex];
if (context.active) {
c = Chart.helpers.getHoverColor(c);
}

var chartWidth = chartArea.right - chartArea.left;
var chartHeight = chartArea.bottom - chartArea.top;
if (gradient === null || width !== chartWidth || height !== chartHeight) {
// Create the gradient because this is either the first render
// or the size of the chart has changed
width = chartWidth;
height = chartHeight;
var centerX = (chartArea.left + chartArea.right) / 2;
var centerY = (chartArea.top + chartArea.bottom) / 2;
var r = Math.min(
(chartArea.right - chartArea.left) / 2,
(chartArea.bottom - chartArea.top) / 2
);
var ctx = context.chart.ctx;
gradient = ctx.createRadialGradient(centerX, centerY, 0, centerX, centerY, r);
gradient.addColorStop(0, chartColors.red);
gradient.addColorStop(0.5, chartColors.green);
gradient.addColorStop(1, chartColors.purple);
}

return gradient;
var mid = Chart.helpers.color(c).desaturate(0.2).darken(0.2).rgbString();
var start = Chart.helpers.color(c).lighten(0.2).rotate(270).rgbString();
var end = Chart.helpers.color(c).lighten(0.1).rgbString();
return createRadialGradient3(context, start, mid, end);
},
label: 'My dataset' // for legend
}],
Expand Down