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VistasHow to draw the stroke behind bars in Chart.js?
I've wrote a custom Bar Chart in Chart.JS which on dataset hover highlight the bars by drawing a stroke on it the issue is that stroke is drawn over bars while i would make it something like 'background color' instead.
Like the bars are visible because the stroke color opacity is set to 0.05 while if i set it to 1 obviously those will not be visible anymore.
The code
class CustomBar extends Chart.BarController {
draw() {
super.draw(arguments);
if (this.chart.tooltip._active && this.chart.tooltip._active.length) {
const points = this.chart.tooltip._active[0];
const ctx = this.chart.ctx;
const x = points.element.x;
const topY = points.element.y + 150;
const width = points.element.width;
const bottomY = 0;
ctx.save();
ctx.beginPath();
ctx.moveTo(x, topY * 100);
ctx.lineTo(x + width * 1.3, bottomY);
ctx.lineWidth = width * 4.3;
ctx.strokeStyle = 'rgba(0, 0, 0, 0.05)';
ctx.stroke();
ctx.restore();
}
}
}
CustomBar.id = 'shadowBar';
CustomBar.defaults = Chart.BarController.defaults;
Chart.register(CustomBar);
·
Juan Pablo Isaza
1 Respuestas
Responde la pregunta0
You will need a custom plugin for this, in there you can specify that you want it to draw before the datasets are being drawn. You can do that like so:
Chart.register({
id: 'barShadow',
beforeDatasetsDraw: (chart, args, opts) => {
const {
ctx,
tooltip,
chartArea: {
bottom
}
} = chart;
if (!tooltip || !tooltip._active[0]) {
return
}
const point = tooltip._active[0];
const element = point.element;
const x = element.x;
const topY = -(element.height + 150);
const width = element.width;
const bottomY = 0;
const xOffset = opts.xOffset || 0;
const shadowColor = opts.color || 'rgba(0, 0, 0, 1)';
ctx.save();
ctx.beginPath();
ctx.fillStyle = shadowColor;
ctx.fillRect(x - (element.width / 2) + xOffset, bottom, width * 1.3 * 4.3, topY);
ctx.restore();
}
});
const options = {
type: 'bar',
data: {
labels: ["Red", "Blue", "Yellow", "Green", "Purple", "Orange"],
datasets: [{
label: '# of Votes',
data: [12, 19, 3, 5, 2, 3],
backgroundColor: 'orange'
},
{
label: '# of Points',
data: [7, 11, 5, 8, 3, 7],
backgroundColor: 'pink'
}
]
},
options: {
plugins: {
barShadow: {
xOffset: -10,
color: 'red'
}
}
}
}
const ctx = document.getElementById('chartJSContainer').getContext('2d');
new Chart(ctx, options);<body>
<canvas id="chartJSContainer" width="600" height="400"></canvas>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/3.7.0/chart.js"></script>
</body>
·
Juan Pablo Isaza
Denunciar
Responde la pregunta