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plugin.js
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plugin.js
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'use strict';
import {requestAnimFrame, getStyle} from 'chart.js/helpers';
var STUB_KEY = '$chartjs_deferred';
var MODEL_KEY = '$deferred';
/**
* Plugin based on discussion from Chart.js issue #2745.
* @see https://github.com/chartjs/Chart.js/issues/2745
*/
function defer(fn, delay) {
if (delay) {
window.setTimeout(fn, delay);
} else {
requestAnimFrame.call(window, fn);
}
}
function computeOffset(value, base) {
var number = parseInt(value, 10);
if (isNaN(number)) {
return 0;
} else if (typeof value === 'string' && value.indexOf('%') !== -1) {
return number / 100 * base;
}
return number;
}
function chartInViewport(chart) {
var options = chart[MODEL_KEY].options;
var canvas = chart.canvas;
// https://stackoverflow.com/a/21696585
if (!canvas || canvas.offsetParent === null) {
return false;
}
var rect = canvas.getBoundingClientRect();
var dy = computeOffset(options.yOffset || 0, rect.height);
var dx = computeOffset(options.xOffset || 0, rect.width);
return rect.right - dx >= 0
&& rect.bottom - dy >= 0
&& rect.left + dx <= window.innerWidth
&& rect.top + dy <= window.innerHeight;
}
function onScroll(event) {
var node = event.target;
var stub = node[STUB_KEY];
if (stub.ticking) {
return;
}
stub.ticking = true;
defer(function() {
var charts = stub.charts.slice();
var ilen = charts.length;
var chart, i;
for (i = 0; i < ilen; ++i) {
chart = charts[i];
if (chartInViewport(chart)) {
unwatch(chart); // eslint-disable-line
chart[MODEL_KEY].appeared = true;
chart.update();
}
}
stub.ticking = false;
});
}
function isScrollable(node) {
var type = node.nodeType;
if (type === Node.ELEMENT_NODE) {
var overflowX = getStyle(node, 'overflow-x');
var overflowY = getStyle(node, 'overflow-y');
return overflowX === 'auto' || overflowX === 'scroll'
|| overflowY === 'auto' || overflowY === 'scroll';
}
return node.nodeType === Node.DOCUMENT_NODE;
}
function watch(chart) {
var canvas = chart.canvas;
var parent = canvas.parentElement;
var stub, charts;
while (parent) {
if (isScrollable(parent)) {
stub = parent[STUB_KEY] || (parent[STUB_KEY] = {});
charts = stub.charts || (stub.charts = []);
if (charts.length === 0) {
parent.addEventListener('scroll', onScroll);
}
charts.push(chart);
chart[MODEL_KEY].elements.push(parent);
}
parent = parent.parentElement || parent.ownerDocument;
}
}
function unwatch(chart) {
chart[MODEL_KEY].elements.forEach(function(element) {
var charts = element[STUB_KEY].charts;
charts.splice(charts.indexOf(chart), 1);
if (!charts.length) {
element.removeEventListener('scroll', onScroll);
delete element[STUB_KEY];
}
});
chart[MODEL_KEY].elements = [];
}
export default {
id: 'deferred',
defaults: {
xOffset: 0,
yOffset: 0,
delay: 0
},
beforeInit: function(chart, _, options) {
chart[MODEL_KEY] = {
options: options,
appeared: false,
delayed: false,
loaded: false,
elements: []
};
watch(chart);
},
beforeDatasetsUpdate: function(chart, _, options) {
var model = chart[MODEL_KEY];
if (!model.loaded) {
if (!model.appeared && !chartInViewport(chart)) {
// cancel the datasets update
return false;
}
model.appeared = true;
model.loaded = true;
unwatch(chart);
if (options.delay > 0) {
model.delayed = true;
defer(function() {
// Ensure the chart instance is still alive. It may have been destroyed
// during a delay and calling `chart.update()` will fail. The most common
// reason for such scenario is user navigation.
// https://github.com/chartjs/chartjs-plugin-deferred/pull/14
if (chart.ctx) {
model.delayed = false;
chart.update();
}
}, options.delay);
return false;
}
}
if (model.delayed) {
// in case of delayed update, ensure to block external requests, such
// as interacting with the legend label, or direct calls to update()
return false;
}
},
destroy: function(chart) {
unwatch(chart);
}
};