1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
|
import { debounce, throttle } from 'lodash';
export const placeholderImage =
'data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==';
const SCROLL_THRESHOLD = 500;
export default class LazyLoader {
constructor(options = {}) {
this.intersectionObserver = null;
this.lazyImages = [];
this.observerNode = options.observerNode || '#content-body';
const scrollContainer = options.scrollContainer || window;
scrollContainer.addEventListener('load', () => this.register());
}
static supportsNativeLazyLoading() {
return 'loading' in HTMLImageElement.prototype;
}
static supportsIntersectionObserver() {
return Boolean(window.IntersectionObserver);
}
searchLazyImages() {
window.requestIdleCallback(
() => {
const lazyImages = [].slice.call(document.querySelectorAll('.lazy'));
if (LazyLoader.supportsNativeLazyLoading()) {
lazyImages.forEach(img => LazyLoader.loadImage(img));
} else if (LazyLoader.supportsIntersectionObserver()) {
if (this.intersectionObserver) {
lazyImages.forEach(img => this.intersectionObserver.observe(img));
}
} else if (lazyImages.length) {
this.lazyImages = lazyImages;
this.checkElementsInView();
}
},
{ timeout: 500 },
);
}
startContentObserver() {
const contentNode = document.querySelector(this.observerNode) || document.querySelector('body');
if (contentNode) {
this.mutationObserver = new MutationObserver(() => this.searchLazyImages());
this.mutationObserver.observe(contentNode, {
childList: true,
subtree: true,
});
}
}
stopContentObserver() {
if (this.mutationObserver) {
this.mutationObserver.takeRecords();
this.mutationObserver.disconnect();
this.mutationObserver = null;
}
}
unregister() {
this.stopContentObserver();
if (this.intersectionObserver) {
this.intersectionObserver.takeRecords();
this.intersectionObserver.disconnect();
this.intersectionObserver = null;
}
if (this.throttledScrollCheck) {
window.removeEventListener('scroll', this.throttledScrollCheck);
}
if (this.debouncedElementsInView) {
window.removeEventListener('resize', this.debouncedElementsInView);
}
}
register() {
if (!LazyLoader.supportsNativeLazyLoading()) {
if (LazyLoader.supportsIntersectionObserver()) {
this.startIntersectionObserver();
} else {
this.startLegacyObserver();
}
}
this.startContentObserver();
this.searchLazyImages();
}
startIntersectionObserver = () => {
this.throttledElementsInView = throttle(() => this.checkElementsInView(), 300);
this.intersectionObserver = new IntersectionObserver(this.onIntersection, {
rootMargin: `${SCROLL_THRESHOLD}px 0px`,
thresholds: 0.1,
});
};
onIntersection = entries => {
entries.forEach(entry => {
// We are using `intersectionRatio > 0` over `isIntersecting`, as some browsers did not ship the latter
// See: https://gitlab.com/gitlab-org/gitlab-foss/issues/54407
if (entry.intersectionRatio > 0) {
this.intersectionObserver.unobserve(entry.target);
this.lazyImages.push(entry.target);
}
});
this.throttledElementsInView();
};
startLegacyObserver() {
this.throttledScrollCheck = throttle(() => this.scrollCheck(), 300);
this.debouncedElementsInView = debounce(() => this.checkElementsInView(), 300);
window.addEventListener('scroll', this.throttledScrollCheck);
window.addEventListener('resize', this.debouncedElementsInView);
}
scrollCheck() {
window.requestAnimationFrame(() => this.checkElementsInView());
}
checkElementsInView() {
const scrollTop = window.pageYOffset;
const visHeight = scrollTop + window.innerHeight + SCROLL_THRESHOLD;
// Loading Images which are in the current viewport or close to them
this.lazyImages = this.lazyImages.filter(selectedImage => {
if (selectedImage.getAttribute('data-src')) {
const imgBoundRect = selectedImage.getBoundingClientRect();
const imgTop = scrollTop + imgBoundRect.top;
const imgBound = imgTop + imgBoundRect.height;
if (scrollTop <= imgBound && visHeight >= imgTop) {
window.requestAnimationFrame(() => {
LazyLoader.loadImage(selectedImage);
});
return false;
}
/*
If we are scrolling fast, the img we watched intersecting could have left the view port.
So we are going watch for new intersections.
*/
if (LazyLoader.supportsIntersectionObserver()) {
if (this.intersectionObserver) {
this.intersectionObserver.observe(selectedImage);
}
return false;
}
return true;
}
return false;
});
}
static loadImage(img) {
if (img.getAttribute('data-src')) {
img.setAttribute('loading', 'lazy');
let imgUrl = img.getAttribute('data-src');
// Only adding width + height for avatars for now
if (imgUrl.indexOf('/avatar/') > -1 && imgUrl.indexOf('?') === -1) {
const targetWidth = img.getAttribute('width') || img.width;
imgUrl += `?width=${targetWidth}`;
}
img.setAttribute('src', imgUrl);
img.removeAttribute('data-src');
img.classList.remove('lazy');
img.classList.add('js-lazy-loaded');
img.classList.add('qa-js-lazy-loaded');
}
}
}
|
