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Use browser lazy loading attribute #55

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Use browser lazy loading attribute #55

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163 changes: 39 additions & 124 deletions assets/gaussholder.js
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Original file line number Diff line number Diff line change
Expand Up @@ -70,134 +70,65 @@ window.Gaussholder = (function (header) {
* @param {HTMLImageElement} element Element to render placeholder for
*/
var handleElement = function (element) {
if ( element.complete ) {
return;
}

if ( ! ( 'gaussholder' in element.dataset ) ) {
return;
}

var canvas = document.createElement('canvas');
var final = element.dataset.gaussholderSize.split(',');

// Set the dimensions...
element.style.width = final[0] + 'px';
element.style.height = final[1] + 'px';

// ...then recalculate based on what it actually renders as
var original = [ final[0], final[1] ];
if ( element.width < final[0] ) {
// Rescale, keeping the aspect ratio
final[0] = element.width;
final[1] = final[1] * ( final[0] / original[0] );
} else if ( element.height < final[1] ) {
// Rescale, keeping the aspect ratio
final[1] = element.height;
final[0] = final[0] * ( final[1] / original[1] );
}

// Set dimensions, _again_
element.style.width = final[0] + 'px';
element.style.height = final[1] + 'px';

render(canvas, element.dataset.gaussholder.split(','), final, function () {
// Load in as our background image
element.style.backgroundImage = 'url("' + canvas.toDataURL() + '")';
element.style.backgroundRepeat = 'no-repeat';
element.style.backgroundSize = 'cover';
element.style.backgroundImage = 'url("' + canvas.toDataURL() + '")';
});

element.onload = function () {
loadOriginal(element);
};
};

var loadOriginal = function (element) {
if ( ! ( 'originalsrc' in element.dataset ) && ! ( 'originalsrcset' in element.dataset ) ) {
return;
}

var data = element.dataset.gaussholderSize.split(','),
radius = parseInt( data[2] );

// Load our image now
var img = new Image();
// Filter property to use
var filterProp = ( 'webkitFilter' in element.style ) ? 'webkitFilter' : 'filter';
element.style[ filterProp ] = 'blur(' + radius * 0.5 + 'px)';

// Ensure blur doesn't bleed past image border
element.style.clipPath = 'url(#gaussclip)'; // Current FF
element.style.clipPath = 'inset(0)'; // Standard
element.style.webkitClipPath = 'inset(0)'; // WebKit

// Clear placeholder temporary image
// (We do this after setting the source, as doing it before can
// cause a tiny flicker)
element.style.backgroundImage = '';
element.style.backgroundRepeat = '';

var start = 0;
var anim = function (ts) {
if ( ! start ) start = ts;
var diff = ts - start;
if ( diff > fadeDuration ) {
element.style[ filterProp ] = '';
element.style.clipPath = '';
element.style.webkitClipPath = '';
return;
}

if ( element.dataset.originalsrc ) {
img.src = element.dataset.originalsrc;
}
if ( element.dataset.originalsrcset ) {
img.srcset = element.dataset.originalsrcset;
}
var effectiveRadius = radius * ( 1 - ( diff / fadeDuration ) );

img.onload = function () {
// Filter property to use
var filterProp = ( 'webkitFilter' in element.style ) ? 'webkitFilter' : 'filter';
element.style[ filterProp ] = 'blur(' + radius * 0.5 + 'px)';

// Ensure blur doesn't bleed past image border
element.style.clipPath = 'url(#gaussclip)'; // Current FF
element.style.clipPath = 'inset(0)'; // Standard
element.style.webkitClipPath = 'inset(0)'; // WebKit

// Set the actual source
element.src = img.src;
element.srcset = img.srcset;

// Cleaning source
element.dataset.originalsrc = '';
element.dataset.originalsrcset = '';

// Clear placeholder temporary image
// (We do this after setting the source, as doing it before can
// cause a tiny flicker)
element.style.backgroundImage = '';
element.style.backgroundRepeat = '';

var start = 0;
var anim = function (ts) {
if ( ! start ) start = ts;
var diff = ts - start;
if ( diff > fadeDuration ) {
element.style[ filterProp ] = '';
element.style.clipPath = '';
element.style.webkitClipPath = '';
return;
}

var effectiveRadius = radius * ( 1 - ( diff / fadeDuration ) );

element.style[ filterProp ] = 'blur(' + effectiveRadius * 0.5 + 'px)';
window.requestAnimationFrame(anim);
};
element.style[ filterProp ] = 'blur(' + effectiveRadius * 0.5 + 'px)';
window.requestAnimationFrame(anim);
};
};

var loadLazily = [];
var threshold = 1200;
var lastRun = 0,
loopTimeout = null;

var scrollHandler = function () {
var now = Date.now();
if ( ( lastRun + 40 ) > now ) {
if ( loopTimeout ) {
return;
}
loopTimeout = window.setTimeout(scrollHandler, 40);
return;
}
lastRun = now;
loopTimeout && (loopTimeout = null);

var next = [];
for (var i = loadLazily.length - 1; i >= 0; i--) {
var img = loadLazily[i];
var shouldShow = img.getBoundingClientRect().top <= ( window.innerHeight + threshold );
if ( ! shouldShow ) {
next.push(img);
continue;
}

loadOriginal(img);
}
loadLazily = next;
if (loadLazily.length < 1) {
window.removeEventListener('scroll', scrollHandler);
}
window.requestAnimationFrame(anim);
};

/**
Expand All @@ -207,23 +138,7 @@ window.Gaussholder = (function (header) {
var images = document.getElementsByTagName('img');

for (var i = images.length - 1; i >= 0; i--) {
var img = images[i];

// Ensure the blank GIF has loaded first
if ( img.complete ) {
handleElement(img);
} else {
img.onload = function () {
handleElement(this);
}
}
}

loadLazily = images;
scrollHandler();

if (loadLazily.length > 0) {
window.addEventListener('scroll', scrollHandler);
handleElement(images[i]);
}
};

Expand Down
2 changes: 1 addition & 1 deletion assets/gaussholder.min.js
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16 changes: 2 additions & 14 deletions inc/frontend/namespace.php
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Original file line number Diff line number Diff line change
Expand Up @@ -130,12 +130,6 @@ function mangle_images( $content ) {

$new_attrs = array();

// Replace src with our blank GIF
$new_attrs[] = 'src="' . esc_attr( $blank_url ) . '"';

// Remove srcset
$new_attrs[] = 'srcset=""';

// Add the actual placeholder
$placeholder = Gaussholder\get_placeholder( $id, $size );
$new_attrs[] = 'data-gaussholder="' . esc_attr( $placeholder ) . '"';
Expand Down Expand Up @@ -163,14 +157,8 @@ function mangle_images( $content ) {
);

$mangled_tag = str_replace(
array(
' srcset="',
' src="',
),
array(
' data-originalsrcset="',
' ' . implode( ' ', $new_attrs ) . ' data-originalsrc="',
),
' src="',
' ' . implode( ' ', $new_attrs ) . ' src="',
$tag
);

Expand Down