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horizontal.html
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horizontal.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
body {
margin: 0;
--indifference-class-gap: 1.3rem;
}
.weak-order {
background-color: #ddd;
padding: 1rem;
margin-top: 1rem;
display: flex;
flex-direction: row;
}
.indifference-class {
display: flex;
flex-direction: row;
margin-left: calc(var(--indifference-class-gap) / 2);
margin-right: calc(-1 * var(--indifference-class-gap) / 2);
transition: margin 70ms ease-in-out; /* for animation */
}
.indifference-class:has(.item) {
margin-left: var(--indifference-class-gap);
margin-right: 0;
}
.item {
user-select: none;
width: 3rem;
height: 3rem;
line-height: 3rem;
text-align: center;
background-color: white;
box-sizing: border-box;
border: 1px solid black;
margin-left: -1px; /* to prevent double border */
cursor: move;
}
.item:first-child {
margin-left: 0;
}
.item.dragging {
background-color: antiquewhite;
}
</style>
</head>
<body>
<div class="weak-order">
<div class="indifference-class">
<div class="item" draggable="true">1</div>
<div class="item" draggable="true">2</div>
</div>
<div class="indifference-class">
<div class="item" draggable="true">3</div>
<div class="item" draggable="true">4</div>
</div>
<div class="indifference-class">
<div class="item" draggable="true">5</div>
<div class="item" draggable="true">6</div>
</div>
</div>
<script>
const items = document.querySelectorAll('.item');
const weakOrders = document.querySelectorAll('.weak-order');
function createEmptyIndifferenceClass() {
const emptyIndifferenceClass = document.createElement('div');
emptyIndifferenceClass.classList.add('indifference-class');
return emptyIndifferenceClass;
}
function removeEmptyIndifferenceClasses(weakOrder) {
const emptyIndifferenceClasses = [...weakOrder.querySelectorAll('.indifference-class')].filter(indifferenceClass => {
return indifferenceClass.children.length === 0;
});
emptyIndifferenceClasses.forEach(emptyIndifferenceClass => {
emptyIndifferenceClass.remove();
});
}
items.forEach(item => {
item.addEventListener('dragstart', (e) => {
item.classList.add('dragging');
item.dataset.justStartedDragging = true;
e.dataTransfer.setData('text/plain', item.textContent); // safari needs this
e.dataTransfer.effectAllowed = "move"; // cursor
})
item.addEventListener('dragend', () => {
const weakOrder = document.querySelector('.weak-order:has(.dragging)');
removeEmptyIndifferenceClasses(weakOrder);
item.classList.remove('dragging');
})
})
weakOrders.forEach(weakOrder => {
weakOrder.addEventListener('dragover', e => {
const item = document.querySelector('.dragging');
// check if item can be dropped here (originates from the same weak order)
if (!item.parentElement || !item.parentElement.parentElement || item.parentElement.parentElement !== weakOrder) {
return;
}
e.preventDefault()
const indifferenceClasses = [...weakOrder.querySelectorAll('.indifference-class')];
// target indifference class
const indifferenceClass = getIndifferenceClassAtX(weakOrder, e.clientX);
// is it currently empty, so that the item will create a "new" indifference class?
const indifferenceClassEmpty = indifferenceClass.children.length === 0;
// optimization: store information for later
// if the indifference class hasn't changed, we don't need to update empty indifference classes later
// exception: when we just started dragging, we need to draw initial new empty indifference classes
const stayedInSameIndifferenceClass = indifferenceClass == item.parentElement;
const justStartedDragging = item.dataset.justStartedDragging;
item.dataset.justStartedDragging = "";
// place item
const afterElement = getItemAtX(indifferenceClass, e.clientX);
const shouldAnimate = !stayedInSameIndifferenceClass && !indifferenceClassEmpty;
const animationOptions = {duration: 70, easing: 'ease-in-out'}
if (afterElement == null) {
if (shouldAnimate) {
item.animate([{ marginLeft: 'var(--indifference-class-gap)' }, { marginLeft: '0' }], animationOptions);
}
indifferenceClass.appendChild(item);
} else {
if (shouldAnimate) {
item.animate([{ marginRight: 'var(--indifference-class-gap)' }, { marginRight: '0' }], animationOptions);
}
indifferenceClass.insertBefore(item, afterElement);
}
// skip unnecessary updates
if (stayedInSameIndifferenceClass && !justStartedDragging) {
return;
}
// delete empty indifference classes
removeEmptyIndifferenceClasses(weakOrder);
// make empty indifference classes
if (indifferenceClass.children.length >= 2) {
// left
const leftEmptyIndifferenceClass = createEmptyIndifferenceClass();
weakOrder.insertBefore(leftEmptyIndifferenceClass, indifferenceClass);
// right
const rightEmptyIndifferenceClass = createEmptyIndifferenceClass();
weakOrder.insertBefore(rightEmptyIndifferenceClass, indifferenceClass.nextElementSibling);
}
})
})
function getIndifferenceClassAtX(weakOrder, x) {
const classes = [...weakOrder.querySelectorAll('.indifference-class')];
let nextClass = classes.find(elem => {
return x <= elem.getBoundingClientRect().left + elem.getBoundingClientRect().width;
});
if (!nextClass) {
nextClass = classes[classes.length - 1];
}
return nextClass;
}
function getItemAtX(indifferenceClass, x) {
const items = [...indifferenceClass.querySelectorAll('.item:not(.dragging)')];
let nextItem = items.find(item => {
return x <= item.getBoundingClientRect().left + item.getBoundingClientRect().width / 2;
});
return nextItem;
}
</script>
<!-- polyfill -->
<script src="DragDropTouch.js"></script>
</body>
</html>