SO Javascript drag/drop - Illustrator style 'smart guides'
Answer to http://stackoverflow.com/questions/20075009/javascript-drag-drop-illustrator-style-smart-guides
HTML
<div class='parent'>
<div class='object'></div>
<div class='other-object' style="top: 60px; left: 300px;"></div>
<div class='other-object' style="top: 100px; left: 200px;"></div>
<div class='other-object' style="top: 200px; left: 100px;"></div>
</div>
CSS
.parent {
border: 1px solid black;
width: 100%;
height: 300px;
}
.object {
position: absolute;
background-color: red;
width: 50px;
height: 50px;
}
.other-object {
position: absolute;
background-color: blue;
width: 80px;
height: 80px;
}
.line {
position: absolute;
}
.line.vertical {
width: 0px;
height: 100%;
border-left: 1px dotted black;
}
.line.horizontal {
width: 100%;
height: 0px;
border-top: 1px dotted black;
}
JavaScript
$('.other-object').draggable({
containment: '.parent'
});
$('.object').draggable({
containment: '.parent',
snap: '.other-object',
snapTolerance: 5,
drag: function (event, ui) {
// You'll want to debounce this function so that it doesn't run every mouse move (e.g. see Ben Alman's site @ http://tinyurl.com/37dyjug)
var debounceTime = 200; // milliseconds
setTimeout(function () {
// Loop through all 'other-object's and see if we're lined up
$(".other-object").each(function (idx, other) {
var $other = $(other);
// Determine whether we're "close enough" to display the line
var padding = 1;
var closeToLeft = Math.abs($other.offset().left - ui.offset.left) < padding;
var closeToTop = Math.abs($other.offset().top - ui.offset.top) < padding;
// You can add closeToRight/closeToBottom, but you may need to do some calculation, e.g. right = left + width
// If we're close, display a line, otherwise remove that same line
// TODO: Find a better way of tagging which 'other-object' this line belongs to, using IDs or something more stable than the index of the jQuery each() function!
var id = 'leftOther' + idx;
if (closeToLeft) {
console.debug(idx, 'left');
$('.parent').not(':has(#' + id + ')').append('<div id="' + id + '" class="line vertical" style="left: ' + $other.offset().left + 'px;"/>');
} else {
$('#' + id).remove();
}
id = 'topOther' + idx;
if (closeToTop) {
console.debug(idx, 'top');
$('.parent').not(':has(#' + id + ')').append('<div id="topOther' + idx + '" class="line horizontal" style="top: ' + $other.offset().top + 'px;"/>');
} else {
...