Good day,
I am using Scriptaculous' drag and drop library in my project and I find
that if I have more than 4 Droppables on a page that contains many nested
elements, the motion of any draggable seem to be bumpy instead of smooth.
This happens on IE only.
To see this in action, copy and paste this testcase into a file:
====
<html>
<script type="text/javascript" src="prototype.js"></script>
<script type="text/javascript" src="scriptaculous.js"></script>
<script type="text/javascript">
function init() {
new Draggable($("dd"));
Droppables.add($("pp"), {hoverclass:"over"});
Droppables.add($("pp2"), {hoverclass:"over"});
Droppables.add($("pp3"), {hoverclass:"over"});
Droppables.add($("pp4"), {hoverclass:"over"});
Droppables.add($("pp5"), {hoverclass:"over"});
}
</script>
<style type="text/css">
div {position:relative}
span {background:silver}
.over {background:gray}
</style>
<body onload="init();">
<div><div><div><div><div><div><div><div><div><div>
<p><span id="dd">draggable</span></p>
<p><span id="pp">drop</span></p>
<p><span id="pp2">drop</span></p>
<p><span id="pp3">drop</span></p>
<p><span id="pp4">drop</span></p>
<p><span id="pp5">drop</span></p>
</div></div></div></div></div></div></div></div></div></div>
</body>
</html>
====
After writing some unit tests, I discovered that Droppables was incurred a
bottleneck by having to calculate Position.cumulativeOffset for each
droppable on each mouseMove. Because the bumpy behavior was unacceptable to
our QA staff, I had to write some optimization code.
I achieved this by modifying Droppables.isAffected and Droppables.show to
use an implementation of Position.cumulativeOffset that caches the offset
values when a flag is set. The flag is set on a per droppable basis and is
used to hint to the implementation that the droppable has a static location
and therefore its position can be cached.
I was wondering if future Scriptaculous releases would benefit from such an
optimization.
Thank you for your time and you have yourself a nice day.
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