1402045 - Dropdown requires unusually high overhead

Status: RESOLVED DUPLICATE of bug 1118086

(Core :: Layout: Form Controls, defect)

Description

[support]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:55.0) Gecko/20100101 Firefox/55.0
Build ID: 20170824053622

Steps to reproduce:

Click a dropdown with many items.
Here's some sample code to build one for you:

<select id='dropdown'></select>


<script>
var dd = document.getElementById('dropdown');
for(var d=0; d<10000; d++){
	var day = new Date();
	day.setDate(day.getDate() - d);
	var option = document.createElement("option");
		option.text = day.toString();
		option.value = d;
	dd.add(option); 
}
</script>


Actual results:

Keep an eye on the CPU consumption and the performance of your browser when it's clicked. During a few tests, it rendered my install comatose. I could click tabs (they wouldn't focus), click refresh (it wouldn't reload). All i could do was force-quit.


Expected results:

I don't think the overhead required to expand a dropdown should have been quite so high.