Clearing listboxes, very slow.

I've been using a few listboxes on my new project and was struggling with performance. At first I thought the problem was either filling the listbox with too many items, or the way I was filling them (from objects). For example, if I had 1000 objects and tried to put an attribute from each object into several listboxes, it seemed to take several seconds to fill.

However, I tried a new, very simple project and I noticed that the performance is actually very good except when clearing the listbox. If I clear 10 listboxes (with 100 items), it takes about 2.5 seconds to complete (the more items to clear, the slower it gets, it's not noticeable with the 3 initial items). Filling the listboxes with 100 items only takes about 0.025 seconds. Even doing a fairly complex fill is very fast, it's just clearing the boxes which is so slow.

Is this to be expected and is there anything that I can do to speed things up a bit?

I tried it out - it's way slower in Chrome then Firefox. Looking at the code it removes each element one at a time so it's not surprising. Clearing the lists in one go with JavaScript is faster. It's instant in Chrome with 10 lists of 1000 items each. Still a bit slow in Firefox but faster than the clear action.

clearLists.capx (r200)

Wow, thanks dude. I was thinking I might have to abandon the listboxes and use something else but perhaps this is doable after all

Perhaps something for Ashley and co to look at? I know listboxes aren't crucial to most games but it shouldn't be a huge job. Or does the browser do all the work, so it's not a C2 issue?

One thing I've noticed on my mobile is that when I select an item in a listbox, and then select another listbox, both boxes remain highlighted with a blue background. In fact, if I select an item in all 10 boxes, they all remain highlighted. I don't know how to turn this highlighting off. Unfocusing the box doesn't work, nor setting the selected item to an odd number (e.g -1). I thought it might be just on IE since my mobile uses IE but it doesn't do that in IE on my PC. Any ideas how to unhighlight the listbox text?

You're right, it is slow. I've fixed it to use the faster workaround for the next beta. (I was going by ramones's .capx, it is always a good idea to provide your own .capx if you think something is slow to prove your point.)

Thanks Ashley. I did have my own capx to demonstrate it, but Ramones beat me to it while I was trying to work out how to upload it - besides, his is better