Bug: Horizontal scrolling in UI Library on macOS duplicates UI elements


Hi! Trying out a trial of Balsamiq Mockups 3.5.5 on macOS Sierra (10.12.2) on a 2015 iMac with the Apple Magic Trackpad 2 (that’s a mouthful).

I noticed when choosing a category in the UI Library on top (“Assets”, “Big”, etc…) and scrolling through it with the trackpad, the scrollbar/elevator will get stuck all the way to the right, and then scrolling back and forth will start spamming the UI Library with duplicate elements (which gets worse the more you try scrolling). I’ve attached a picture of what I’m talking about:

This happens both when scrolling left/right on the trackpad, or using the “SHIFT+vertical scroll” trick. Interestingly enough, it does not seem to happen on the “All” list in the UI LIbrary, so I’ll be sticking with that for now. Hope this is reproducible - let me know if you need more information.



Oh wow, that’s no good, @Capm. I’m really sorry about that.

Does this happen with a blank project? Or just the project you are working on?

Something is triggering an RTE, and I’d love to see if we can figure out what it is! Let me know if you see it in every project, and we will start digging. :slight_smile:


Thanks for the reply @Brendan! I went to File > New Project, closed the other project and can reproduce the bug - it happens exactly the same. Let me know what else you need to know!


Ok, @Capm, that definitely sounds like an RTE. Once it breaks in one project, it probably breaks in all of them.

If you close out of Mockups completely (CMD + Q), and then reopen it, are you able to reproduce the bug in a fresh project?


@Brendan Yes - just closed all projects (CMD+W), closed the app (CMD+Q), and reopened it with a fresh project. Same bug is easy to reproduce just by scrolling left/right repeatedly with my trackpad. “Text Area” is the element that seems to clone itself the most, if that means anything.


Super weird, Jon.

Ok, what I’m going to do is loop Florian (one of our developers) in on this, and we are going to see if we can figure out what’s going on.

Florian is in the EU, so he is probably in bed right now, but I’ll have him look at this first thing in the morning.

Really sorry for the trouble, my friend. We will do everything we can to get it sorted.


Hi Jon and Brendan,

The multiple element issue is an old bug which we invested quite a bit of time on… I know it since Balsamiq Mockups 2.1.1? Back then I was a customer myself. :wink:

If you use the scrollbar at the bottom of the UI Library the issue does not occur.

The issue is the adobe list element that we use. The issue only occurs with fast right to left (and back) scrolling in the UI Library with a gesture. When you hit the maximum then it may happen that “another” element gets displayed.

We are in the process of dropping our Adobe dependencies. This version does not have the issue.


@Florian_Brauer Thanks very much for the update and explanation!

I did discover that grabbing the scrollbar/elevator and dragging it prevents the issue (instead of using the trackpad swipe), but it’s more convenient to stay on the “All” menu, where the glitch didn’t seem to happen, and continue using the trackpad swipe. I do want to note that the glitch happens for any speed scrolling back and forth with the trackpad - no matter fast or glacially slow.

Cool to know that the issue is known and being worked on! I look forward to seeing how performance is without the Adobe dependencies. Thanks again.