width: auto incorrectly reverted to "auto" in extreme edge case

[paul-geonomics]

Hi,

the following bug can be reproduced in this fiddle: http://jsfiddle.net/pingless/48dub1LL/

When an element has a negative margin, and is flown in from beyond the side of the screen, velocity incorrectly sets the size to 'auto' after the animation.
This is visible when toggling the sidebar on, then off; when it moves out, the sidebar content gets "squished" when it should stay fixed-size (100%).

The problem is caused by lines 2601-2613: https://github.com/julianshapiro/velocity/blob/master/jquery.velocity.js#L2601
The element's size is set to auto, then the width is compared, to determine if the width was auto beforehand. In the case where there is a negative margin, it appears this calculation returns a false positive.

We're working around this problem by setting width: 100% !important on the element being animated (which overrides any values velocity might set), but this is not an ideal solution. I hope this can be fixed...

Hi Julian,
I've managed to reproduce it with positive margin: http://jsfiddle.net/pingless/48dub1LL/1/
It also reproduces with position: fixed: http://jsfiddle.net/pingless/48dub1LL/2/

I tried it with box-sizing: content-box but it seems that when calc() is used, you don't get the same width as auto (probably due to fractional pixel units, i.e. e.g. 350.2px looks the same as 350px but is not considered the same width).

Thanks,

Paul L

[julianshapiro]

Thank you for the detailed bug report, Paul. Looking into this now...

Okay, so updating my list from above. It's caused by the element having:

• a negative margin/left/top resulting in the element being partially hidden from view
• position: absolute/fixed
• animating to a px unit
• a width: 100% that resolves to the same value as width: auto during the beginning of the animation.

[julianshapiro]

I'm doing a drastic overhaul of Velocity's unit conversion logic. Performance will be degraded a tiny bit, but it'll result in being able to avoid placing all these arbitrary internal CSS values on element animated with Velocity. Expect an update early next week.

[julianshapiro]

Actually, Velocity just got significantly faster because I fixed a latent bug in the process. Yay!

[paul-geonomics]

Brilliant, thanks Julian!
Looking forward to the release.

[julianshapiro]

Please test and let me know if all is good :)