Animate hiding contained borders

[leo@…]

Click on "go" on... ​http://jsfiddle.net/kG3dD/

Repro'd on jquery v1.5.1 and 1.4.2.

Two nested divs of the same size, with inner set to 100%. Inner div is yellow with a blue border. Animating the size of the outer div clips the bottom and right blue border during animation, and then restores them when done.

I'd expect the blue border to remain in tact during the animation. Maybe this is deliberate for some other reason, but the behavior certainly seems buggy.

[gnarf]

This bug doesn't surprise me much, ​http://jsfiddle.net/gnarf/kG3dD/1/

If you take a look at that fiddle, you'll see that the outer container is applied an overflow: hidden ... This causes the inside box to fall outside because width: 100% doesn't take into account the borders on the element.

See also ​http://jsfiddle.net/gnarf/kG3dD/3/ for a "working" version of your fiddle...

[leo@…]

In the simplified example, it's easy to do the math yourself on the boxes and make them fit. In the real world where this came from that doesn't work.

Adding .css('overflow', 'visible') after the .animate() call is a fairly good workaround, i.e. ​http://jsfiddle.net/q3j3R/

[gnarf]

You could also just use box-sizing: border-box where supported... ​https://developer.mozilla.org/en/CSS/box-sizing

[dmethvin]

We can't do anything about this, it's the default CSS box model. As gnarf says, you could use box-sizing: border-box when possible.