896914 - css transition dont work if trasformed value has no value

Status: RESOLVED DUPLICATE of bug 571344

(Core :: CSS Parsing and Computation, defect)

Description

[uleming]

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:22.0) Gecko/20100101 Firefox/22.0 (Beta/Release)
Build ID: 20130618035212

Steps to reproduce:

very simple example with just a single div on page with class .box
.box{
    height: 0px;
    background-color: #c93838;
    transition: height 2s;
}

.boxIn{
    height: 500px;
}


page has script 
document.body.onload(function(){
var cClass = document.getElementByName('div')[0].className;
document.getElementByName('div')[0].className = cClass + ' .boxIn';
})


Actual results:

there is no transition if no initial value assigned to height of div element
.box{
    height: 0px;   <---- important (comment this line and transition will disappear)

height will jump from 0 to 500px
Same will happen even if div has some content


only way to make transition work, assign initial height of div 


Expected results:

I am not sure what will say w3c about this. I thought that if div has no initial value than it has value which calculated by firefox depends on content in it. 
Now transited element style should have some initial value mandatory, which could be unknown. For example in case above, content of div generated dynamically an unknown at moment of transition.

Comment 1

[Mardeg]

Moved to same component as bug 726550

Comment 2

[Boris Zbarsky [:bzbarsky]]

> I am not sure what will say w3c about this.

Per spec, there should be no transition here.