Element.Properties.opacity.get retrieves opacity from element's storage and not necessarily current opacity

[Devign]

Element.Properties.opacity.get retrieves opacity from storage, and unlike getComputedStyle it cannot retrieve current opacity unless set by Element.Properties.opacity.set.

Could it always read from style like getComputedStyle does?

Code example:

if (Browser.Engine.trident) return this.filters.alpha ? this.filters.alpha.opacity : 1
else return +this.getComputedStyle("opacity") || 1;

Thanks

[tomocchino]

In order to avoid browser inconsistencies you should always set opacity using MooTools... in this sense, the opacity accessor is only for use with elements that have had their opacity set by MooTools

[Devign]

But sometimes I have it my CSS, so when the page is loaded elements should be semi transparent. Setting opacity when dom is ready can cause a flicker.
In all modern browsers the following will work (filter/zoom for IE, opecity for the rest).

div {
	opacity:.4;
	filter:alpha(opacity=40);
	zoom:1;
	background-color:#669CB9;
}

[tomocchino]

Then for now i would suggest setting it in your CSS, and then using the setter to set it to the same value after the dom is ready. The patch will not be added before the 1.2 release, but we may look into it for 1.3.