A set of key/value pairs representing measurements of various dimensions of an element.
Element.Layout class is a specialized way to measure elements.
It helps mitigate:
- The convoluted steps often needed to get common measurements for elements.
- The tendency of browsers to report measurements in non-pixel units.
- The quirks that lead some browsers to report inaccurate measurements.
- The difficulty of measuring elements that are hidden.
Element.Layout class by passing an element into the
var layout = new Element.Layout(someElement);
You can also use
Element.getLayout, if you prefer.
Once you have a layout object, retrieve properties using
layout.get('width'); //-> 400 layout.get('top'); //-> 180
The following are the CSS-related properties that can be retrieved.
Nearly all of them map directly to their property names in CSS. (The
only exception is for borders — e.g.,
border-width instead of
In addition, these "composite" properties can be retrieved:
padding-box-width(width of the content area, from the beginning of the left padding to the end of the right padding)
padding-box-height(height of the content area, from the beginning of the top padding to the end of the bottom padding)
border-box-width(width of the content area, from the outer edge of the left border to the outer edge of the right border)
border-box-height(height of the content area, from the outer edge of the top border to the outer edge of the bottom border)
margin-box-width(width of the content area, from the beginning of the left margin to the end of the right margin)
margin-box-height(height of the content area, from the beginning of the top margin to the end of the bottom margin)
Because these properties can be costly to retrieve,
behaves differently from an ordinary
First: by default, values are "lazy-loaded" — they aren't computed until they're retrieved. To measure all properties at once, pass a second argument into the constructor:
var layout = new Element.Layout(someElement, true);
Second: once a particular value is computed, it's cached. Asking for
the same property again will return the original value without
re-computation. This means that an instance of
becomes stale when the element's dimensions change. When this
happens, obtain a new instance.
Because it's a common case to want the dimensions of a hidden element
(e.g., for animations), it's possible to measure elements that are
However, it's only possible to measure a hidden element if its parent
is visible. If its parent (or any other ancestor) is hidden, any
width and height measurements will return
0, as will measurements for