Use Polymer.IronOverlayBehavior to implement an element that can be hidden or shown, and displays
on top of other content. It includes an optional backdrop, and can be used to implement a variety
of UI controls including dialogs and drop downs. Multiple overlays may be displayed at once.
See the demo source code for an example.
- Focus wrapping is not guaranteed to work for elements with
tabindex > 0, see more details here. Consider overriding_focusableNodesor using the Blocking Elements polyfill.
An overlay may be hidden by closing or canceling. The difference between close and cancel is user
intent. Closing generally implies that the user acknowledged the content on the overlay. By default,
it will cancel whenever the user taps outside it or presses the escape key. This behavior is
configurable with the no-cancel-on-esc-key and the no-cancel-on-outside-click properties.
close() should be called explicitly by the implementer when the user interacts with a control
in the overlay element. When the dialog is canceled, the overlay fires an 'iron-overlay-canceled'
event. Call preventDefault on this event to prevent the overlay from closing.
By default the element is sized and positioned to fit and centered inside the window. You can
position and size it manually using CSS. See Polymer.IronFitBehavior.
Set the with-backdrop attribute to display a backdrop behind the overlay. The backdrop is
appended to <body> and is of type <iron-overlay-backdrop>. See its doc page for styling
options.
In addition, with-backdrop will wrap the focus within the content in the light DOM.
Override the _focusableNodes getter
to achieve a different behavior.
The element is styled to appear on top of other content by setting its z-index property. You
must ensure no element has a stacking context with a higher z-index than its parent stacking
context. You should place this element as a child of <body> whenever possible.
iron-overlay-backdrop is a backdrop used by Polymer.IronOverlayBehavior. It should be a
singleton.
The following custom properties and mixins are available for styling.
| Custom property | Description | Default |
|---|---|---|
--iron-overlay-backdrop-background-color |
Backdrop background color | #000 |
--iron-overlay-backdrop-opacity |
Backdrop opacity | 0.6 |
--iron-overlay-backdrop |
Mixin applied to iron-overlay-backdrop. |
{} |
--iron-overlay-backdrop-opened |
Mixin applied to iron-overlay-backdrop when it is displayed |
{} |