The overlay package provides a way to open floating panels on the screen.
Calling overlay.create() will return an OverlayRef instance. This instance is a handle for managing that specific overlay.
The OverlayRef is a PortalOutlet- once created, content can be added by attaching a Portal. See the documentation on portals for further information.
const overlayRef = overlay.create();
const userProfilePortal = new ComponentPortal(UserProfile);
overlayRef.attach(userProfilePortal);
When creating an overlay, an optional configuration object can be provided.
const overlayRef = overlay.create({
height: '400px',
width: '600px',
});
The full set of configuration options can be found in the API documentation.
The positionStrategy configuration option determines how the overlay will be positioned on-screen. There are two position strategies available as part of the library: GlobalPositionStrategy and ConnectedPositionStrategy.
GlobalPositionStrategy is used for overlays that require a specific position in the viewport, unrelated to other elements. This is commonly used for modal dialogs and application-level notifications.
ConnectedPositionStrategy is used for overlays that are positioned relative to some other "origin" element on the page. This is commonly used for menus, pickers, and tooltips. When using the connected strategy, a set of preferred positions is provided; the "best" position will be selected based on how well the overlay would fit within the viewport.
A custom position strategy can be created by implementing the PositionStrategy interface. Each PositionStrategy defines an apply method that is called whenever the overlay's position should be updated. A custom position strategy can additionally expose any other APIs necessary as related to the positioning of the overlay element.
The scrollStrategy configuration option determines how the overlay will react to scrolling outside the overlay element. There are four scroll strategies available as part of the library.
NoopScrollStrategy is the default option. This strategy does nothing.
CloseScrollStrategy will automatically close the overlay when scrolling occurs.
BlockScrollStrategy will block page scrolling while the overlay is open. Note that some applications may implement special or customized page scrolling; if the BlockScrollStrategy conflicts with this kind of situation, it can be overriden by re-providing BlockScrollStrategy with a custom implementation.
RepositionScrollStrategy will re-position the overlay element on scroll. Note that this will have some performance impact on scrolling- users should weigh this cost in the context of each specific application.
A custom scroll strategy can be created by implementing the ScrollStrategy interface. Each strategy will typically inject ScrollDispatcher (from @angular/cdk/scrolling) to be notified of when scrolling takes place. See the documentation for ScrollDispatcher for more information on how scroll events are detected and dispatched.
The OverlayContainer provides a handle to the container element in which all individual overlay elements are rendered. By default, the overlay container is appended directly to the document body so that an overlay is never clipped by an overflow: hidden parent.
The FullscreenOverlayContainer is an alternative to OverlayContainer that supports correct displaying of overlay elements in fullscreen mode.
FullscreenOverlayContainer can be enabled by providing it in your NgModule:
@NgModule({
providers: [{provide: OverlayContainer, useClass: FullscreenOverlayContainer}],
// ...
})
export class MyModule { }