# WebUI HelpBubble Implementation (Frontend)
[Backend documentation can be found here.](/components/user_education/webui/README.md)
Allows a WebUI page to support Polymer-based, blue material design ("Navi")
[HelpBubble](/components/user_education/common/help_bubble.h)s that can be shown in the course of a
[Feature Promo](/components/user_education/common/feature_promo_controller.h) or
[Tutorial](/components/user_education/common/tutorial.h).
This is done by associating HTML elements in a component with an
[ElementIdentifier](/ui/base/interaction/element_identifier.h) so they can be
referenced by a Tutorial step or a `FeaturePromoSpecification`.
Once elements are linked in this way, their visibility is reported via
[ElementTracker](/ui/base/interaction/element_tracker.h) and can be referenced
for any of the usual purposes (e.g. in tests or "hidden" Tutorial steps) and
not just for the purpose of anchoring a help bubble.
## Usage
Please start with the instructions in the
[Backend Usage Guide](/components/user_education/webui/README.md#usage), and
proceed here when you reach the appropriate step.
Once you have performed setup on the backend:
* Add [HelpBubbleMixin](./help_bubble_mixin.ts) to your Polymer component.
* In your component's `ready()` or `connectedCallback()` method, call
`HelpBubbleMixin.registerHelpBubbleIdentifier()` one or more times.
* The first parameter should be the name of an
[ElementIdentifier](/ui/base/interaction/element_identifier.h) you
specified when creating your
[HelpBubbleHandler](/components/user_education/webui/help_bubble_handler.h)
in your
[WebUIController](/content/public/browser/web_ui_controller.h)
* For elements declared with `DECLARE_ELEMENT_IDENTIFIER_VALUE()` this is
just the name of the constant you specified.
* The second parameter should be the HTML element id of the element you wish
to anchor the help bubble to when it is displayed.
* In this way, you effectively create a mapping between the native identifier
and the anchor element.
* You may add multiple mappings, though each ElementIdentifier name and each
HTML id may only be mapped once.
* You may also add mappings for elements you do not intend to anchor a help
bubble to, but whose visibility you care able for a Tutorial step or
interactive test.
* It is rare, but if your anchor element is not immediately present in your
component, you can instead wait to call `registerHelpBubbleIdentifier()`
until after the element is created.
## Limitations
Currently the frontend has the following limitations (many of these will be
relaxed or removed in the near future):
* Whether the native code believes that a help bubble can be shown in your
component is based on the visibility of the corresponding anchor HTML element
- the one with the ID you passed to
`HelpBubbleMixin.registerHelpBubbleIdentifier()`.
* Visibility is not determined relative to the current viewport but rather to
the entire page. The viewport will automatically scroll to display the
anchor element when the bubble is shown.
* Some features of `HelpBubble` are not yet supported (or are not fully
supported) in WebUI. Support for the following will be added in future
updates:
* Timeouts
* Close button
* Action buttons
* Progress indicator
* Most `user_education::HelpBubbleArrow` values
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