**[ This description is mirrored from README.md at [github.com/BrightspaceUI/hierarchical-view](https://github.com//BrightspaceUI/hierarchical-view/blob/v2.4.0/README.md) on 2019-05-10 ]**
# d2l-hierarchical-view
[](https://www.webcomponents.org/element/BrightspaceUI/hierarchical-view)
[![Bower version][bower-image]][bower-url]
[![Build status][ci-image]][ci-url]
A [Polymer](https://www.polymer-project.org/1.0/)-based web component and behavior for hierarchical views.
## Installation
`d2l-hierarchical-view` can be installed from [Bower][bower-url]:
```shell
bower install d2l-hierarchical-view
```
## Usage
Include the [webcomponents.js](http://webcomponents.org/polyfills/) "lite" polyfill (for browsers who don't natively support web components), then import the component or behavior.
### Component
#### HTML
```html
```
Nest the `d2l-hierarchical-view` elements on your page.
```html
view 1
min-height: 200
view 2a
min-height: 400
view 3
min-height: 300
view 2b
min-height: 200
```
#### Methods
Use the `show` and `hide` methods on child views to control visibility:
```javascript
// to show child (hiding parent)
child.show();
// to hide child (show parent)
child.hide();
```
Other helpful methods:
```javascript
// get the currently active hierarchical view
view.getActiveView();
// get the root hierarchical view
view.getRootView();
// whether the specified hierarchical view is the active view
view.isActive();
// force resize of the hierarchical view (useful if initially not displayed when attached)
view.resize();
```
#### Events
The hierarchical views raise show/hide events when showing or hiding child views.
```javascript
// triggered when child view will be shown (before animation begins)
view.addEventListener('d2l-hierarchical-view-show-start', () => { ... });
// triggered when child view is shown (when animation ends)
view.addEventListener('d2l-hierarchical-view-show-complete', () => { ... });
// triggered when child view will be hidden (before animation begins)
view.addEventListener('d2l-hierarchical-view-hide-start', () => { ... });
// triggered when child view is hidden (when animation ends)
view.addEventListener('d2l-hierarchical-view-hide-complete', () => { ... });
```
### Behavior
To implement a custom hierarchical view component, import the `d2l-hierarchical-view-behavior.html` behavior, include the `d2l-hierarchical-view-styles` styles, and define a template containing the `d2l-hierarchical-view-content` class. For example, see [d2l-hierarchical-view](https://github.com/Brightspace/d2l-hierarchical-view-ui/blob/master/d2l-hierarchical-view.html).
## Developing, Testing and Contributing
After cloning the repo, run `npm install` to install dependencies.
If you don't have it already, install the [Polymer CLI](https://www.polymer-project.org/2.0/docs/tools/polymer-cli) globally:
```shell
npm install -g polymer-cli
```
To start a [local web server](https://www.polymer-project.org/2.0/docs/tools/polymer-cli-commands#serve) that hosts the demo page and tests:
```shell
polymer serve
```
To lint ([eslint](http://eslint.org/) and [Polymer lint](https://www.polymer-project.org/2.0/docs/tools/polymer-cli-commands#lint)):
```shell
npm run lint
```
To run unit tests locally using [Polymer test](https://www.polymer-project.org/2.0/docs/tools/polymer-cli-commands#tests):
```shell
polymer test --skip-plugin sauce
```
To lint AND run local unit tests:
```shell
npm test
```
[bower-url]: http://bower.io/search/?q=d2l-hierarchical-view
[bower-image]: https://badge.fury.io/bo/d2l-hierarchical-view.svg
[ci-url]: https://travis-ci.org/BrightspaceUI/hierarchical-view
[ci-image]: https://travis-ci.org/BrightspaceUI/hierarchical-view.svg?branch=master
## Versioning
Commits and PR merges to master will automatically do a minor version bump which will:
* Update the version in `package.json`
* Add a tag matching the new version
* Create a github release matching the new version
By using either **[increment major]** or **[increment patch]** notation inside your merge message, you can overwrite the default version upgrade of minor to the position of your choice.
