Render a virtual list of Clearwater components where list items outside of the visible area of the page are not rendered. They are inserted just in time while scrolling and removed when they are no longer visible.

Add this line to your application's Gemfile:

gem 'clearwater-virtual_list'

And then execute:

$ bundle

Or install it yourself as:

$ gem install clearwater-virtual_list

Inside your Clearwater app:

require 'clearwater/component'
require 'clearwater/virtual_list'

class MyList
  include Clearwater::Component
  
  def initialize(items: [], list_style:, item_style:)
    # VirtualList will give you the items to render within the viewport
    @items = items
    
    # Make sure you set your list container's style property to this value
    @list_style = list_style
    
    # Make sure the list items' styles are set with this
    @item_style = item_style
  end
  
  def render
    ul({ style: @list_style }, @items.map { |item|
      li({ style: @item_style }, [
        # ...
      ])
    })
  end
end

# Define the virtual list component in terms of your regular list component
MyVirtualList = Clearwater::VirtualList.create do |items:, list_style:, item_style:|
  MyList.new(
    items: items,
    list_style: list_style,
    item_style: item_style,
  )
end

Use the items and item_height keyword arguments to the component when using it:

class Layout
  include Clearwater::Component

  def render
    div([
      h1('My list of things'),
      MyVirtualList.new(
        items: all_the_things, # The full list of items
        item_height: 100,      # The height of each item in pixels
      ),
    ])
  end
end

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/clearwater-rb/clearwater-virtual_list. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the Clearwater::VirtualList project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.