Protos

A UI component library for Phlex using tailwindcss and daisyUI.

You can see a full list of the components at https://protos.inhouse.work/.

• Tailwindcss classes are merged using tailwind_merge.
• Uses tippy.js for dropdowns, combobox, and popovers
• All components avoid using Phlex::DeferredRender so you can reorder components exactly how you like them.

Other Phlex based UI libraries worth checking out:

• PhlexUI
• ZestUI

Thinking of making your next static site using Phlex? Check out staticky. The protos docs were published using it.

Phlex components

Phlex is a fantastic framework for building frontend components in pure Ruby:

class Navbar
  def view_template
    header(class: "flex items-center justify-between") do
      h3 { "My site" }
      button { "Log out" }
    end
  end
end

But how can we sometimes render this Navbar with a different background color?

It would be nice to have our components take a class like any other element:

render Navbar.new(class: "bg-primary")

Unfortunately class is a special keyword in Ruby, so we need to do some awkward handling to use it like this:

class Navbar
  def initialize(**options)
    # Keyword `class` is a special word in Ruby so we have to awkwardly unwrap
    # like this instead of using keyword arguments
    @classes = options[:class]
  end

  def view_template
    header(class: "#{@classes} flex items-center justify-between") do
      h3 { "My site" }
      button { "Log out" }
    end
  end
end

Now we can pass in a style to our container, but what about overriding the style of the h3 tag?

class Navbar
  def initialize(**options)
    # Keyword `class` is a special word in Ruby so we have to awkwardly unwrap
    # like this instead of using keyword arguments
    @container_classes = options[:class]
    @title_classes = options[:title_class]
  end

  def view_template
    header(class: "#{@classes} flex items-center justify-between") do
      h3(class: @title_classes) { "My site" }
      button { "Log out" }
    end
  end
end

Eventually everyone makes a kind of ad-hoc system for specifying styles. It gets more complicated when you have attributes like a data-controller. How do you give a good experience letting people using your components to add their own controllers while your component depends on one already?

This library is an attempt to make this kind of developer experience while making reusable components more convention over configuration.

Protos::Component

A protos component follows 3 conventions that make them easy to work with as components in your app:

• Slots and themes
• Attrs and default attrs
• Params and options

Every UI component library will have a tension between being too general to fit in your app or too narrow to be useful. Making components that look good out of the box can make them hard to customize.

We try and resolve this tension by making these components have a minimal style that can be easily overridden using some ergonomic conventions.

Slots and themes

Components are styled with css slots that get their values from a simple hash we call a theme.

You define a theme for your component by defining a #theme method that returns a hash.

Users of your components can override, merge, or remove parts of your theme by passing in their own as an argument to the component. Another nice benefit is that your markup doesn't get overwhelmed horizontally with your css classes.

class List < Protos::Component
  def view_template
    ul(class: css[:list]) do
      li(class: css[:item]) { "Item 1" }
      li(class: css[:item]) { "Item 2" }
    end
  end

  def theme
    {
      list: ["space-y-4"], # We can use arrays
      item: "font-bold text-2xl" # Or just plain old strings
    }
  end
end

Using a theme and css slots allows us to easily override any part of a component when we render.

Here we are passing in our own theme. The default behavior is to add these styles on to the theme, rather than replacing them.

render List.new(
  theme: {
    list: "space-y-8",
    item: "bg-red-500"
  }
)

When the component is rendered the tailwind_merge gem will also prune any duplicate unneeded styles.

For example even though the themes list key would be added together to become space-y-4 space-y-8, the tailwind_merge gem will prune it down to just space-y-8 as the two styles conflict.

<ul class="space-y-8">
  <li class="font-bold text-2xl bg-red-500">Item 1</li>
  <li class="font-bold text-2xl bg-red-500">Item 2</li>
</ul>

We can override the slot entirely by using a ! at the end of the key:

render List.new(
  theme: {
    item!: "bg-red-500"
  }
)

The css slot css[:item] would be overridden rather than merged:

<li class="bg-red-500">Item 1</li>

We can also negate a certain class or classes from the slot by putting a ! at the start of the key:

render List.new(
  theme: {
    "!item": "text-2xl"
  }
)

The new css[:item] slot would be:

<li class="font-bold">Item 1</li>

If you want to change the method we define our default theme under you can override the theme_method on the class:

class List < Protos::Component
  theme_method :custom_theme

  # ...

  private

  def custom_theme
    {
      list: "space-y-4",
      item: ["font-bold", "text-2xl"]
    }
  end
end

Attrs and default attrs

By convention, all components spread in an attrs hash on their outermost element of the component. There is no rule for this, but it makes them feel more naturally like native html elements when you render them.

By doing this we enable 3 main conveniences:

1. We can pass a class keyword when initializing the component which will be merged safely into the css[:container] slot
2. We can pass any html attributes we want to the element such as id, data etc and it will just work
3. We can add default attributes that are safely merged with any provided to the component when its being initialized

class List < Protos::Component
  def view_template
    ul(**attrs) do
      # ...
    end
  end

  private

  def default_attrs
    {
        data: { controller: "list" }
    }
  end

  def theme
    {
      container: "space-y-4",
      item: "font-bold"
    }
  end
end

#attrs returns a hash which will by default merge the class keyword into the css[:container] slot which we define in our theme. The ul elements class would be space-y-4 as that is the css[:container] on our theme.

Special html options (class, data) will be safely merged.

For examples, the component above defines a list controller. If we passed our own controller into data when we initialize, the component's data-controller attribute would be appended to:

render List.new(
  data: { controller: "tooltip" }
)

That would output both controllers to the DOM element:

<ul data-controller="list tooltip">

This makes it very convenient to add functionality to basic components without overriding their core behavior or having to modify/override their class.

If we wanted to, just like for our theme we can change the method from default_attrs by defining the default_attrs_method on the class:

class List < Protos::Component
  default_attrs_method :custom_attrs

  private

  def custom_attrs
    {
      data: { controller: "list" }
    }
  end
end

Params and options

Components extend Dry::Initializer which lets us easily add new positional arguments with param or keyword arguments with option

class List < Protos::Component
  option :ordered
end

This makes our initialization declarative and easy to extend without having to consider how to call super in the initializer.

The following keywords are reserved in the base class:

• class
• theme
• html_options

You are free to add whatever positional or keyword arguments you like as long as they don't directly conflict with those names.

Putting it all together

Lets revisit the example of our Navbar component:

require "protos"

class Navbar < Protos::Component
  def view_template
    header(**attrs) do
      h1(class: css[:heading]) { "Hello world" }
      h2(class: css[:subtitle]) { "With a subtitle" }
    end
  end

  private

  def default_attrs
    {
      data: { controller: "navbar" }
    }
  end

  def theme
    {
      container: "flex justify-between items-center gap-sm",
      heading: "text-2xl font-bold",
      subtitle: "text-sm"
    }
  end
end

Now all the concerns about adding in our behavior, styles, etc are handled for us by convention:

render Navbar.new(
  # This will add to the component's css[:container] slot
  class: "my-sm",
  # This will add the controller and not remove
  # the existing one
  data: { controller: "counter" },
  theme: {
    heading: "p-sm",       # We can add tokens
    "!container": "gap-sm" # We can negate (remove) certain tokens
    subtitle!: "text-xl"   # We can override the entire slot
  }
)

Which produces the following html:

<header data-controller="navbar counter" class="flex justify-between items-center my-sm">
  <h1 class="text-2xl font-bold p-sm">Hello world</h1>
  <h2 class="text-xl">With a subtitle</h2>
</header>

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add protos

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install protos

Usage

Setup TailwindCSS, DaisyUI and add the protos path to your content.

npm install -D tailwindcss postcss autoprefixer daisyui
npx tailwindcss init

Then we need to add the protos path to the content of our tailwind config so tailwind will read the styles defined in the Protos gem.

Protos also uses semantic spacing such as p-sm or m-md instead of set numbers so you can easily choose the spacing you want. So we will need to extend spacing in your theme.

// tailwind.config.js
// For importing tailwind styles from protos gem
const execSync = require('child_process').execSync;
const outputProtos = execSync('bundle show protos', { encoding: 'utf-8' });
const protos_path = outputProtos.trim() + '/**/*.rb';

module.exports = {
  content: [
    "./app/views/**/*.{rb,html,html.erb,erb}",
    protos_path
  ],
  theme: {
    extend: {
      spacing: {
        xs: "var(--spacing-xs)",
        sm: "var(--spacing-sm)",
        md: "var(--spacing-md)",
        lg: "var(--spacing-lg)",
        xl: "var(--spacing-xl)",
      },
    },
  }
  // ....
}

Add protos-stimulus to your packages:

npm install protos-stimulus

And somewhere in your entrypoints import as a side effect:

import "protos-stimulus"

Then you can use the components in your apps.

Protos::Card.new(class: "bg-base-100") do |card|
  card.body(class: "gap-sm") do
    card.title(class: "font-bold") { "Hello world" }
    span { "This is some more content" }
    card.actions do
      button(class: "btn btn-primary") { "Action 1" }
    end
  end
end

Building your own components

You can override components simply by redefining sub-classing the class in your own app:

module Components
  class Swap < Protos::Component
    private

    def on(...)
      MyOnButton.new(...)
    end

    def theme
      super.merge({
        input: ["block", "bg-red-500"]
      })
    end
  end
end

But its much better to avoid the sub-classing and just render the component inside of your own:

module Components
  class Swap < ApplicationComponent
    def view_template
      render Protos::Swap.new do |c|
        # ....
      end
    end
  end
end

You could use Proto::List to create your own list and even use Phlex::DeferredRender to make the API more convenient.

Let's create a list component with headers and actions:

module Ui
  class List < Protos::Component
    include Protos::Typography
    include Phlex::DeferredRender

    option :title, default: -> {}
    option :ordered, default: -> { false }
    option :items, default: -> { [] }, reader: false
    option :actions, default: -> { [] }, reader: false

    def template
      article(**attrs) do
        header class: css[:header] do
          h3(size: :md) { title }
          nav(class: css[:actions]) do
            @actions.each do |action|
              render action
            end
          end
        end

        render Protos::List.new(ordered:, class: css[:list]) do
          @items.each { |item| render item }
          li(&@empty) if @items.empty?
        end
      end
    end

    def with_item(*, **, &block)
      theme = { container: css[:item] }
      @items << Protos::List::Item.new(*, theme:, **, &block)
    end

    def with_action(&block)
      @actions << block
    end

    def with_empty(&block)
      @empty = block
    end

    private

    def theme
      {
        container: "space-y-xs",
        header: "flex justify-between items-end gap-sm",
        list: "divide-y border w-full",
        actions: "space-x-xs",
        item: "p-sm"
      }
    end
  end
end

Now the component is specific to our application, and the styles are still overridable at all levels:

render Ui::List.new(title: "Project Names", ordered: true) do |list|
  list.with_action { link_to("Add item", "#") }
  list.with_item(class: "active") { "Project 1" }
  list.with_item { "Project 2" }
  list.with_item { "Project 3" }
end

Or here is another example of a table:

module Ui
  class Table < ApplicationComponent
    include Protos::Typography
    include Phlex::DeferredRender
    include Actionable

    class Column
      attr_reader :title

      def initialize(title, &block)
        @title = title
        @block = block
      end

      def call(item)
        @block.call(item)
      end
    end

    option :title, default: -> {}
    option :collection, default: -> { [] }, reader: false
    option :columns, default: -> { [] }, reader: false

    def template
      article(**attrs) do
        header class: css[:header] do
          h3(size: :md) { title } if title.present?
          nav(class: css[:actions]) do
            @actions.each do |action|
              render action
            end
          end
        end

        render Protos::Table.new(class: css[:table]) do |table|
          render(table.caption(class: css[:caption]), &@caption) if @caption
          render table.header do
            render table.row do
              @columns.each do |column|
                render table.head do
                  plain(column.title)
                end
              end
            end
          end

          render table.body do
            @collection.each do |item|
              render table.row do
                @columns.each do |column|
                  render table.cell do
                    column.call(item)
                  end
                end
              end
            end

            if @collection.empty?
              render table.row do
                render table.cell(colspan: @columns.length) do
                  @empty&.call
                end
              end
            end
          end
        end
      end
    end

    def with_column(...)
      @columns << Column.new(...)
    end

    def with_empty(&block)
      @empty = block
    end

    def with_caption(&block)
      @caption = block
    end

    def with_action(&block)
      @actions << block
    end

    private

    def theme
      {
        container: "space-y-sm",
        header: "flex justify-between items-end gap-sm",
        table: "border",
        caption: "text-muted"
      }
    end
  end
end

Which lets you have a very nice table builder:

collection = [
  {
    name: "John Doe",
    status: "Active",
    location: "New York"
  }
]

render Ui::Table.new(title: "A table", collection:) do |table|
  table.with_caption { "Users" }
  table.with_action do
    a(href: "#") { "Add new" }
  end

  table.with_column("Name") { |row| row[:name] }
  table.with_column("Location") { |row| row[:location] }
  table.with_column("Status") do |row|
    span(class: "badge badge-info") { row[:status] }
  end
  table.with_column("Actions") do
    a(href: "#") { "View" }
  end
end

Missing components

This library tries to avoid re-making Protos components for extremely simple DaisyUI components. Here is a list that we don't yet have components for:

• Buttons
• Checkbox
• File input
• Indicator
• Join
• Kbd
• Link
• Loading
• Mask
• Progress
• Radial progress
• Radio
• Range
• Select
• Skeleton
• Stack
• Text input
• Textarea
• Toggle
• Tooltip

Development

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 the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/inhouse-work/protos.

Benchmarks

You can run the benchmarks using the raketasks, e.g:

• bin/rake benchmark:ips:table
• bin/rake benchmark:memory:table
• bin/rake benchmark:ips:theme
• bin/rake benchmark:ips:attributes

There are also tasks for profiling and exploring memory consumption.

You can find the latest benchmarks in benchmarks/. These were run on a new Macbook M3 Pro chip.

Currently this library is 30x slower than plain Phlex components. This is due to the overhead of themes, attributes and other quality of life improvements.

This may seem like a lot but Phlex is so fast that rendering a large table can still be done 4000 times per second with this lib.

License

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