View Source Theming components
1-the-problem
1. The problem
The storybook allows you to apply different themes to your components. The selected theme is merged into the components assigns, which can then use it to apply matching styling rules.
While this is working great in the storybook, you probably don't want to pass in your application code the same theme assign to all your components.
2-store-the-theme-in-a-registry
2. Store the theme in a Registry
An effective way to store the current theme setting so that it can be available to all your components, but still have different examples for different (concurrent) users is to associate it to the current LiveView pid.
Registry
is a native Elixir module that handles decentralized storage, linked to specific
processes. We will leverage on this to associate a theme to the current LiveView pid.
First start a Registry
from your Application
module.
defmodule PhenixStorybook.Application do
def start(_type, _args) do
children = [
{Registry, keys: :duplicate, name: ThemeRegistry}
]
end
end
Then create a LiveView Hook that will fetch the theme from wherever it is relevant for your
application: database, user session, URL params... and store it in the Registry
(it's working
because the Hook is running under the same pid than the Liveview).
defmodule ThemeHook do
def on_mount(:default, params, _session, socket) do
theme = current_user_theme(socket, params)
Registry.register(ThemeRegistry, :theme, theme)
{:cont, socket}
end
end
Mount the hook in your router
.
defmodule Router do
live_session :default, on_mount: [ThemeHook] do
scope "/" do
# ...
end
end
end
3-fetch-the-theme-from-the-registry
3. Fetch the theme from the Registry
Write a helper module, to be used from your components to fetch the current theme from the
Registry
and merge it in the component's assigns.
defmodule ThemeHelpers do
def set_theme(assigns) do
pid_and_themes = Registry.lookup(ThemeRegistry, :theme)
case find_by_pid(pid_and_themes, self()) do
{_pid, theme} -> Map.put_new(assigns, :theme, theme)
_ -> raise("theme not found in registry")
end
end
defp find_by_pid(pid_and_themes, current_pid) do
Enum.find(pid_and_themes, fn {pid, _} -> pid == current_pid end)
end
end
4-css-theming
4. CSS theming
The storybook is applying a theme-*
CSS class to your components/page containers and you should do
as well to your application HTML body element.
It will allow you to style raw HTML elements
body.theme-colorful {
font-family: // ...
}
.theme-colorful h1 {
font-family: // ...
font-size: // ...
}