docs(theming): clarify how nuxt ui augments tailwind config

docs/content/1.getting-started/3.theming.md

@@ -1,31 +1,57 @@
 ---
+title: Theming
 description: 'Learn how to customize the look and feel of the components.'
 ---
 
-This module relies on Nuxt [App Config](https://nuxt.com/docs/guide/directory-structure/app-config#app-config-file) file to customize the look and feel of the components at runtime with HMR (hot-module-replacement).
+## Overview
+
+Nuxt UI uses [Tailwind CSS](https://tailwindcss.com) to style its components and drive its color theme.
+
+You'll use two main files to modify the defaults:
+
+- [`app.config.ts`](https://nuxt.com/docs/guide/directory-structure/app-config#app-config-file) to specify the main theme colors and override component styles
+- [`tailwind.config.ts`](https://nuxt.com/docs/guide/directory-structure/app-config#app-config-file) to configure individual colors and palettes
 
 ## Colors
 
 ### Configuration
 
-Components are based on a `primary` and a `gray` color. You can change them in your `app.config.ts`.
+Nuxt UI's theme is configured using `primary` and `gray` color palettes:
+
+- `primary` is used for things like primary actions, accents, etc
+- `gray` is used for things like secondary actions, text, borders, etc
+
+Both these values indicate [named Tailwind colors](https://tailwindcss.com/docs/customizing-colors).
+
+You can specify these values in your [`app.config.ts`](https://nuxt.com/docs/guide/directory-structure/app-config#app-config-file)  file, under the  `ui` key:
 
 ```ts [app.config.ts]
 export default defineAppConfig({
   ui: {
+    // these are the Nuxt UI defaults
     primary: 'green',
-    gray: 'cool'
+    gray: 'gray'
   }
 })
 ```
 
+You options are:
+
+- skip config and accept the defaults, i.e. `green` and `grey`
+- choose any other Tailwind color, i.e. `rose` and `neutral`
+- choose nested colors, i.e. `brand.primary` and `brand.secondary`
+- override default or create custom colors (see [Customisation](#customisation) below)
+
 ::callout{icon="i-heroicons-light-bulb"}
-Try to change the `primary` and `gray` colors by clicking on the :u-icon{name="i-heroicons-swatch-20-solid" class="w-4 h-4 align-middle text-primary-500 dark:text-primary-400"} button in the header.
+Click the :u-icon{name="i-heroicons-swatch-20-solid" class="w-4 h-4 align-middle text-primary-500 dark:text-primary-400"} button in the header to try out other Tailwind colors!
+
 ::
 
-As this module uses Tailwind CSS under the hood, you can use any of the [Tailwind CSS colors](https://tailwindcss.com/docs/customizing-colors#color-palette-reference) or your own custom colors or groups, such as `brand.primary`. By default, the `primary` color is `green` and the `gray` color is `cool`.
+### Customisation
 
-When [using custom colors](https://tailwindcss.com/docs/customizing-colors#using-custom-colors) or [adding additional colors](https://tailwindcss.com/docs/customizing-colors#adding-additional-colors) through the `extend` key in your `tailwind.config.ts`, you'll need to make sure to define all the shades from `50` to `950` as most of them are used in the components config defined in [`ui.config/`](https://github.com/nuxt/ui/tree/dev/src/runtime/ui.config) directory. You can [generate your colors](https://tailwindcss.com/docs/customizing-colors#generating-colors) using tools such as https://uicolors.app/ for example.
+To use custom shades, you'll need a [tailwind.config.ts](https://tailwindcss.com/docs/installation) to [replace](https://tailwindcss.com/docs/customizing-colors#using-custom-colors) or [extend](https://tailwindcss.com/docs/customizing-colors#adding-additional-colors) the defaults.
+
+In the following example, we extend the default `green` config with a richer hue:
 
 ```ts [tailwind.config.ts]
 import type { Config } from 'tailwindcss'
@@ -54,23 +80,74 @@ export default <Partial<Config>>{
 }
 ```
 
-### CSS Variables
+Colors must supply all values from `50` to `950` because the Nuxt UI components use the full range.
 
-To provide dynamic colors that can be changed at runtime, this module uses CSS variables. As Tailwind CSS already has a `gray` color, the module automatically renames it to `cool` to avoid conflicts (`coolGray` was renamed to `gray` when Tailwind CSS v3.0 was released).
+If you need help in creating the colors, consider an online tools such as [UI Colors](https://uicolors.app).
 
-Likewise, you can't define a `primary` color in your `tailwind.config.ts` as it would conflict with the `primary` color defined by the module.
+You can peek at Nuxt UI's classes and values in the `ui.config` folder:
 
-::callout{icon="i-heroicons-light-bulb"}
-We'd advise you to use those colors in your components and pages, e.g. `text-primary-500 dark:text-primary-400`, `bg-gray-100 dark:bg-gray-900`, etc. so your app automatically adapts when changing your `app.config.ts`.
-::
+- on GitHub: [`runtime/ui.config/**/*.ts`](https://github.com/search?q=repo%3Anuxt%2Fui+path%3A%2F%5Esrc%5C%2Fruntime%5C%2Fui%5C.config%5C%2F%2F+-primary&type=code)
+- in your project: `node_modules/@nuxt/ui/dist/runtime/ui.config/**/*.mjs`
+
+### Usage
+
+You are encouraged to use these new  `primary-*` and `gray-*` classes in your pages and components so that when you [choose a new theme](#configuration) color, your whole design updates.
+
+Note that the `primary` color has a [default](https://tailwindcss.com/docs/customizing-colors#color-object-syntax) shade which lets you specify a color without a modifier:
+
+```vue
+<div class="text-primary focus-inside:ring-primary` />
+```
 
-The `primary` color also has a `DEFAULT` shade that changes based on the theme. It is `500` in light mode and `400` in dark mode. You can use as a shortcut in your components and pages, e.g. `text-primary`, `bg-primary`, `focus-visible:ring-primary`, etc.
+Additionally, it is adjusted based on the color scheme (`500` in light mode and `400` in dark mode).
+
+### How it works
+
+To support a range of tints for `primary` and `grey` Nuxt UI takes several steps:
+
+1. it renders the chosen theme color values into `:root`-level CSS variables
+2. it augments your Tailwind config with two new color config template blocks
+3. each template [combines](https://tailwindcss.com/docs/customizing-colors#using-css-variables) the CSS variables with alpha transparency placeholders
+
+The augmented (and [virtual](https://tailwindcss.nuxtjs.org/getting-started/configuration#exposeconfig)) Tailwind configuration looks something like this:
+
+```js
+{
+  primary: {
+    50: 'rgb(var(--color-primary-50) / <alpha-value>)',
+    100: 'rgb(var(--color-primary-100) / <alpha-value>)',
+    200: 'rgb(var(--color-primary-200) / <alpha-value>)',
+    ...
+  },
+  gray: {
+    50: 'rgb(var(--color-gray-50) / <alpha-value>)',
+    100: 'rgb(var(--color-gray-100) / <alpha-value>)',
+    200: 'rgb(var(--color-gray-200) / <alpha-value>)',
+    ...
+  }}
+```
+
+The end-result is that a class like `bg-primary-500/30` will be compiled by Tailwind to:
+
+```css 
+.bg-primary-500\/30 {
+  color: rgb(var(--color-primary-500) / 0.3);
+}
+```
+
+This is what allows Nuxt UI to show subtle variations on things like focus rings, borders, etc.
+
+::callout{icon="i-heroicons-bell-alert"}
+
+Note that [before Nuxt UI 2.19.0](https://github.com/nuxt/ui/blob/dev/docs/content/1.getting-started/3.theming.md#css-variables) the color key names `primary` and `gray` were reserved, but a recent update allows configuring these keys and the values will passed straight through as the theme's colors.
+
+::
 
 ### Smart Safelisting
 
 Components having a `color` prop like [Avatar](/components/avatar#chip), [Badge](/components/badge#style), [Button](/components/button#style), [Input](/components/input#style) (inherited in [Select](/components/select) and [SelectMenu](/components/select-menu)), [RadioGroup](/components/radio-group), [Checkbox](/components/checkbox), [Toggle](/components/toggle), [Range](/components/range) and [Notification](/components/notification#timeout) will use the `primary` color by default but will handle all the colors defined in your `tailwind.config.ts` or the default Tailwind CSS colors.
 
-Variant classes of those components are defined with a syntax like `bg-{color}-500 dark:bg-{color}-400` so they can be used with any color. However, this means that Tailwind will not find those classes and therefore will not generate the corresponding CSS.
+Variant classes of those components are defined with a syntax like `bg-{color}-500` or `dark:bg-{color}-400` so they can be used with any color. However, this means that Tailwind will not find those classes and therefore will not generate the corresponding CSS.
 
 The module uses the [Tailwind CSS safelist](https://tailwindcss.com/docs/content-configuration#safelisting-classes) feature to force the generation of all the classes for the `primary` color **only** as it is the default color for all the components.
 

src/runtime/plugins/colors.ts

@@ -1,21 +1,29 @@
 import { computed } from 'vue'
 import { get, hexToRgb } from '../utils'
-import { defineNuxtPlugin, useAppConfig, useNuxtApp, useHead } from '#imports'
+import { defineNuxtPlugin, useAppConfig, useHead, useNuxtApp } from '#imports'
 import colors from '#tailwind-config/theme/colors'
 
 export default defineNuxtPlugin(() => {
   const appConfig = useAppConfig()
   const nuxtApp = useNuxtApp()
 
   const root = computed(() => {
-    const primary: Record<string, string> | undefined = get(colors, appConfig.ui.primary)
-    const gray: Record<string, string> | undefined = get(colors, appConfig.ui.gray)
+    const ui = appConfig.ui
+    const keyPrimary = '$primary' in colors && ui.primary === 'primary'
+      ? '$primary'
+      : ui.primary
+    const keyGray = '$gray' in colors && ui.gray === 'gray'
+      ? '$gray'
+      : ui.gray
+
+    const primary: Record<string, string> | undefined = get(colors, keyPrimary)
+    const gray: Record<string, string> | undefined = get(colors, keyGray)
 
     if (!primary) {
-      console.warn(`[@nuxt/ui] Primary color '${appConfig.ui.primary}' not found in Tailwind config`)
+      console.warn(`[@nuxt/ui] Primary color '${ui.primary}' not found in Tailwind config`)
     }
     if (!gray) {
-      console.warn(`[@nuxt/ui] Gray color '${appConfig.ui.gray}' not found in Tailwind config`)
+      console.warn(`[@nuxt/ui] Gray color '${ui.gray}' not found in Tailwind config`)
     }
 
     return `:root {

src/runtime/utils/colors.ts

@@ -233,8 +233,18 @@ export const setGlobalColors = (theme: TWConfig['theme']) => {
     ...theme.extend?.colors
   }
 
-  // @ts-ignore
-  globalColors.primary = theme.extend.colors.primary = {
+  // reference theme as any
+  const themeColors: any = theme.extend.colors
+
+  // track user colors
+  const userColors: ColorConfig = {}
+
+  // primary colors
+  if (globalColors.primary) {
+    userColors.$primary = themeColors.$primary = globalColors.primary
+  }
+
+  globalColors.primary = themeColors.primary = {
     50: 'rgb(var(--color-primary-50) / <alpha-value>)',
     100: 'rgb(var(--color-primary-100) / <alpha-value>)',
     200: 'rgb(var(--color-primary-200) / <alpha-value>)',
@@ -250,13 +260,11 @@ export const setGlobalColors = (theme: TWConfig['theme']) => {
   }
 
   if (globalColors.gray) {
-    // @ts-ignore
-    globalColors.cool = theme.extend.colors.cool =
-      defaultColors.gray
+    userColors.$gray = themeColors.$gray = globalColors.gray
+    globalColors.cool = themeColors.cool = defaultColors.gray
   }
 
-  // @ts-ignore
-  globalColors.gray = theme.extend.colors.gray = {
+  globalColors.gray = themeColors.gray = {
     50: 'rgb(var(--color-gray-50) / <alpha-value>)',
     100: 'rgb(var(--color-gray-100) / <alpha-value>)',
     200: 'rgb(var(--color-gray-200) / <alpha-value>)',
@@ -270,7 +278,10 @@ export const setGlobalColors = (theme: TWConfig['theme']) => {
     950: 'rgb(var(--color-gray-950) / <alpha-value>)'
   }
 
-  return excludeColors(globalColors)
+  return [
+    ...excludeColors(globalColors),
+    ...Object.keys(userColors)
+  ]
 }
 
 export const generateSafelist = (colors: string[], globalColors: string[]) => {