Igniteui Wc Customize Component Theme

Ignite UI Web Components — Theming Skill

Description

This skill teaches AI agents how to theme Ignite UI Web Components (and React via igniteui-react) applications. Two approaches are supported:

• CSS custom properties — works in any project without additional build tooling
• Sass — available when the project has Sass configured; provides the full palette/typography/elevation API

The skill also covers component-level theming, layout controls (spacing, sizing, roundness), and how to use the Ignite UI Theming MCP server for AI-assisted code generation.

Prerequisites

• A project with igniteui-webcomponents (or igniteui-react) installed
• The Ignite UI Theming MCP server (igniteui-theming) available as a tool provider
• Optional: Sass configured in the project (enables the Sass-based theming API)

AGENT INSTRUCTION — MCP Server Setup (REQUIRED)

Before using any theming tools, you MUST verify the MCP server is available by calling detect_platform. If the tool is not available or the call fails, you MUST automatically configure it by following the setup process steps described below.

After writing the file, inform the user that the MCP server has been configured and they may need to reload the editor for the tools to activate. Start the MCP server and wait for that MCP server to start before continuing the theming related work. Do NOT skip this step or ask the user to do it manually.

Setting Up the Theming MCP Server

The Ignite UI Theming MCP server enables AI assistants to generate production-ready theming code. It must be configured in your editor before the theming tools become available.

VS Code

Create or edit .vscode/mcp.json in your project:

{
  "servers": {
    "igniteui-theming": {
      "command": "npx",
      "args": ["-y", "igniteui-theming", "igniteui-theming-mcp"]
    }
  }
}

This works whether igniteui-theming is installed locally in node_modules or needs to be pulled from the npm registry — npx -y handles both cases.

Cursor

Create or edit .cursor/mcp.json:

{
  "mcpServers": {
    "igniteui-theming": {
      "command": "npx",
      "args": ["-y", "igniteui-theming", "igniteui-theming-mcp"]
    }
  }
}

Claude Desktop

Edit the Claude Desktop config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "igniteui-theming": {
      "command": "npx",
      "args": ["-y", "igniteui-theming", "igniteui-theming-mcp"]
    }
  }
}

WebStorm / JetBrains IDEs

1. Go to Settings → Tools → AI Assistant → MCP Servers
2. Click + Add MCP Server
3. Set Command to npx and Arguments to igniteui-theming igniteui-theming-mcp
4. Click OK and restart the AI Assistant

Verifying the Setup

After configuring the MCP server, ask your AI assistant:

"Detect which Ignite UI platform my project uses"

If the MCP server is running, the detect_platform tool will analyze your package.json and return the detected platform (e.g., webcomponents).

Theming Architecture

The Ignite UI theming system is built on four pillars:

Design Systems

Four built-in design systems are available:

• Material (default) — Material Design 3
• Bootstrap — Bootstrap-inspired
• Fluent — Microsoft Fluent Design
• Indigo — Infragistics Indigo Design

Each has light and dark variants (e.g., $light-material-schema, $dark-fluent-schema).

Pre-built Themes

The quickest way to theme an app is to import a pre-built CSS file in your entry point:

import 'igniteui-webcomponents/themes/light/bootstrap.css';

Available pre-built CSS files:

Custom Theme via CSS Custom Properties

No Sass required. Works in any project after importing a pre-built theme.

After importing a pre-built theme, override individual design tokens with CSS custom properties on :root or a scoped selector:

:root {
  /* Override palette hue/saturation/lightness channels */
  --ig-primary-h: 211deg;
  --ig-primary-s: 100%;
  --ig-primary-l: 50%;

  --ig-secondary-h: 33deg;
  --ig-secondary-s: 100%;
  --ig-secondary-l: 50%;
}

To scope overrides to a specific container:

.admin-panel {
  --ig-primary-h: 260deg;
  --ig-primary-s: 60%;
  --ig-primary-l: 45%;
}

For dark mode, either import a dark theme CSS file directly or toggle overrides with a class or media query:

@media (prefers-color-scheme: dark) {
  :root {
    --ig-surface-h: 0deg;
    --ig-surface-s: 0%;
    --ig-surface-l: 7%;
  }
}

/* Or manually with a class */
.dark-theme {
  --ig-surface-h: 0deg;
  --ig-surface-s: 0%;
  --ig-surface-l: 7%;
}

Custom Theme via Sass

Requires Sass configured in the project. First check whether the project has a Sass setup (e.g., a styles.scss entry file, sass in devDependencies, or a Vite/webpack Sass plugin).

The Sass API for igniteui-webcomponents uses @use 'igniteui-theming' with individual mixins — not the Angular-specific core() / theme() combined mixins.

@use 'igniteui-theming' as *;

// 1. Define a palette
$my-palette: palette(
  $primary: #1976D2,
  $secondary: #FF9800,
  $surface: #FAFAFA
);

// 2. Apply the palette
@include palette($my-palette);

// 3. Optional: Typography
@include typography($font-family: "'Roboto', sans-serif");

// 4. Optional: Elevations
@include elevations();

// 5. Optional: Spacing
@include spacing();

For dark themes, use a dark surface color and a dark schema:

@use 'igniteui-theming' as *;

$dark-palette: palette(
  $primary: #90CAF9,
  $secondary: #FFB74D,
  $surface: #121212
);

@include palette($dark-palette, $schema: $dark-material-schema);

To scope a Sass theme to a container:

.admin-panel {
  @include palette($admin-palette, $schema: $light-indigo-schema);
}

Component-Level Theming

Override individual component appearance using component theme functions and the tokens mixin.

AGENT INSTRUCTION — No Hardcoded Colors (CRITICAL)

Once a palette has been generated (via palette() in Sass or create_palette / create_theme via MCP), every color reference MUST come from the generated palette tokens — never hardcode hex/RGB/HSL values.

Use var(--ig-primary-500), var(--ig-secondary-300), var(--ig-surface-500), etc. in CSS, or the get_color MCP tool to obtain the correct token reference.

WRONG (hardcoded hex — breaks theme switching, ignores the palette):

igc-avatar {
  --ig-avatar-background: #E91E63;  /* ✗ hardcoded */
  --ig-avatar-color: #FFFFFF;       /* ✗ hardcoded */
}

RIGHT — CSS (palette token — stays in sync with the theme):

igc-avatar {
  --ig-avatar-background: var(--ig-primary-500);
  --ig-avatar-color: var(--ig-primary-500-contrast);
}

RIGHT — Sass (when Sass is configured):

$custom-avatar: avatar-theme(
  $schema: $light-material-schema,
  $background: var(--ig-primary-500),
  $color: var(--ig-primary-500-contrast)
);

This applies to all style code: component themes, custom CSS rules, and inline styles. The only place raw hex values belong is the initial palette() call that seeds the color system. Everything downstream must reference the palette.

igc-avatar {
  --ig-avatar-background: var(--ig-primary-500);
  --ig-avatar-color: var(--ig-primary-500-contrast);
}

When Sass is available, use the component theme function and tokens mixin:

@use 'igniteui-theming' as *;

$custom-avatar: avatar-theme(
  $schema: $light-material-schema,
  $background: var(--ig-primary-500),
  $color: var(--ig-primary-500-contrast)
);

igc-avatar {
  @include tokens($custom-avatar);
}

Discovering Available Tokens

Each component has its own set of design tokens (themeable CSS custom properties). Before theming a component, you must know which tokens exist. Use the MCP tool get_component_design_tokens to discover them.

Compound Components

Some components (e.g., combo, grid, date-picker, select) are compound — they contain internal child components, each requiring their own theme. For example, date-picker uses calendar, flat-button, and input-group internally.

Workflow for compound components:

1. Call get_component_design_tokens for the parent (e.g., date-picker)
2. The response lists related themes and scope selectors
3. Call create_component_theme for each child, using the parent's selector as the wrapper

Layout Controls

Sizing

Controls the size of components via --ig-size (values: 1 = small, 2 = medium, 3 = large):

/* Global */
:root { --ig-size: 2; }

/* Component-scoped */
igc-grid { --ig-size: 1; }

Spacing

Controls internal padding via --ig-spacing (1 = default, 0.5 = compact, 2 = spacious):

:root { --ig-spacing: 1; }
.compact-section { --ig-spacing: 0.75; }

Roundness

Controls border-radius via --ig-radius-factor (0 = square, 1 = maximum radius):

:root { --ig-radius-factor: 1; }
igc-avatar { --ig-radius-factor: 0.5; }

Using the Theming MCP Server

The Ignite UI Theming MCP server provides tools for AI-assisted theme code generation.

IMPORTANT — File Safety Rule: When generating or updating theme code, never overwrite existing style files directly. Instead, always propose the changes as an update and let the user review and approve before writing to disk. If a styles.scss (or any target file) already exists, show the generated code as a diff or suggestion rather than replacing the file contents. This prevents accidental loss of custom styles the user has already written.

Always follow this workflow:

Step 1 — Detect Platform

Tool: detect_platform

This auto-detects webcomponents from package.json and sets the correct import paths.

Step 2 — Generate a Full Theme

Tool: create_theme
Params: {
  platform: "webcomponents",
  designSystem: "material",
  primaryColor: "#1976D2",
  secondaryColor: "#FF9800",
  surfaceColor: "#FAFAFA",
  variant: "light",
  fontFamily: "'Roboto', sans-serif",
  includeTypography: true,
  includeElevations: true
}

Generates a complete Sass file with palette, typography, elevations, and the theme() mixin call.

Step 3 — Customize Individual Components

Tool: get_component_design_tokens
Params: { component: "grid" }

Then use palette token references (not hardcoded hex values) for every color:

Tool: create_component_theme
Params: {
  platform: "webcomponents",
  designSystem: "material",
  variant: "light",
  component: "grid",
  tokens: {
    "header-background": "var(--ig-primary-50)",
    "header-text-color": "var(--ig-primary-800)"
  }
}

Reminder: After a palette is generated, all token values passed to create_component_theme must reference palette CSS custom properties (e.g., var(--ig-primary-500), var(--ig-secondary-A200), var(--ig-gray-100)). Never pass raw hex values like "#E3F2FD".

Step 4 — Generate a Palette

For simple mid-luminance base colors:

Tool: create_palette
Params: {
  platform: "webcomponents",
  primary: "#1976D2",
  secondary: "#FF9800",
  surface: "#FAFAFA",
  variant: "light"
}

For brand-specific exact shade values, use create_custom_palette with mode: "explicit" for full control over each shade.

Step 5 — Adjust Layout

By default, layout tools emit CSS. If the project has Sass configured, add output: "sass" to get Sass output:

Tool: set_size      → { size: "medium" }                                   # CSS (default)
Tool: set_size      → { size: "medium", output: "sass" }                   # Sass
Tool: set_spacing   → { spacing: 0.75, component: "grid" }                 # CSS (default)
Tool: set_spacing   → { spacing: 0.75, component: "grid", output: "sass" } # Sass
Tool: set_roundness → { radiusFactor: 0.8 }                                # CSS (default)
Tool: set_roundness → { radiusFactor: 0.8, output: "sass" }                # Sass

Step 6 — Reference Palette Colors (MANDATORY for All Color Usage)

After a palette is generated, always use the get_color tool to obtain the correct CSS custom property reference. Never hardcode hex/RGB/HSL values in component themes, custom CSS, or Sass variables.

Tool: get_color
Params: { color: "primary", variant: "600" }
→ var(--ig-primary-600)

Params: { color: "primary", variant: "600", contrast: true }
→ var(--ig-primary-600-contrast)

Params: { color: "primary", opacity: 0.5 }
→ hsl(from var(--ig-primary-500) h s l / 0.5)

Use these token references everywhere:

• Component theme tokens values
• Custom CSS rules (color, background, border-color, fill, stroke, etc.)

The only place raw hex values are acceptable is in the initial palette() call or the create_palette / create_theme MCP tool inputs that seed the color system.

Loading Reference Data

Use read_resource with these URIs for preset values and documentation:

Referencing Colors in Custom Styles

After a theme is applied, the palette is available as CSS custom properties on :root. Use these tokens in all custom CSS — never introduce standalone hex/RGB variables for colors that the palette already provides.

Correct: Palette Tokens

/* All colors come from the theme — respects palette changes and dark/light switching */
.sidebar {
  background: var(--ig-surface-500);
  color: var(--ig-gray-900);
  border-right: 1px solid var(--ig-gray-200);
}

.accent-badge {
  background: var(--ig-secondary-500);
  color: var(--ig-secondary-500-contrast);
}

.hero-section {
  /* Semi-transparent primary overlay */
  background: hsl(from var(--ig-primary-500) h s l / 0.12);
}

Incorrect: Hardcoded Values

/* WRONG — these break when the palette changes and ignore dark/light mode */
.sidebar {
  background: #F0F5FA;  /* ✗ not a palette token */
  color: #333;          /* ✗ not a palette token */
}

When Raw Hex Values Are OK

Raw hex values are acceptable only in these contexts:

1. palette() call — the initial seed colors that generate the full palette
2. create_palette / create_theme MCP tool inputs — the base colors passed to the tool
3. Non-palette decorative values — e.g., a one-off SVG illustration color that intentionally stays fixed regardless of theme

Everything else must use var(--ig-<family>-<shade>) tokens.

Common Patterns

Switching Between Light and Dark Themes — CSS approach

Import the appropriate theme CSS and toggle with a class or media query:

// In your entry point — choose one variant as the default
import 'igniteui-webcomponents/themes/light/bootstrap.css';

/* Override surface tokens for dark mode */
.dark-theme {
  --ig-surface-h: 0deg;
  --ig-surface-s: 0%;
  --ig-surface-l: 7%;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ig-surface-h: 0deg;
    --ig-surface-s: 0%;
    --ig-surface-l: 7%;
  }
}

Or dynamically swap the stylesheet at runtime:

function setTheme(variant: 'light' | 'dark', design = 'bootstrap') {
  const link = document.getElementById('igc-theme') as HTMLLinkElement;
  link.href = `node_modules/igniteui-webcomponents/themes/${variant}/${design}.css`;
}

Switching Between Light and Dark Themes — Sass approach

When Sass is configured, define both palettes and apply them under separate selectors:

@use 'igniteui-theming' as *;

$light-palette: palette($primary: #1976D2, $secondary: #FF9800, $surface: #FAFAFA);
$dark-palette: palette($primary: #90CAF9, $secondary: #FFB74D, $surface: #121212);

@include typography($font-family: "'Roboto', sans-serif");
@include elevations();

// Light is default
@include palette($light-palette, $schema: $light-material-schema);

// Dark via class on <body> or <html>
.dark-theme {
  @include palette($dark-palette, $schema: $dark-material-schema);
}

Scoping a Theme to a Container — CSS approach

.admin-panel {
  --ig-primary-h: 260deg;
  --ig-primary-s: 60%;
  --ig-primary-l: 45%;
}

Scoping a Theme to a Container — Sass approach

.admin-panel {
  @include palette($admin-palette, $schema: $light-indigo-schema);
}

Key Rules

1. Never overwrite existing files directly — always propose theme code as an update for user review; do not replace existing style files without confirmation
2. Always call detect_platform first when using MCP tools
3. Always call get_component_design_tokens before create_component_theme to discover valid token names
4. Palette shades 50 = lightest, 900 = darkest for all chromatic colors — never invert for dark themes (only gray inverts)
5. Surface color must match the variant — light color for light, dark color for dark
6. Sass only: Use @include palette(), @include typography(), and @include elevations() individually — @use 'igniteui-theming' is the correct module for web components and React (not igniteui-angular/theming); the Angular-specific core() / theme() combined mixins do not apply here
7. Sass only: Component themes use @include tokens($theme) inside a selector to emit CSS custom properties
8. For compound components, follow the full checklist returned by get_component_design_tokens — theme each child component with its scoped selector
9. Never hardcode colors after palette generation — once a palette is created, every color in component themes, custom CSS, and Sass variables must use var(--ig-<family>-<shade>) palette tokens (e.g., var(--ig-primary-500), var(--ig-gray-200)). Raw hex/RGB/HSL values are only acceptable in the initial palette() seed call. This ensures themes remain consistent, switchable (light/dark), and maintainable