Ignite UI for Angular — Theming Skill

Description

This skill teaches AI agents how to theme Ignite UI for Angular applications using the Sass-based theming system and the Ignite UI Theming MCP server. It covers global themes, palettes, typography, elevations, component-level theming, layout controls (spacing, sizing, roundness), and how to use the MCP tools for code generation.

Prerequisites

• An Angular project with igniteui-angular installed, or @infragistics/igniteui-angular for licensed users
• Sass support enabled in the project (default for Angular CLI projects)

Ignite UI Theming MCP Server (recommended, not required)

The igniteui-theming MCP server generates production-ready theme code (createtheme, createpalette, createcomponenttheme, getcomponentdesigntokens, getcolor, and more). When its tools are available, prefer them over writing theme Sass from memory — start by calling detect_platform.

If the tools are not available, do not block the task — use the manual Sass workflow in this file. Suggest that the user run npx -y igniteui-cli ai-config from the project root (it configures both the igniteui-cli and igniteui-theming MCP servers) and reload the editor. MCP servers cannot be started mid-session; the configuration takes effect on the next session. Editor-specific details are in [references/mcp-setup.md](./references/mcp-setup.md).

Theming Architecture

Docs: Theming Overview · Palette · Typography · Elevations

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 include a pre-built CSS file in angular.json:

"styles": ["node_modules/igniteui-angular/styles/igniteui-angular.css"]

Licensed package users: replace igniteui-angular with @infragistics/igniteui-angular in the path:
```json
"styles": ["node_modules/@infragistics/igniteui-angular/styles/igniteui-angular.css"]
```

Available pre-built CSS files:

All files are located under nodemodules/igniteui-angular/styles/ (or nodemodules/@infragistics/igniteui-angular/styles/ for the licensed package).

Custom Sass Theme (Manual)

Important — Sass Theming Docs: If the user explicitly asks to build a Sass-based theme or configure Sass, refer to the dedicated Sass documentation:

- Sass Theming Overview
- Sass Configuration
- Sass Palettes
- Sass Component Themes

Create a styles.scss file and include it in angular.json:

// Open-source package
@use 'igniteui-angular/theming' as *;
// Licensed package — same Sass API, different import path
// @use '@infragistics/igniteui-angular/theming' as *;
$my-palette: palette(
  $primary: #1976d2,
  $secondary: #ff9800,
  $surface: #fafafa,
);

// 2. Typography (optional)
@include typography($font-family: $material-typeface, $type-scale: $material-type-scale);

// 3. Core reset & base styles
@include core();

// 4. Apply theme
@include theme($palette: $my-palette, $schema: $light-material-schema);

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

$dark-palette: palette(
  $primary: #90caf9,
  $secondary: #ffb74d,
  $surface: #121212,
);

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

Component-Level Theming

Docs: Component Themes

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

All color values passed to component themes must be palette tokens, not raw hex/RGB/HSL — see [No Hardcoded Colors After Palette Generation](#no-hardcoded-colors-after-palette-generation) below.

@use 'igniteui-angular/theming' as *;

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

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

Layout Controls

Sizing

Docs: Display Density / Sizing

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

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

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

Spacing

Docs: 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;
}
igx-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.

File safety: When applying generated theme code to an existing style file, make targeted edits that preserve the user's existing custom styles — never wholesale-replace the file contents. If the environment does not gate file writes behind user approval, present the change as a diff for review before writing.

Always follow this workflow:

Step 1 — Detect Platform

Tool: detect_platform

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

Step 2 — Generate a Full Theme

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

Step 4 — Generate a Palette

For simple mid-luminance base colors:

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

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

Step 5 — Adjust Layout

Tool: set_size     → { size: "medium" }
Tool: set_spacing  → { spacing: 0.75, component: "grid" }
Tool: set_roundness → { radiusFactor: 0.8 }

Step 6 — Reference Palette Colors via get_color

After a palette is generated, use the get_color tool to obtain the correct CSS custom property reference for any color you need (see [No Hardcoded Colors After Palette Generation](#no-hardcoded-colors-after-palette-generation)):

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)

Loading Reference Data

Use read_resource with these URIs for preset values and documentation:

No Hardcoded Colors After Palette Generation

This is the single most important theming rule. Once a palette exists (via palette() in Sass or createpalette / createtheme via MCP), every color reference must come from the palette tokens, which are available as CSS custom properties on :root. This applies to all style code: component theme tokens values, custom CSS rules (color, background, border-color, fill, stroke), Sass variables for derived values, Angular host bindings, and inline styles. Hardcoded values break theme switching and drift out of sync when the palette changes.

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
$primary-color: #00838f; // ✗ hardcoded
$secondary-color: #3d5afe; // ✗ hardcoded
$surface-color: #f0f5fa; // ✗ hardcoded

.sidebar {
  background: $surface-color; // ✗ 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. createpalette / createtheme 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

Light/dark theme switching, scoped themes, and licensed package configuration are in [references/common-patterns.md](./references/common-patterns.md). Read that file for ready-to-use Sass patterns.

Key Rules

1. Preserve existing styles — apply theme code as targeted edits to existing style files; never wholesale-replace a file the user has customized
2. Always call detect_platform first when using MCP tools
3. Always call getcomponentdesigntokens before createcomponent_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. Use @include core() once before @include theme() in your global styles
7. Component themes use @include tokens($theme) inside a selector to emit CSS custom properties
8. For compound components, follow the full checklist returned by getcomponentdesign_tokens — theme each child component with its scoped selector
9. No hardcoded colors after palette generation — see [No Hardcoded Colors After Palette Generation](#no-hardcoded-colors-after-palette-generation); raw hex/RGB/HSL is only acceptable in the initial palette seed values

Related Skills

• [igniteui-angular-components](../igniteui-angular-components/SKILL.md) — UI components (form controls, layout, data display, feedback/overlays, directives, charts)
• [igniteui-angular-grids](../igniteui-angular-grids/SKILL.md) — Data Grids (Flat Grid, Tree Grid, Hierarchical Grid, Grid Lite, Pivot Grid)