flutter-deck-theming

name	flutter-deck-theming
description	Style flutter_deck presentations using FlutterDeckThemeData with lightTheme/darkTheme/themeMode, FlutterDeckTextTheme typography slots (display, header, title, subtitle, bodyLarge/Medium/Small), per-slide theme overrides via the slide-level theme: parameter and copyWith on template slots (titleSlideTheme, splitSlideTheme, quoteSlideTheme, imageSlideTheme, bigFactSlideTheme, slideTheme), and component theming for headers, footers, bullet lists, code highlight, and speaker info. Use this skill when establishing brand identity, switching light/dark modes, restyling a single slide, overriding sub-component styles, choosing typography, or auditing 4.5:1 contrast — even when the user only says "change the colors" or "make this slide pop".
compatibility	Requires a Flutter project with the flutter_deck package added as a dependency.

Styling and Theming Flutter Deck

Overview

The flutter_deck framework takes visual presentation seriously by providing its own theming engine, separate from (yet composable with) Flutter's standard ThemeData. FlutterDeckThemeData explicitly models the visual characteristics unique to presentations—like slide backgrounds, highly readable typography levels (title, subtitle, body), header/footer colors, and speaker notes styles. The system natively supports light and dark modes, allowing the presentation's brightness to follow system settings or user preference seamlessly. Moreover, themes can be localized to a single slide, or even specific widgets like the slide header or footer.

When to Use This Skill

• When establishing the company or brand's visual identity for the entire presentation.
• When you want to ensure the presentation seamlessly supports both light and dark display modes.
• When an individual slide requires a dramatic visual change (e.g., changing text and background color) using a localized FlutterDeckTheme.
• When trying to override the default styles of sub-components like the FlutterDeckHeader, FlutterDeckFooter, or FlutterDeckCodeHighlight.
• When using common Material widgets (like Buttons or Cards) inside slides to ensure they inherit aesthetic choices via FlutterDeckThemeData.fromTheme.

Implementation Checklist

• Determine the primary color scheme and fonts needed for the design.
• Supply FlutterDeckThemeData.fromTheme to the lightTheme and darkTheme parameters in FlutterDeckApp configured using your ThemeData.
• To isolate the theme of a single slide, wrap that slide's highest-level widget tree in FlutterDeckTheme and provide the overridden FlutterDeckTheme.of(context).copyWith(...).
• To customize built-in widget styles, wrap them in their respective theme widgets (e.g., FlutterDeckHeaderTheme).
• Verify that all text-to-background color pairings meet the 4.5:1 contrast ratio.

Accessibility Fundamentals

When designing presentation themes, you must adhere rigidly to Material accessibility standards so every viewer can read your slides comfortably, regardless of screen brightness or room lighting:

• Contrast Ratios: Every piece of text must maintain a minimum contrast ratio of 4.5:1 against its background color. Never place white text on very light backgrounds (like pastel cyan, yellow, or standard Colors.green).
• Dynamic Text Scaling: Ensure that when users (or the framework) scale up text sizes for visibility, your layouts adapt without overflowing or clipping.
• Color Semantics: Rely on ThemeData.colorScheme's semantic colors (e.g., onPrimary for text placed on top of primary color) rather than hardcoding absolute colors. The Flutter framework automatically calculates accessible "on" colors for the baseline palettes.

---

Global Deck Theme

You should customize the theme of your slide deck by providing a FlutterDeckThemeData to the FlutterDeckApp widget. The best practice is to extract your presentation aesthetics directly from a standard ThemeData block.

return FlutterDeckApp(
  // You can define light...
  lightTheme: FlutterDeckThemeData.fromTheme(
    ThemeData.from(
      colorScheme: ColorScheme.fromSeed(
        seedColor: const Color(0xFF005C97), // Strong, accessible seed color
      ),
      useMaterial3: true,
    ),
  ),
  // ...and dark themes.
  darkTheme: FlutterDeckThemeData.fromTheme(
    ThemeData.from(
      colorScheme: ColorScheme.fromSeed(
        seedColor: const Color(0xFF00E5FF),
        brightness: Brightness.dark,
      ),
      useMaterial3: true,
    ),
  ),
  slides: const [...],
);

Overriding Theme per Slide

It's possible to override the theme for a specific slide. The provided theme data will be merged with the global theme.

class ThemingSlide extends FlutterDeckSlideWidget {
  const ThemingSlide()
      : super(
          configuration: const FlutterDeckSlideConfiguration(
            route: '/theming-slide',
            header: FlutterDeckHeaderConfiguration(title: 'Theming'),
          ),
        );

  @override
  Widget build(BuildContext context) {
    return FlutterDeckSlide.split(
      theme: FlutterDeckTheme.of(context).copyWith(
        splitSlideTheme: const FlutterDeckSplitSlideThemeData(
          // Ensure high contrast: White text on deep blue (> 4.5:1)
          leftBackgroundColor: Color(0xFF0D47A1), // Colors.blue.shade900
          leftColor: Colors.white,
          // Ensure high contrast: Very dark grey text on soft amber (> 4.5:1)
          rightBackgroundColor: Color(0xFFFFECB3), // Colors.amber.shade100
          rightColor: Color(0xFF212121), // Colors.grey.shade900
        ),
      ),
      leftBuilder: (context) => const Text('Left'),
      rightBuilder: (context) => const Text('Right'),
    );
  }
}

Theme Surface

flutter_deck has two layers of theme widgets:

Widget-level themes — style a single reusable component:

• FlutterDeckBulletListTheme / FlutterDeckBulletListThemeData
• FlutterDeckCodeHighlightTheme / FlutterDeckCodeHighlightThemeData
• FlutterDeckFooterTheme / FlutterDeckFooterThemeData
• FlutterDeckHeaderTheme / FlutterDeckHeaderThemeData
• FlutterDeckSpeakerInfoWidgetTheme / FlutterDeckSpeakerInfoWidgetThemeData

Template-level themes — style the layout of a FlutterDeckSlide.<factory>:

• FlutterDeckBigFactSlideTheme / FlutterDeckBigFactSlideThemeData — bigFactSlideTheme
• FlutterDeckImageSlideTheme / FlutterDeckImageSlideThemeData — imageSlideTheme
• FlutterDeckQuoteSlideTheme / FlutterDeckQuoteSlideThemeData — quoteSlideTheme
• FlutterDeckSlideTheme / FlutterDeckSlideThemeData — slideTheme (used by blank, template, custom)
• FlutterDeckSplitSlideTheme / FlutterDeckSplitSlideThemeData — splitSlideTheme
• FlutterDeckTitleSlideTheme / FlutterDeckTitleSlideThemeData — titleSlideTheme

Each *ThemeData field is also reachable on FlutterDeckThemeData via the slot name shown above (e.g. FlutterDeckTheme.of(context).copyWith(splitSlideTheme: ...)), which is the per-slide override path used in the example below.

Per-template per-slide override

The slide-level theme: parameter (available on every FlutterDeckSlide.<factory>) plus copyWith is the most common way to restyle a single slide:

FlutterDeckSlide.split(
  theme: FlutterDeckTheme.of(context).copyWith(
    splitSlideTheme: const FlutterDeckSplitSlideThemeData(
      leftBackgroundColor: Color(0xFF0D47A1),
      leftColor: Colors.white,
      rightBackgroundColor: Color(0xFFFFECB3),
      rightColor: Color(0xFF212121),
    ),
  ),
  leftBuilder: (context) => const Text('Left'),
  rightBuilder: (context) => const Text('Right'),
);

Any of the eight template slots (bigFactSlideTheme, imageSlideTheme, quoteSlideTheme, slideTheme, splitSlideTheme, titleSlideTheme, plus the widget-level slots like headerTheme, footerTheme, codeHighlightTheme, bulletListTheme, speakerInfoWidgetTheme) can be passed to copyWith.

Wrapping individual built-in widgets

Alternatively, scope a theme to a single component subtree by wrapping it with the matching *Theme widget:

FlutterDeckSlide.template(
  // Wrap header with a theme widget to override the theme.
  headerBuilder: (context) => FlutterDeckHeaderTheme(
    data: FlutterDeckHeaderThemeData(
      color: const Color(0xFFB71C1C), // Deep red for adequate contrast
      textStyle: FlutterDeckTheme.of(context).textTheme.header.copyWith(
        color: Colors.white, // Explicitly safe white text
      ),
    ),
    child: const FlutterDeckHeader(title: 'Header'),
  ),
  // Wrap footer with a theme widget to override the theme.
  footerBuilder: (context) => FlutterDeckFooterTheme(
    data: FlutterDeckFooterThemeData(
      socialHandleColor: Colors.blue,
      socialHandleTextStyle:
          FlutterDeckTheme.of(context).textTheme.bodyMedium,
    ),
    child: const FlutterDeckFooter(showSlideNumber: false),
  ),
  contentBuilder: (context) => Center(
    // Wrap code highlight with a theme widget to override the theme.
    child: FlutterDeckCodeHighlightTheme(
      data: FlutterDeckCodeHighlightThemeData(
        backgroundColor: const Color(0xFF1B5E20), // Dark green background
        textStyle: FlutterDeckTheme.of(context).textTheme.bodyLarge.copyWith(
          color: Colors.white, // High contrast white text
        ),
      ),
      child: const FlutterDeckCodeHighlight(code: '<...>'),
    ),
  ),
);

Light / Dark Mode

FlutterDeckApp exposes three theme parameters:

• lightTheme — used in light mode.
• darkTheme — used in dark mode.
• themeMode — defaults to ThemeMode.system (follows the OS). Set to ThemeMode.light or ThemeMode.dark to lock.

Both themes are independent — flutter_deck does not derive one from the other. Provide both, or accept that the unset side falls back to its framework default (FlutterDeckThemeData.light / .dark).

Typography Slots (FlutterDeckTextTheme)

FlutterDeckThemeData.textTheme exposes seven typography slots, all TextStyle:

Slot	Default size	Used by
display	103 / bold	Big fact slide title
header	57	FlutterDeckHeader, slide headers
title	54	Title slide title
subtitle	42	Title slide subtitle
bodyLarge	28	Quote, default body
bodyMedium	22	Footer, secondary body
bodySmall	16	Footnotes, captions

Override individual slots with copyWith, or apply a font family deck-wide with FlutterDeckTextTheme.apply(fontFamily: ..., color: ...).

lightTheme: FlutterDeckThemeData.fromTheme(
  ThemeData.from(
    colorScheme: ColorScheme.fromSeed(seedColor: const Color(0xFFFF3366)),
    useMaterial3: true,
  ).copyWith(textTheme: GoogleFonts.outfitTextTheme()),
),

Gotchas

• FlutterDeckThemeData is not a drop-in for Flutter's ThemeData. Bridge them with FlutterDeckThemeData.fromTheme(ThemeData(...)) so Material widgets used inside slides inherit the deck palette.
• Per-slide overrides are merged with the global theme via FlutterDeckTheme.of(context).copyWith(...), not a full replacement. Only the fields you pass to copyWith change; everything else still comes from the global theme.
• Component theme widgets only affect their own widget. Wrapping the wrong subtree is silent — the override just doesn't apply. The full set is enumerated in the "Theme Surface" section above (5 widget-level + 6 template-level themes).
• For a single-slide restyle, prefer the slide-level theme: parameter + copyWith on a template slot (splitSlideTheme, titleSlideTheme, etc.) over wrapping individual builders. It's terser and applies to the whole slide.
• lightTheme and darkTheme are independent. flutter_deck does not derive one from the other — provide both, or accept that the unset side falls back to defaults. themeMode defaults to ThemeMode.system.
• Prefer semantic colors (colorScheme.onPrimary, onSurface, …) over hardcoded hex. The seed-based palette guarantees 4.5:1 contrast for on* pairings; hex values are easy to break when the seed color changes.