morphnext

Morph into what’s next.

morphnext turns bundled Flutter IconData glyphs into interruptible, spring-driven vector morphs without requiring per-pair animation assets.

Install

flutter pub add morphnext

Requires Dart >=3.9.0 and Flutter >=3.32.0.

Implicit morph

Change icon; AnimatedMorphIcon starts from the shape currently on screen, even when a new target interrupts an active transition.

import 'package:flutter/material.dart';
import 'package:morphnext/morphnext.dart';

IconButton(
  onPressed: () => setState(() => open = !open),
  icon: AnimatedMorphIcon(
    icon: open ? Icons.close : Icons.menu,
    semanticLabel: open ? 'Close menu' : 'Open menu',
  ),
)

Use onEnd when the next action must wait for the spring to finish and the target to settle on its final vector frame.

AnimatedMorphIcon uses MorphSprings.snappy by default. Select MorphSprings.smooth for a critically damped transition, or pass Flutter's SpringDescription directly for custom physics.

The widgets accept the same visual font controls as Flutter's Icon: fill, weight, grade, opticalSize, shadows, blendMode, and fontWeight. Values not supplied directly are inherited from IconTheme.

Controlled morph

Use any Animation<double> for gestures, scrolling, or a timeline. Progress is clamped to 0–1.

MorphIcon(
  from: Icons.favorite_border,
  to: Icons.favorite,
  progress: controller,
  size: 32,
  color: Colors.red,
  semanticLabel: 'Favorite',
)

Font compatibility

There is no fontAsset argument. IconData identifies a code point, font family, package, and fallback families—not an asset path. morphnext uses those fields and Flutter's font manifest to resolve fonts bundled through pubspec.yaml.

If a font is loaded only at runtime, missing, malformed, or unsupported, morphnext preserves the widget layout and displays regular Flutter icons instead. The UI remains usable, but that transition is not a continuous vector morph.

Flutter conventions

size, color, opacity, variable axes, shadows, optional text scaling, and directionality follow IconTheme, MediaQuery, and Directionality like Flutter's Icon. matchTextDirection is honored in RTL layouts. Set semanticLabel for one semantic image node; leave it null for a decorative icon. When MediaQuery.disableAnimations is true, AnimatedMorphIcon settles immediately.

Performance and caching

Fonts and morph plans are loaded lazily and cached with bounded memory use. Animation repaints directly without rebuilding the widget on every frame.

The application-wide morph cache has limits similar to Flutter's image cache. It is shared by morphnext widgets in the current Dart isolate. The defaults work without configuration. Applications that need explicit limits can set both before runApp:

MorphCache.configure(
  maxMorphs: 100,
  maxBytes: 16 * 1024 * 1024,
);

maxMorphs counts completed morphs retained for reuse. A → B and B → A, LTR and RTL, and different font parameters are separate morphs. One-off morphs from an interrupted intermediate shape are not retained. A morph larger than maxBytes is still built and used by the current animation, but it is not cached and does not evict existing entries.

currentMorphs and currentBytes expose the current cache statistics. Pending morphs are not counted. currentBytes is the size of vector buffers owned by retained morphs; it excludes decoded fonts, sampled source shapes, Dart object overhead, and memory owned by Flutter. Use MorphCache.clear() to empty the cache, MorphCache.disable() to empty and disable it, and MorphCache.reset() to restore defaultMaxMorphs and defaultMaxBytes. configure throws ArgumentError unless both limits are positive.

Limitations

morphnext preserves filled contour topology and keeps holes open, but arbitrary icon pairs can still produce an artistically surprising intermediate shape. The renderer is monochrome and accepts bundled font-backed IconData; it does not morph arbitrary Flutter Path objects or SVG artwork.

Examples

example/example.dart is the compact pub.dev example. The app in example/lib/main.dart powers the GitHub Pages showcase and interactive playground.

License and attribution

morphnext is MIT licensed. Parts of its geometry behavior are adapted from MIT-licensed Morphicons, and its font reader is derived from the MIT-licensed icon_font_generator; exact revisions and notices are in THIRD_PARTY_NOTICES.md.

This is an independent project. It is not affiliated with or endorsed by the Flutter project or the Morphicons project.