curved_roadmap

Curved, winding roadmap and journey paths for Flutter — the road-shaped progress graphic used in onboarding flows, learning paths, project timelines and slide-deck infographics.

Pure Dart and Flutter: no platform channels, no native dependencies, and it runs on all six platforms.

Markers + progress	Marker cards	Gradient + animation

Serpentine milestones	Serpentine with map pins	Captions beside the road

Every screen above is in the example app, along with horizontal scrollable roads, curve variants, theming and arbitrary placement.

Install

dependencies:
  curved_roadmap: ^0.1.0

Quick start

import 'package:curved_roadmap/curved_roadmap.dart';

CurvedRoadmap(
  geometry: const RoadmapGeometry(curveCount: 3),
  style: const CurvedRoadmapStyle(roadColor: Colors.black87),
  progress: 0.4,
  markers: [
    for (int i = 1; i <= 5; i++)
      RoadmapMarker(
        distanceFraction: i / 6,
        semanticLabel: 'Level $i',
        onTap: () => print('Level $i'),
        child: CircleAvatar(child: Text('$i')),
      ),
  ],
)

The road fills its parent's constraints, so give it a bounded box — a Scaffold body, an Expanded, or a SizedBox.

What you can control

Want to…	Use
Change the road's shape	`curveStyle` — S-curve, serpentine, zigzag, sine, straight
Draw a printed-style infographic	`SerpentineCurveStyle`
Place captions beside the road	`RoadmapMarker.side`
Position the road in its box	`alongStart`/`alongEnd`
Shape every turn by hand	`WaypointCurveStyle`
Show completion	`progress`
Animate it in	`animate`
Go longer than one screen	`RoadmapSizing.fixedSegmentExtent`

Placing the road: anywhere, any length

The road always spans exactly the extent you ask for — curveCount changes how tight the turns are, never how much space the road takes. Use alongStart/alongEnd (fractions of the winding axis) to place it:

// Only the top half of the box.
CurvedRoadmap(
  geometry: const RoadmapGeometry(alongStart: 0.5, alongEnd: 0.0),
)

Field	What it controls
`geometry.alongStart` / `alongEnd`	Where the road begins and ends — any position, any length. Swap them to run it backwards
`sizing.crossExtent`	Fixes the road's width in pixels (required under unbounded constraints)
`RoadmapSizing.fixedSegmentExtent`	Fixed pixels per segment, for roads longer than one screen
`geometry.orientation`	Which axis it winds along

It composes normally — drop it in a Card, a Row, a ListView item, or anywhere else; it sizes to its constraints like any other widget.

Configuration is split by concern

Object	Owns	Themable
`CurvedRoadmapStyle`	Paint: colors, stroke width, gradient, centerline	Yes, via `ThemeExtension`
`RoadmapGeometry`	Shape: curve style, turn count, amplitude, orientation, extent	No
`RoadmapSizing`	Layout: fit-to-parent or fixed pixels per segment	No
`progress` (widget)	State: how far along the road is	No

CurvedRoadmap(
  style: const CurvedRoadmapStyle(
    roadColor: Colors.brown,
    roadWidth: 24,
    lineColor: Colors.amber,
    lineStyle: RoadLineStyle.dashed, // or .solid / .none
  ),
  geometry: const RoadmapGeometry(
    curveCount: 4,
    curveAmplitude: 0.45, // 0.0-0.5, fraction from center
    orientation: RoadmapOrientation.vertical, // or .horizontal
  ),
  progress: 0.4,
)

Only paint lives in the theme extension, so theming colors never drags layout or progress state along with it.

Or set it once for a whole subtree via ThemeData.extensions:

Theme(
  data: Theme.of(context).copyWith(
    extensions: [const CurvedRoadmapStyle(roadColor: Colors.brown)],
  ),
  child: const CurvedRoadmap(), // picks up the style automatically
)

Milestones / markers

Place widgets along the path — icons, avatars, labels — with tap callbacks:

CurvedRoadmap(
  markers: [
    RoadmapMarker(
      distanceFraction: 0.25, // 0.0 (start) - 1.0 (end)
      onTap: () => print('Level 1'),
      child: const CircleAvatar(child: Icon(Icons.star)),
    ),
  ],
)

Progress fill

CurvedRoadmap(
  progress: 0.4, // 0.0-1.0
  style: const CurvedRoadmapStyle(completedColor: Colors.orange),
)

completedColor falls back to the ambient ColorScheme.primary.

Draw-in animation

CurvedRoadmap(
  animate: true,
  animationDuration: const Duration(seconds: 2),
)

Gradient stroke

CurvedRoadmap(
  style: const CurvedRoadmapStyle(
    roadGradient: LinearGradient(colors: [Colors.purple, Colors.orange]),
  ),
)

Curve style variants

curveStyle swaps the road's shape entirely — SCurveStyle (default), SerpentineCurveStyle, ZigzagCurveStyle, SineCurveStyle, or StraightCurveStyle:

CurvedRoadmap(
  geometry: const RoadmapGeometry(curveStyle: SineCurveStyle()),
)

Infographic roadmaps

SerpentineCurveStyle is the classic printed-roadmap layout: straight runs joined by U-turns at alternating ends, one row of milestones per run.

CurvedRoadmap(
  geometry: const RoadmapGeometry(
    curveStyle: SerpentineCurveStyle(rows: 3),
    curveAmplitude: 0.44,
  ),
  style: const CurvedRoadmapStyle(
    roadColor: Color(0xFF2E2E2E),
    roadWidth: 26,
    borderColor: Color(0xFFBDBDBD), // kerb/casing under the tarmac
    borderWidth: 3,
  ),
  markers: [
    RoadmapMarker.milestone(
      distanceFraction: 0,
      label: 'START',
      diameter: 104,
    ),
    RoadmapMarker.milestone(
      distanceFraction: 0.25,
      label: '1',
      title: 'DISCOVERY',
      body: 'Lorem ipsum dolor sit amet, consectetuer adipiscing elit.',
      color: Colors.teal,
    ),
  ],
)

Nodes on, over or under the road

side decides where a marker's content sits relative to the road, and sideOffset how far clear of the tarmac it sits:

CurvedRoadmap(
  markers: [
    // The pin sits on the path...
    RoadmapMarker.pin(distanceFraction: 0.25, label: '01'),
    // ...and its caption sits clear of it, swapping sides down the road.
    RoadmapMarker(
      distanceFraction: 0.25,
      side: RoadSide.alternating, // or .left / .right / .on
      sideOffset: 24,             // gap from the road's edge, not its centre
      child: const MyCaption(),
    ),
  ],
)

`RoadSide`	Where the content goes
`on`	Straddling the path (the default)
`left` / `right`	Clear of the road, relative to its direction of travel
`alternating`	Swaps side by list position — even index left, odd right

Sides follow the road, not the screen: left stays on the same side of the tarmac whether that stretch runs up, down or across, because placement is computed from the road's tangent at that point. sideOffset is measured from the road's edge, so it stays a true clearance when roadWidth changes.

Side-placed markers are not clamped back inside the widget — pulling them in would drag them onto the road they were asked to sit clear of. Give the widget enough room, or set keepInBounds: true on the marker to override.

For finer control, anchor picks which point of the marker meets its placement point; it defaults to facing the content's inner edge at the road.

RoadmapMarker.milestone puts a ringed circle on the road with its caption hanging beneath; RoadmapMarker.pin drops a teardrop map pin whose tip rests on the path (it anchors on its tip rather than its centre — see RoadmapMarker.anchor if you need that for your own markers).

The turns are semicircles when there's room and flatten into ellipses when there isn't, so the runs never collapse on a narrow box. This layout wants width: give it a wide box, or scroll it horizontally, as the example does.

Full manual control over the curves

Presets (SCurveStyle, ZigzagCurveStyle, etc.) use uniform curveCount/ curveAmplitude. For complete control over every turn — how far it swings, where it sits, and whether it's a smooth curve or a sharp corner — use WaypointCurveStyle:

CurvedRoadmap(
  geometry: const RoadmapGeometry(
    curveStyle: WaypointCurveStyle([
      RoadWaypoint(cross: 0.15),
      RoadWaypoint(cross: 0.85),
      RoadWaypoint(cross: 0.3, turn: RoadTurnType.sharp),
      RoadWaypoint(cross: 0.9),
    ]),
  ),
)

cross (0.0-1.0) is how far that turn swings across the road; at (0.0-1.0 along the road) is optional and defaults to even spacing; turn picks smooth vs. sharp per turn. For total control beyond that, CustomCurveStyle hands you the canvas size and style and lets you build the Path yourself:

CurvedRoadmap(
  geometry: RoadmapGeometry(
    curveStyle: CustomCurveStyle((size, geometry) {
      // geometry.mapProgress(t, cross, size) honors orientation/extent.
      return Path()
        ..moveTo(0, size.height)
        ..lineTo(size.width, 0);
    }),
  ),
)

Hoist a CustomCurveStyle's function to a field or top-level function rather than writing it inline — curve styles are compared to decide when to repaint, and a fresh closure each build repaints every frame.

Rich marker content — images, titles, notes

RoadmapMarker.child accepts any widget, so anything (an Image, a Column of your own design, a custom-painted badge) can sit on the road. For the common case — an icon/image plus a title and notes — RoadmapMarker.card builds it for you:

CurvedRoadmap(
  markers: [
    RoadmapMarker.card(
      distanceFraction: 0.3,
      title: 'Rest stop',
      notes: 'Great photo spot',
      icon: Icons.landscape, // or `image: Image.asset(...)`
      color: Colors.teal,
      onTap: () => print('tapped'),
    ),
  ],
)

Pass semanticLabel on markers you build yourself — tappable markers are exposed to screen readers as buttons, and a button with no label is invisible to them. RoadmapMarker.card labels itself from its title and notes.

Markers are measured and kept inside the widget's bounds, so wide content near an edge shifts inward instead of overflowing. Turn that off per marker with keepInBounds: false (or globally via CurvedRoadmap.keepMarkersInBounds), and nudge a marker off the road with offset: const Offset(0, -40).

Scrollable, longer-than-one-screen roadmaps

Use RoadmapSizing.fixedSegmentExtent and wrap in a SingleChildScrollView along the winding axis. Length follows the shape's own segment count, so a WaypointCurveStyle grows with the turns you placed:

SingleChildScrollView(
  scrollDirection: Axis.horizontal,
  child: CurvedRoadmap(
    geometry: const RoadmapGeometry(
      orientation: RoadmapOrientation.horizontal,
      curveCount: 8,
    ),
    sizing: const RoadmapSizing.fixedSegmentExtent(260),
  ),
)

Accessibility

Tappable markers are exposed as buttons and merge their child's labels, so a Text or a labelled Icon announces itself. For markers whose content carries no text of its own, pass semanticLabel — an unlabelled button is invisible to screen reader users.

Contributing

Issues and pull requests are welcome at github.com/Joynul-Abedin/curved_Line.

flutter test                       # everything, including goldens
flutter test --exclude-tags golden # skip goldens off the reference platform
flutter test --update-goldens      # after an intended visual change

Golden images are rendered by a specific engine version and host platform, so they are tagged golden and expected to differ elsewhere.

License

MIT — see LICENSE.