Real Page Flip Engine for Flutter

A professional, high-fidelity 3D-like page flip engine for Flutter. Specifically engineered to deliver ultra-smooth 60/120 FPS performance even on low-end devices through advanced rendering optimizations.

English | 한국어

Demos

1. Full Performance Demo (v1.2+)

2. Legacy Interaction Demo (Core Physics)

Why Real Page Flip? (The Technical Edge)

Most page flip libraries struggle with performance as UI complexity increases. Real Page Flip is built differently:

1. Hybrid Snapshot Engine (GPU Optimization)

Unlike other libraries that attempt to render live widget trees during heavy animations, our engine captures high-resolution snapshots of your pages.

• The Benefit: During a flip, the GPU only handles a single flattened texture (RawImage) instead of hundreds of nested widgets. This guarantees silky-smooth motion even with extremely complex page layouts.

2. Intelligent Memory Windowing

Whether your book has 10 pages or 10,000, the memory footprint remains constant.

• The Benefit: We only maintain the current, previous, and next pages in the widget tree. This prevents the "Memory Bloat" common in standard PageView-based implementations.

3. Zero-Overhead Geometry Engine

We avoid heavy 3D perspective transforms that can be jittery on older hardware. Instead, we use a custom math-based Path Clipping engine.

• The Benefit: Perfectly clean curls, dynamic shadows, and specular highlights with minimal computational overhead.

4. Production-Hardened Layouts (Single Constraint Gate)

Ever had a "Vertical viewport was given unbounded height" error? Not here.

• The Benefit: Our internal "Constraint Gate" ensures the engine works perfectly inside any parent—be it a Stack, Column, or Scaffold—without manual size adjustments.

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Sensory Experience: Sound and Haptics

What truly sets this engine apart is the immersive sensory feedback:

• Physical Sound Effects: High-quality rustle sounds that vary naturally with your gesture speed.
• Tactile Haptics: Feel the friction and the "snap" of the paper through your device's haptic engine.

Installation

Add real_page_flip to your pubspec.yaml:

dependencies:
  real_page_flip: ^1.4.0

Quick Start

import 'package:real_page_flip/real_page_flip.dart';

PageFlipWidget(
  itemCount: 10,
  itemBuilder: (context, index) => MyPage(index),
)

Flip Sensitivity

Control the drag-release threshold for completing page flips in each direction:

PageFlipWidget(
  config: PageFlipConfig(
    // Forward flip completes when drag exceeds 40 % (default 0.4)
    cutoffForward: 0.35,
    // Backward flip threshold (default 0.4)
    cutoffPrevious: 0.5,
    // Overall gesture sensitivity (0.0 = firm, 1.0 = light touch)
    sensitivity: 0.5,
  ),
  itemCount: 10,
  itemBuilder: (context, index) => MyPage(index),
)

Higher values require dragging further across the page to complete a flip. Setting forward/previous independently lets you tune bias (e.g. easier to go forward than backward).

Double-spread (two-page) mode

For books that show left and right pages together:

PageFlipWidget(
  spreadMode: PageFlipSpreadMode.doubleSpread, // or isDoubleSpread: true
  itemCount: spreadCount, // number of spreads, not single pages
  config: PageFlipConfig(
    skipTapAnimation: false, // required to animate spine-band reveal on tap
  ),
  itemBuilder: (context, spreadIndex) => MyTwoPageSpread(spreadIndex),
)

Host contract

Responsibility	Detail
itemBuilder	Each index renders a full-width spread (left + right pages).
itemCount	Number of spreads (e.g. ceil(pageCount / 2)).
Stable builder	Use a method or const closure—not a new inline lambda every build, or snapshots reset too often.
Snapshots	The engine captures spreadSnapshots[currentIndex ± 1] when includeCurrentSpread is true (flip start, page settle, init).
Spine reveal	Forward flip reveals the left half of the next spread; backward reveals the right half of the previous spread.

Use clipSpreadPageHalf from the engine when aligning host layout with flip layers.

Dark Mode Support

The engine is theme-aware by default. With backgroundColor: null (the default since v1.3.0), the flipping page automatically uses the host app's scaffoldBackgroundColor, and shadow/highlight intensities are calculated from the background luminance at paint time.

Zero-config automatic dark mode

MaterialApp(
  theme: ThemeData.light(),
  darkTheme: ThemeData.dark(),
  themeMode: ThemeMode.system,
  home: Scaffold(
    body: PageFlipWidget(
      itemCount: pages.length,
      itemBuilder: (context, index) => MyPage(index),
      // No config needed — dark mode just works
    ),
  ),
)

Custom dark paper color

final isDark = Theme.of(context).brightness == Brightness.dark;

PageFlipWidget(
  config: PageFlipConfig(
    backgroundColor: isDark
        ? const Color(0xFF1A1F3A)  // dark navy
        : const Color(0xFFEEEEEE), // warm paper
  ),
  itemCount: pages.length,
  itemBuilder: (context, index) => MyPage(index),
)

What adapts automatically

Element	Light mode	Dark mode
Paper back color	scaffoldBackgroundColor	scaffoldBackgroundColor
Inner shadow strength	35 %	20 % (softer)
Fold highlight	5 %	18 % (stronger for depth)
Edge tap indicator	Dark glow	Light glow

Note: Page content (text, images, backgrounds) is controlled by your itemBuilder. The engine only manages the flip animation layer.

License

This project uses a Dual License model:

• Non-commercial: Free for personal/open-source projects.
• Commercial: Requires a paid license for revenue-generating products. See LICENSE for details.

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한국어 (Korean)

Real Page Flip Engine은 플러터를 위한 고성능 물리 기반 페이지 전환 엔진입니다. 특히 저사양 기기에서도 끊김 없는 60/120 FPS 성능을 보장하기 위해 설계된 독보적인 렌더링 최적화 기술이 적용되었습니다.

기술적 차별점 (Professional Edge)

1. 하이브리드 스냅샷 엔진: 애니메이션 중 복잡한 위젯 트리를 매 프레임 다시 그리는 대신, 페이지를 고해상도 이미지로 캡처하여 처리합니다. 덕분에 아무리 복잡한 UI라도 GPU 부하 없이 부드럽게 넘어갑니다.
2. 지능형 메모리 윈도잉: 수만 장의 페이지가 있어도 현재와 앞뒤 페이지, 단 3장만 메모리에 유지하여 리소스 낭비를 원천 차단합니다.
3. 제로-오버헤드 지오메트리: 무거운 3D 변환 대신 정교한 수학적 경로 클리핑(Path Clipping)을 사용하여 깨끗한 종이 휘어짐과 그림자 효과를 구현했습니다.
4. 견고한 레이아웃 설계: 'Constraint Gate' 구조를 통해 어떤 복잡한 위젯 트리 안에서도 레이아웃 에러 없이 안정적으로 작동합니다.

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