mc_gallery/lib/features/core/widgets/gap.dart

import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';

/// Const evenly-sized gap.
class Gap extends LeafRenderObjectWidget {
  const Gap(
    this.size, {
    super.key,
  });

  final double size;

  @override
  RenderGap createRenderObject(BuildContext context) => RenderGap(size);

  @override
  void updateRenderObject(BuildContext context, covariant RenderGap renderObject) {
    renderObject.gap = size;
    super.updateRenderObject(context, renderObject);
  }

  static const size4 = Gap(4);
  static const size8 = Gap(8);
  static const size16 = Gap(16);
  static const size24 = Gap(24);
  static const size32 = Gap(32);
  static const size64 = Gap(64);
}

class RenderGap extends RenderBox {
  RenderGap(this._gap) : super() {
    markNeedsLayout();
  }

  double _gap;
  double get gap => _gap;

  set gap(double value) {
    if (_gap != value) {
      _gap = value;
      markNeedsLayout();
    }
  }

  @override
  void performLayout() {
    final parent = this.parent;
    Size newSize;
    if (parent is RenderFlex) {
      switch (parent.direction) {
        case Axis.vertical:
          newSize = Size(0, gap);
          break;
        case Axis.horizontal:
          newSize = Size(gap, 0);
          break;
      }
    } else {
      newSize = Size.square(gap);
    }
    size = constraints.constrain(newSize);
  }
}

/// Animates [Gap] insertion.
class AnimatedGap extends StatefulWidget {
  const AnimatedGap(
    this.gap, {
    this.duration = const Duration(milliseconds: 200),
    this.curve = Curves.easeInOut,
    super.key,
  });

  final Duration duration;
  final double gap;
  final Curve curve;

  @override
  State<AnimatedGap> createState() => _AnimatedGapState();
}

class _AnimatedGapState extends State<AnimatedGap> with SingleTickerProviderStateMixin {
  late final _controller = AnimationController(
    vsync: this,
    value: widget.gap,
    upperBound: double.infinity,
  );

  @override
  void didUpdateWidget(covariant AnimatedGap oldWidget) {
    if (oldWidget.gap != widget.gap) {
      _controller.animateTo(
        widget.gap,
        curve: widget.curve,
        duration: widget.duration,
      );
    }
    super.didUpdateWidget(oldWidget);
  }

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<double>(
      valueListenable: _controller,
      builder: (context, gap, _) {
        return Gap(gap);
      },
    );
  }
}

class AnimatedSliverGap extends StatefulWidget {
  const AnimatedSliverGap(
    this.gap, {
    this.duration = const Duration(milliseconds: 200),
    this.curve = Curves.easeInOut,
    super.key,
  });

  final Duration duration;
  final double gap;
  final Curve curve;

  @override
  State<AnimatedSliverGap> createState() => _AnimatedSliverGapState();
}

class _AnimatedSliverGapState extends State<AnimatedSliverGap> with SingleTickerProviderStateMixin {
  late final _controller = AnimationController(
    vsync: this,
    value: widget.gap,
    upperBound: double.infinity,
  );

  @override
  void didUpdateWidget(covariant AnimatedSliverGap oldWidget) {
    if (oldWidget.gap != widget.gap) {
      _controller.animateTo(
        widget.gap,
        curve: widget.curve,
        duration: widget.duration,
      );
    }
    super.didUpdateWidget(oldWidget);
  }

  @override
  Widget build(BuildContext context) {
    return ValueListenableBuilder<double>(
      valueListenable: _controller,
      builder: (context, gap, _) {
        return SliverGap(gap);
      },
    );
  }
}

class SliverGap extends LeafRenderObjectWidget {
  const SliverGap(this.gap, {Key? key}) : super(key: key);

  final double gap;

  static const size4 = SliverGap(4);
  static const size8 = SliverGap(8);
  static const size16 = SliverGap(16);
  static const size24 = SliverGap(24);
  static const size32 = SliverGap(32);
  static const size64 = SliverGap(64);

  @override
  RenderSliverGap createRenderObject(BuildContext context) => RenderSliverGap(gap);

  @override
  void updateRenderObject(BuildContext context, covariant RenderSliverGap renderObject) {
    renderObject.gap = gap;
    super.updateRenderObject(context, renderObject);
  }
}

class RenderSliverGap extends RenderSliver {
  RenderSliverGap(this._gap) : super() {
    markNeedsLayout();
  }

  double _gap;
  double get gap => _gap;

  set gap(double value) {
    if (_gap != value) {
      _gap = value;
      markNeedsLayout();
    }
  }

  @override
  void performLayout() {
    final cacheExtent = calculateCacheOffset(constraints, from: 0, to: gap);
    final paintExtent = calculatePaintOffset(constraints, from: 0, to: gap);
    geometry = SliverGeometry(
      paintExtent: paintExtent,
      scrollExtent: gap,
      visible: false,
      cacheExtent: cacheExtent,
      maxPaintExtent: gap,
    );
  }
}