flutter-quill/lib/widgets/cursor.dart

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

import 'box.dart';

const Duration _FADE_DURATION = Duration(milliseconds: 250);

class CursorStyle {
  final Color color;
  final Color backgroundColor;
  final double width;
  final double height;
  final Radius radius;
  final Offset offset;
  final bool opacityAnimates;
  final bool paintAboveText;

  const CursorStyle({
    @required this.color,
    @required this.backgroundColor,
    this.width = 1.0,
    this.height,
    this.radius,
    this.offset,
    this.opacityAnimates = false,
    this.paintAboveText = false,
  })  : assert(color != null),
        assert(backgroundColor != null),
        assert(opacityAnimates != null),
        assert(paintAboveText != null);

  @override
  bool operator ==(Object other) =>
      identical(this, other) ||
          other is CursorStyle &&
              runtimeType == other.runtimeType &&
              color == other.color &&
              backgroundColor == other.backgroundColor &&
              width == other.width &&
              height == other.height &&
              radius == other.radius &&
              offset == other.offset &&
              opacityAnimates == other.opacityAnimates &&
              paintAboveText == other.paintAboveText;

  @override
  int get hashCode =>
      color.hashCode ^
      backgroundColor.hashCode ^
      width.hashCode ^
      height.hashCode ^
      radius.hashCode ^
      offset.hashCode ^
      opacityAnimates.hashCode ^
      paintAboveText.hashCode;
}

class CursorCont extends ChangeNotifier {
  final ValueNotifier<bool> show;
  final ValueNotifier<bool> _blink;
  final ValueNotifier<Color> color;
  AnimationController _blinkOpacityCont;
  CursorStyle _style;

  CursorCont({
    @required ValueNotifier<bool> show,
    @required CursorStyle style,
    @required TickerProvider tickerProvider,
  })  : assert(show != null),
        assert(style != null),
        assert(tickerProvider != null),
        show = show ?? ValueNotifier<bool>(false),
        _style = style,
        _blink = ValueNotifier(false),
        color = ValueNotifier(style.color) {
    _blinkOpacityCont =
        AnimationController(vsync: tickerProvider, duration: _FADE_DURATION);
    _blinkOpacityCont.addListener(_onColorTick);
  }

  void _onColorTick() {
    color.value = _style.color.withOpacity(_blinkOpacityCont.value);
    _blink.value = show.value && _blinkOpacityCont.value > 0;
  }
}

class CursorPainter {
  final RenderContentProxyBox editable;
  final CursorStyle style;
  final Rect prototype;
  final Color color;
  final double devicePixelRatio;

  CursorPainter(this.editable, this.style, this.prototype, this.color,
      this.devicePixelRatio);

  paint(Canvas canvas, Offset offset, TextPosition position) {
    assert(prototype != null);

    Offset caretOffset =
        editable.getOffsetForCaret(position, prototype) + offset;
    Rect caretRect = prototype.shift(caretOffset);
    if (style.offset != null) {
      caretRect = caretRect.shift(style.offset);
    }

    if (caretRect.left < 0.0) {
      caretRect = caretRect.shift(Offset(-caretRect.left, 0.0));
    }

    double caretHeight = editable.getFullHeightForCaret(position);
    if (caretHeight != null) {
      switch (defaultTargetPlatform) {
        case TargetPlatform.android:
        case TargetPlatform.fuchsia:
        case TargetPlatform.linux:
        case TargetPlatform.windows:
          caretRect = Rect.fromLTWH(
            caretRect.left,
            caretRect.top - 2.0,
            caretRect.width,
            caretHeight,
          );
          break;
        case TargetPlatform.iOS:
        case TargetPlatform.macOS:
          caretRect = Rect.fromLTWH(
            caretRect.left,
            caretRect.top + (caretHeight - caretRect.height) / 2,
            caretRect.width,
            caretRect.height,
          );
          break;
        default:
          throw UnimplementedError();
      }
    }

    Offset caretPosition = editable.localToGlobal(caretRect.topLeft);
    double pixelMultiple = 1.0 / devicePixelRatio;
    caretRect = caretRect.shift(Offset(
        caretPosition.dx.isFinite
            ? (caretPosition.dx / pixelMultiple).round() * pixelMultiple -
                caretPosition.dx
            : caretPosition.dx,
        caretPosition.dy.isFinite
            ? (caretPosition.dy / pixelMultiple).round() * pixelMultiple -
                caretPosition.dy
            : caretPosition.dy));

    Paint paint = Paint()..color = color;
    if (style.radius == null) {
      canvas.drawRect(caretRect, paint);
      return;
    }

    RRect caretRRect = RRect.fromRectAndRadius(caretRect, style.radius);
    canvas.drawRRect(caretRRect, paint);
  }
}