icon_theme_data.dart 4 KB
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// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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import 'dart:ui' show Color, hashValues;
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import 'dart:ui' as ui show lerpDouble;
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import 'package:flutter/foundation.dart';

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/// Defines the color, opacity, and size of icons.
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///
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/// Used by [IconTheme] to control the color, opacity, and size of icons in a
/// widget subtree.
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///
/// To obtain the current icon theme, use [IconTheme.of]. To convert an icon
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/// theme to a version with all the fields filled in, use [new
/// IconThemeData.fallback].
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class IconThemeData extends Diagnosticable {
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  /// Creates an icon theme data.
  ///
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  /// The opacity applies to both explicit and default icon colors. The value
  /// is clamped between 0.0 and 1.0.
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  const IconThemeData({this.color, double opacity, this.size}) : _opacity = opacity;
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  /// Creates an icon them with some reasonable default values.
  ///
  /// The [color] is black, the [opacity] is 1.0, and the [size] is 24.0.
  const IconThemeData.fallback()
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      : color = const Color(0xFF000000),
        _opacity = 1.0,
        size = 24.0;
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  /// Creates a copy of this icon theme but with the given fields replaced with
  /// the new values.
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  IconThemeData copyWith({Color color, double opacity, double size}) {
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    return new IconThemeData(
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      color: color ?? this.color,
      opacity: opacity ?? this.opacity,
      size: size ?? this.size,
    );
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  }

  /// Returns a new icon theme that matches this icon theme but with some values
  /// replaced by the non-null parameters of the given icon theme. If the given
  /// icon theme is null, simply returns this icon theme.
  IconThemeData merge(IconThemeData other) {
    if (other == null)
      return this;
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    return copyWith(
      color: other.color,
      opacity: other.opacity,
      size: other.size,
    );
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  }

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  /// Whether all the properties of this object are non-null.
  bool get isConcrete => color != null && opacity != null && size != null;
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  /// The default color for icons.
  final Color color;

  /// An opacity to apply to both explicit and default icon colors.
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  double get opacity => _opacity?.clamp(0.0, 1.0);
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  final double _opacity;
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  /// The default size for icons.
  final double size;

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  /// Linearly interpolate between two icon theme data objects.
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  ///
  /// The `t` argument represents position on the timeline, with 0.0 meaning
  /// that the interpolation has not started, returning `a` (or something
  /// equivalent to `a`), 1.0 meaning that the interpolation has finished,
  /// returning `b` (or something equivalent to `b`), and values in between
  /// meaning that the interpolation is at the relevant point on the timeline
  /// between `a` and `b`. The interpolation can be extrapolated beyond 0.0 and
  /// 1.0, so negative values and values greater than 1.0 are valid (and can
  /// easily be generated by curves such as [Curves.elasticInOut]).
  ///
  /// Values for `t` are usually obtained from an [Animation<double>], such as
  /// an [AnimationController].
  static IconThemeData lerp(IconThemeData a, IconThemeData b, double t) {
    assert(t != null);
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    return new IconThemeData(
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      color: Color.lerp(a.color, b.color, t),
      opacity: ui.lerpDouble(a.opacity, b.opacity, t),
      size: ui.lerpDouble(a.size, b.size, t),
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    );
  }

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  @override
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  bool operator ==(dynamic other) {
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    if (other.runtimeType != runtimeType)
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      return false;
    final IconThemeData typedOther = other;
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    return color == typedOther.color
        && opacity == typedOther.opacity
        && size == typedOther.size;
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  }

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  @override
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  int get hashCode => hashValues(color, opacity, size);
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  @override
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  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(new DiagnosticsProperty<Color>('color', color, defaultValue: null));
    properties.add(new DoubleProperty('opacity', opacity, defaultValue: null));
    properties.add(new DoubleProperty('size', size, defaultValue: null));
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  }
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}