feat: create GradientSwatch and GradOf

CHANGELOG.md

@@ -7,12 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Add
+
+- `GradOf` class with the constructors `blueGrey`, `grey`, and `brown`.
+- `GradientSwatch` helper abstract class.
+
 ### Changed
 
 - stricter lint rules.
-- improvements in README.
-- Rename 'o' parameter to 'opacity' in `white` and `black` constructors of the
-  `PaletteRGB` class — **BREAKING CHANGES**.
+- improvements to README file.
+- rename 'o' parameter to 'opacity' in `white` and `black` constructors of the
+  `PaletteRGB` class — **BREAKING CHANGE**.
+- rename `GradientImmu` class to `GradientImmut` — **BREAKING CHANGE**.
 
 ### Removed
 

README.md

@@ -194,12 +194,14 @@ region. The colors produced by a gradient vary continuously with position,
 producing smooth color transitions.
 
 While the `Swatch` interface retrieves an `iterable<Colors>` object, subclasses
-of `Gradients` retrieves a `List<Colors>`, which makes them better suited for
+of `Gradient` retrieves a `List<Colors>`, which makes them better suited for
 dealing with Flutter's gradient APIs — these APIs almost always expects a
 `List<Color>` object as a parameter instead of an `Iterable<Color>` object.
 
-An example of a `Gradient` implementation is the abstract class `GradientImmu`,
-which retrieves immutable `List<Colors>` objects.
+For Material Design color gradients, use the `GradOf` class, which in turn
+implements the `Gradient` interface. Another example of a `Gradient`
+implementation is the abstract class `GradientImmu`, which retrieves immutable
+`List<Colors>` objects.
 
 For a complete list of gradients:
 

lib/gradients.dart

@@ -1,7 +1,7 @@
-/// Gradients
-///
 /// Suitable classes for working with Flutter's Gradient Apis.
 library gradients;
 
 export 'src/gradient.dart';
-export 'src/gradient_immu.dart';
+export 'src/gradient_immut.dart';
+export 'src/gradient_swatch.dart';
+export 'src/material/grad_of.dart';

lib/src/gradient.dart

@@ -12,6 +12,8 @@ import 'swatch.dart';
 /// See also:
 /// - [color-gradient](https://en.wikipedia.org/wiki/Color_gradient)
 abstract class Gradient implements Swatch {
+  const Gradient();
+
   /// A list of position-dependent colors — a color gradient.
   @override
   List<Color> get colors;

lib/src/gradient_immut.dart

@@ -0,0 +1,16 @@
+import 'dart:ui';
+
+import 'package:eo_color/src/palette.dart';
+
+import 'gradient.dart';
+import 'swatch_base.dart';
+
+/// Convenience [Gradient] that retrieves an immutable list of colors.
+abstract class GradientImmut extends SwatchBase implements Gradient {
+  /// [palettes] is a source of colors to be transformed into an immutable list.
+  const GradientImmut(Iterable<Palette> palettes) : super(palettes);
+
+  /// An **immutable list** of position-dependent colors — a color gradient.
+  @override
+  List<Color> get colors => List.unmodifiable(super.colors);
+}

lib/src/gradient_swatch.dart

@@ -0,0 +1,20 @@
+import 'dart:ui';
+
+import 'gradient.dart';
+import 'swatch.dart';
+
+/// A [Gradient] from a [Swatch] instance.
+abstract class GradientSwatch implements Gradient {
+  /// A color gradient from a color [Swatch].
+  ///
+  /// [growable] wheather or not to create a list that can grow (expand).
+  const GradientSwatch(Swatch swatch, {bool growable = false})
+      : _swatch = swatch,
+        _growable = growable;
+
+  final Swatch _swatch;
+  final bool _growable;
+
+  @override
+  List<Color> get colors => List.of(_swatch.colors, growable: _growable);
+}

lib/src/material/black/black.dart

@@ -18,20 +18,20 @@ class Black extends PaletteRGB {
   const Black() : super.black();
 
   /// 87% opacity.
-  const Black.opacity87() : super.black(opacity:0xDD);
+  const Black.opacity87() : super.black(opacity: 0xDD);
 
   /// 54% opacity.
-  const Black.opacity54() : super.black(opacity:0x8A);
+  const Black.opacity54() : super.black(opacity: 0x8A);
 
   /// 45% opacity.
-  const Black.opacity45() : super.black(opacity:0x73);
+  const Black.opacity45() : super.black(opacity: 0x73);
 
   /// 38% opacity.
-  const Black.opacity38() : super.black(opacity:0x61);
+  const Black.opacity38() : super.black(opacity: 0x61);
 
   /// 26% opacity.
-  const Black.opacity26() : super.black(opacity:0x42);
+  const Black.opacity26() : super.black(opacity: 0x42);
 
   /// 12% opacity.
-  const Black.opacity12() : super.black(opacity:0x1F);
+  const Black.opacity12() : super.black(opacity: 0x1F);
 }

lib/src/material/blue_grey/blue_grey_grad.dart

@@ -0,0 +1,23 @@
+import 'dart:ui';
+
+import '../../gradient.dart';
+import 'blue_greys.dart';
+
+/// A gradient of ten shades of blue-grey.
+///
+/// See also: [BlueGreys].
+class BlueGreyGrad extends Gradient {
+  /// Ten shades of blue-grey; the higher the index, the darker the color.
+  ///
+  /// Creates a growable list when [growable] is true; otherwise, it returns a
+  /// fixed-length list.
+  ///
+  /// See also: [BlueGreys].
+  const BlueGreyGrad({bool growable = false}) : _growable = growable;
+
+  static const _src = BlueGreys();
+  final bool _growable;
+
+  @override
+  List<Color> get colors => List.of(_src.colors, growable: _growable);
+}

lib/src/material/grad_of.dart

@@ -0,0 +1,26 @@
+import '../../swatches.dart';
+import '../gradient_swatch.dart';
+
+/// The gradient of the shades of a Material Design color.
+///
+/// It produces a list of colors of fixed or growable length, ordered by the
+/// darkness of the colors: the higher the index, the darker the color.
+class GradOf extends GradientSwatch {
+  /// A gradient of ten shades of blue-grey.
+  ///
+  /// See also: [BlueGreys].
+  const GradOf.blueGrey({bool growable = false})
+      : super(const BlueGreys(), growable: growable);
+
+  /// A gradient of ten shades of brown.
+  ///
+  /// See also: [Browns].
+  const GradOf.brown({bool growable = false})
+      : super(const Browns(), growable: growable);
+
+  /// A gradient of ten shades of grey.
+  ///
+  /// See also: [Greys].
+  const GradOf.grey({bool growable = false})
+      : super(const Greys(), growable: growable);
+}

lib/src/material/white/white.dart

@@ -20,26 +20,26 @@ class White extends PaletteRGB {
   const White() : super.white();
 
   /// 70% opacity.
-  const White.opacity70() : super.white(opacity:0xB3);
+  const White.opacity70() : super.white(opacity: 0xB3);
 
   /// 60% opacity.
-  const White.opacity60() : super.white(opacity:0x99);
+  const White.opacity60() : super.white(opacity: 0x99);
 
   /// 54% opacity.
-  const White.opacity54() : super.white(opacity:0x8A);
+  const White.opacity54() : super.white(opacity: 0x8A);
 
   /// 38% opacity.
-  const White.opacity38() : super.white(opacity:0x62);
+  const White.opacity38() : super.white(opacity: 0x62);
 
   /// 30% opacity.
-  const White.opacity30() : super.white(opacity:0x4D);
+  const White.opacity30() : super.white(opacity: 0x4D);
 
   /// 24% opacity.
-  const White.opacity24() : super.white(opacity:0x3D);
+  const White.opacity24() : super.white(opacity: 0x3D);
 
   /// 12% opacity.
-  const White.opacity12() : super.white(opacity:0x1F);
+  const White.opacity12() : super.white(opacity: 0x1F);
 
   /// 10% opacity.
-  const White.opacity10() : super.white(opacity:0x1A);
+  const White.opacity10() : super.white(opacity: 0x1A);
 }

lib/src/palette_rgb.dart

@@ -22,12 +22,14 @@ abstract class PaletteRGB implements Palette {
   /// Convenience white #FFFFFF.
   ///
   /// [opacity] the opacity value; it defaults to 0xFF - fully opaque.
-  const PaletteRGB.white({int opacity = 0xFF}) : this(alpha: opacity, rgb: 0xFFFFFF);
+  const PaletteRGB.white({int opacity = 0xFF})
+      : this(alpha: opacity, rgb: 0xFFFFFF);
 
   /// Convenience black #000000.
   ///
   /// [opacity] the opacity value; it defaults to 0xFF - fully opaque.
-  const PaletteRGB.black({int opacity = 0xFF}) : this(alpha: opacity, rgb: 0x000000);
+  const PaletteRGB.black({int opacity = 0xFF})
+      : this(alpha: opacity, rgb: 0x000000);
 
   /// the color's 32 bits.
   final int _value;

lib/src/swatch.dart

@@ -5,6 +5,9 @@ import 'dart:ui';
 /// A group of related colors such as the colors of the rainbow, shades of grey,
 /// etc.
 abstract class Swatch {
+  /// const ctor.
+  const Swatch();
+
   /// The colors.
   ///
   /// The order of the colors varies between swatches. Some swatches might order

test/gradient_immu_test.dart → test/gradient_immut_test.dart

@@ -1,4 +1,6 @@
-import 'package:eo_color/eo_color.dart';
+import 'package:eo_color/src/gradient_immut.dart';
+import 'package:eo_color/src/material/grey/grey.dart';
+import 'package:eo_color/src/material/transparent.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 const aGrey = [Grey()];
@@ -10,7 +12,7 @@ const manyGreys = [
   Grey.dark(),
 ];
 
-class GradTest extends GradientImmu {
+class GradTest extends GradientImmut {
   const GradTest.empty() : super(const []);
   const GradTest.single() : super(aGrey);
   const GradTest.many() : super(manyGreys);

test/material/grad_of_test.dart

@@ -0,0 +1,58 @@
+import 'package:eo_color/src/material/blue_grey/blue_greys.dart';
+import 'package:eo_color/src/material/brown/browns.dart';
+import 'package:eo_color/src/material/grad_of.dart';
+import 'package:eo_color/src/material/grey/greys.dart';
+import 'package:eo_color/src/material/transparent.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('GradOf', () {
+    final aColor = const Transparent().color;
+    group('blueGrey:', () {
+      final blueGreyGrad = const GradOf.blueGrey().colors;
+      test('gradient', () {
+        expect(blueGreyGrad, List.of(const BlueGreys().colors));
+      });
+      test('fixed-length list', () {
+        /// Should not support adding colors to the list.
+        expect(() => blueGreyGrad.add(aColor), throwsUnsupportedError);
+      });
+      test('growable list', () {
+        final growable = const GradOf.blueGrey(growable: true).colors;
+        final prevLength = growable.length;
+        growable.add(aColor);
+        expect(growable.length, prevLength + 1);
+      });
+    });
+    group('grey:', () {
+      final greyGrad = const GradOf.grey().colors;
+      test('gradient', () {
+        expect(greyGrad, List.of(const Greys().colors));
+      });
+      test('fixed-length list', () {
+        expect(() => greyGrad.add(aColor), throwsUnsupportedError);
+      });
+      test('growable list', () {
+        final growable = const GradOf.grey(growable: true).colors;
+        final prevLength = growable.length;
+        growable.add(aColor);
+        expect(growable.length, prevLength + 1);
+      });
+    });
+    group('brown:', () {
+      final brownGrad = const GradOf.brown().colors;
+      test('gradient', () {
+        expect(brownGrad, List.of(const Browns().colors));
+      });
+      test('fixed-length list', () {
+        expect(() => brownGrad.add(aColor), throwsUnsupportedError);
+      });
+      test('growable list', () {
+        final growable = const GradOf.brown(growable: true).colors;
+        final prevLength = growable.length;
+        growable.add(aColor);
+        expect(growable.length, prevLength + 1);
+      });
+    });
+  });
+}