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Factor out LinearGradient and RadialGradient (#12155)

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Ian Hickson 2017-09-20 13:41:20 -07:00 committed by GitHub
parent 8e5ec0b153
commit 61a2492a5a
6 changed files with 422 additions and 412 deletions
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1
packages/flutter/lib/painting.dart
View file

@ -27,6 +27,7 @@ export 'src/painting/decoration.dart';
export 'src/painting/edge_insets.dart';
export 'src/painting/flutter_logo.dart';
export 'src/painting/fractional_offset.dart';
export 'src/painting/gradient.dart';
export 'src/painting/text_painter.dart';
export 'src/painting/text_span.dart';
export 'src/painting/text_style.dart';

3
packages/flutter/lib/src/painting/border.dart
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@ -8,11 +8,8 @@ import 'package:flutter/foundation.dart';
import 'basic_types.dart';
import 'border_radius.dart';
import 'decoration.dart';
import 'edge_insets.dart';
export 'edge_insets.dart' show EdgeInsets;
/// The shape to use when rendering a [Border] or [BoxDecoration].
enum BoxShape {
/// An axis-aligned, 2D rectangle. May have rounded corners (described by a

408
packages/flutter/lib/src/painting/box_painter.dart
View file

@ -3,7 +3,7 @@
// found in the LICENSE file.
import 'dart:math' as math;
import 'dart:ui' as ui show Image, Gradient, lerpDouble;
import 'dart:ui' as ui show Image, lerpDouble;
import 'package:flutter/foundation.dart';
import 'package:flutter/services.dart';
@ -15,8 +15,7 @@ import 'box_fit.dart';
import 'decoration.dart';
import 'edge_insets.dart';
import 'fractional_offset.dart';
export 'edge_insets.dart' show EdgeInsets;
import 'gradient.dart';
/// A shadow cast by a box.
///
@ -133,409 +132,6 @@ class BoxShadow {
String toString() => 'BoxShadow($color, $offset, $blurRadius, $spreadRadius)';
}
/// A 2D gradient.
///
/// This is an interface that allows [LinearGradient] and [RadialGradient]
/// classes to be used interchangeably in [BoxDecoration]s.
@immutable
abstract class Gradient {
/// Abstract const constructor. This constructor enables subclasses to provide
/// const constructors so that they can be used in const expressions.
const Gradient();
/// Creates a [Shader] for this gradient to fill the given rect.
Shader createShader(Rect rect);
}
/// A 2D linear gradient.
///
/// This class is used by [BoxDecoration] to represent gradients. This abstracts
/// out the arguments to the [new ui.Gradient.linear] constructor from the
/// `dart:ui` library.
///
/// A gradient has two anchor points, [begin] and [end]. The [begin] point
/// corresponds to 0.0, and the [end] point corresponds to 1.0. These points are
/// expressed in fractions, so that the same gradient can be reused with varying
/// sized boxes without changing the parameters. (This contrasts with [new
/// ui.Gradient.linear], whose arguments are expressed in logical pixels.)
///
/// The [colors] are described by a list of [Color] objects. There must be at
/// least two colors. If there are more than two, a [stops] list must be
/// provided. It must have the same length as [colors], and specifies the
/// position of each color stop between 0.0 and 1.0.
///
/// The region of the canvas before [begin] and after [end] is colored according
/// to [tileMode].
///
/// Typically this class is used with [BoxDecoration], which does the painting.
/// To use a [LinearGradient] to paint on a canvas directly, see [createShader].
///
/// ## Sample code
///
/// This sample draws a picture that looks like vertical window shades by having
/// a [Container] display a [BoxDecoration] with a [LinearGradient].
///
/// ```dart
/// new Container(
/// decoration: new BoxDecoration(
/// gradient: new LinearGradient(
/// begin: FractionalOffset.topLeft,
/// end: new FractionalOffset(0.1, 0.0), // 10% of the width, so there are ten blinds.
/// colors: [const Color(0xFFFFFFEE), const Color(0xFF999999)], // whitish to gray
/// tileMode: TileMode.repeated, // repeats the gradient over the canvas
/// ),
/// ),
/// )
/// ```
///
/// See also:
///
/// * [RadialGradient], which displays a gradient in concentric circles, and
/// has an example which shows a different way to use [Gradient] objects.
/// * [BoxDecoration], which can take a [LinearGradient] in its
/// [BoxDecoration.gradient] property.
class LinearGradient extends Gradient {
/// Creates a linear graident.
///
/// The [colors] argument must not be null. If [stops] is non-null, it must
/// have the same length as [colors].
const LinearGradient({
this.begin: FractionalOffset.centerLeft,
this.end: FractionalOffset.centerRight,
@required this.colors,
this.stops,
this.tileMode: TileMode.clamp,
}) : assert(begin != null),
assert(end != null),
assert(colors != null),
assert(tileMode != null);
/// The offset from coordinate (0.0,0.0) at which stop 0.0 of the
/// gradient is placed, in a coordinate space that maps the top left
/// of the paint box at (0.0,0.0) and the bottom right at (1.0,1.0).
///
/// For example, a begin offset of (0.0,0.5) is half way down the
/// left side of the box.
final FractionalOffset begin;
/// The offset from coordinate (0.0,0.0) at which stop 1.0 of the
/// gradient is placed, in a coordinate space that maps the top left
/// of the paint box at (0.0,0.0) and the bottom right at (1.0,1.0).
///
/// For example, an end offset of (1.0,0.5) is half way down the
/// right side of the box.
final FractionalOffset end;
/// The colors the gradient should obtain at each of the stops.
///
/// If [stops] is non-null, this list must have the same length as [stops]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// This list must have at least two colors in it (otherwise, it's not a
/// gradient!).
final List<Color> colors;
/// A list of values from 0.0 to 1.0 that denote fractions of the vector from
/// start to end.
///
/// If non-null, this list must have the same length as [colors]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// If the first value is not 0.0, then a stop with position 0.0 and a color
/// equal to the first color in [colors] is implied.
///
/// If the last value is not 1.0, then a stop with position 1.0 and a color
/// equal to the last color in [colors] is implied.
///
/// The values in the [stops] list must be in ascending order. If a value in
/// the [stops] list is less than an earlier value in the list, then its value
/// is assumed to equal the previous value.
final List<double> stops;
/// How this gradient should tile the plane beyond in the region before
/// [begin] and after [end].
///
/// For details, see [TileMode].
///
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_clamp_linear.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_mirror_linear.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_repeated_linear.png)
final TileMode tileMode;
@override
Shader createShader(Rect rect) {
return new ui.Gradient.linear(
begin.withinRect(rect),
end.withinRect(rect),
colors, stops, tileMode,
);
}
/// Returns a new [LinearGradient] with its properties scaled by the given
/// factor.
LinearGradient scale(double factor) {
return new LinearGradient(
begin: begin,
end: end,
colors: colors.map<Color>((Color color) => Color.lerp(null, color, factor)).toList(),
stops: stops,
tileMode: tileMode,
);
}
/// Linearly interpolate between two [LinearGradient]s.
///
/// If either gradient is null, this function linearly interpolates from a
/// a gradient that matches the other gradient in [begin], [end], [stops] and
/// [tileMode] and with the same [colors] but transparent.
///
/// If neither gradient is null, they must have the same number of [colors].
static LinearGradient lerp(LinearGradient a, LinearGradient b, double t) {
if (a == null && b == null)
return null;
if (a == null)
return b.scale(t);
if (b == null)
return a.scale(1.0 - t);
// Interpolation is only possible when the lengths of colors and stops are
// the same or stops is null for one.
// TODO(xster): lerp unsimilar LinearGradients in the future by scaling
// lists of LinearGradients.
assert(a.colors.length == b.colors.length);
assert(a.stops == null || b.stops == null || a.stops.length == b.stops.length);
final List<Color> interpolatedColors = <Color>[];
for (int i = 0; i < a.colors.length; i += 1)
interpolatedColors.add(Color.lerp(a.colors[i], b.colors[i], t));
List<double> interpolatedStops;
if (a.stops != null && b.stops != null) {
for (int i = 0; i < a.stops.length; i += 1)
interpolatedStops.add(ui.lerpDouble(a.stops[i], b.stops[i], t));
} else {
interpolatedStops = a.stops ?? b.stops;
}
return new LinearGradient(
begin: FractionalOffset.lerp(a.begin, b.begin, t),
end: FractionalOffset.lerp(a.end, b.end, t),
colors: interpolatedColors,
stops: interpolatedStops,
tileMode: t < 0.5 ? a.tileMode : b.tileMode,
);
}
@override
bool operator ==(dynamic other) {
if (identical(this, other))
return true;
if (runtimeType != other.runtimeType)
return false;
final LinearGradient typedOther = other;
if (begin != typedOther.begin ||
end != typedOther.end ||
tileMode != typedOther.tileMode ||
colors?.length != typedOther.colors?.length ||
stops?.length != typedOther.stops?.length)
return false;
if (colors != null) {
assert(typedOther.colors != null);
assert(colors.length == typedOther.colors.length);
for (int i = 0; i < colors.length; i += 1) {
if (colors[i] != typedOther.colors[i])
return false;
}
}
if (stops != null) {
assert(typedOther.stops != null);
assert(stops.length == typedOther.stops.length);
for (int i = 0; i < stops.length; i += 1) {
if (stops[i] != typedOther.stops[i])
return false;
}
}
return true;
}
@override
int get hashCode => hashValues(begin, end, tileMode, hashList(colors), hashList(stops));
@override
String toString() {
return 'LinearGradient($begin, $end, $colors, $stops, $tileMode)';
}
}
/// A 2D radial gradient.
///
/// This class is used by [BoxDecoration] to represent gradients. This abstracts
/// out the arguments to the [new ui.Gradient.radial] constructor from the
/// `dart:ui` library.
///
/// A gradient has a [center] and a [radius]. The [center] point corresponds to
/// 0.0, and the ring at [radius] from the center corresponds to 1.0. These
/// lengths are expressed in fractions, so that the same gradient can be reused
/// with varying sized boxes without changing the parameters. (This contrasts
/// with [new ui.Gradient.radial], whose arguments are expressed in logical
/// pixels.)
///
/// The [colors] are described by a list of [Color] objects. There must be at
/// least two colors. If there are more than two, a [stops] list must be
/// provided. It must have the same length as [colors], and specifies the
/// position of each color stop between 0.0 and 1.0.
///
/// The region of the canvas beyond [radius] from the [center] is colored
/// according to [tileMode].
///
/// Typically this class is used with [BoxDecoration], which does the painting.
/// To use a [RadialGradient] to paint on a canvas directly, see [createShader].
///
/// ## Sample code
///
/// This function draws a gradient that looks like a sun in a blue sky.
///
/// ```dart
/// void paintSky(Canvas canvas, Rect rect) {
/// var gradient = new RadialGradient(
/// center: const FractionalOffset(0.7, 0.2), // near the top right
/// radius: 0.2,
/// colors: [
/// const Color(0xFFFFFF00), // yellow sun
/// const Color(0xFF0099FF), // blue sky
/// ],
/// stops: [0.4, 1.0],
/// );
/// // rect is the area we are painting over
/// var paint = new Paint()
/// ..shader = gradient.createShader(rect);
/// canvas.drawRect(rect, paint);
/// }
/// ```
///
/// See also:
///
/// * [LinearGradient], which displays a gradient in parallel lines, and has an
/// example which shows a different way to use [Gradient] objects.
/// * [BoxDecoration], which can take a [RadialGradient] in its
/// [BoxDecoration.gradient] property.
/// * [CustomPainter], which shows how to use the above sample code in a custom
/// painter.
class RadialGradient extends Gradient {
/// Creates a radial gradient.
///
/// The [colors] argument must not be null. If [stops] is non-null, it must
/// have the same length as [colors].
const RadialGradient({
this.center: FractionalOffset.center,
this.radius: 0.5,
@required this.colors,
this.stops,
this.tileMode: TileMode.clamp,
}) : assert(center != null),
assert(radius != null),
assert(colors != null),
assert(tileMode != null);
/// The center of the gradient, as an offset into the unit square
/// describing the gradient which will be mapped onto the paint box.
///
/// For example, an offset of (0.5,0.5) will place the radial
/// gradient in the center of the box.
final FractionalOffset center;
/// The radius of the gradient, as a fraction of the shortest side
/// of the paint box.
///
/// For example, if a radial gradient is painted on a box that is
/// 100.0 pixels wide and 200.0 pixels tall, then a radius of 1.0
/// will place the 1.0 stop at 100.0 pixels from the [center].
final double radius;
/// The colors the gradient should obtain at each of the stops.
///
/// If [stops] is non-null, this list must have the same length as [stops]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// This list must have at least two colors in it (otherwise, it's not a
/// gradient!).
final List<Color> colors;
/// A list of values from 0.0 to 1.0 that denote concentric rings.
///
/// The rings are centered at [center] and have a radius equal to the value of
/// the stop times [radius].
///
/// If non-null, this list must have the same length as [colors]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// If the first value is not 0.0, then a stop with position 0.0 and a color
/// equal to the first color in [colors] is implied.
///
/// If the last value is not 1.0, then a stop with position 1.0 and a color
/// equal to the last color in [colors] is implied.
///
/// The values in the [stops] list must be in ascending order. If a value in
/// the [stops] list is less than an earlier value in the list, then its value
/// is assumed to equal the previous value.
final List<double> stops;
/// How this gradient should tile the plane beyond the outer ring at [radius]
/// pixels from the [center].
///
/// For details, see [TileMode].
///
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_clamp_radial.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_mirror_radial.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_repeated_radial.png)
final TileMode tileMode;
@override
Shader createShader(Rect rect) {
return new ui.Gradient.radial(
center.withinRect(rect),
radius * rect.shortestSide,
colors, stops, tileMode
);
}
@override
bool operator ==(dynamic other) {
if (identical(this, other))
return true;
if (runtimeType != other.runtimeType)
return false;
final RadialGradient typedOther = other;
if (center != typedOther.center ||
radius != typedOther.radius ||
tileMode != typedOther.tileMode ||
colors?.length != typedOther.colors?.length ||
stops?.length != typedOther.stops?.length)
return false;
if (colors != null) {
assert(typedOther.colors != null);
assert(colors.length == typedOther.colors.length);
for (int i = 0; i < colors.length; i += 1) {
if (colors[i] != typedOther.colors[i])
return false;
}
}
if (stops != null) {
assert(typedOther.stops != null);
assert(stops.length == typedOther.stops.length);
for (int i = 0; i < stops.length; i += 1) {
if (stops[i] != typedOther.stops[i])
return false;
}
}
return true;
}
@override
int get hashCode => hashValues(center, radius, tileMode, hashList(colors), hashList(stops));
@override
String toString() {
return 'RadialGradient($center, $radius, $colors, $stops, $tileMode)';
}
}
/// How to paint any portions of a box not covered by an image.
enum ImageRepeat {
/// Repeat the image in both the x and y directions until the box is filled.

3
packages/flutter/lib/src/painting/decoration.dart
View file

@ -10,9 +10,6 @@ import 'edge_insets.dart';
export 'package:flutter/services.dart' show ImageConfiguration;
export 'basic_types.dart' show Offset, Size;
export 'edge_insets.dart' show EdgeInsets;
// This group of classes is intended for painting in cartesian coordinates.
/// A description of a box decoration (a decoration applied to a [Rect]).

1
packages/flutter/lib/src/painting/flutter_logo.dart
View file

@ -12,6 +12,7 @@ import 'package:flutter/foundation.dart';
import 'basic_types.dart';
import 'box_fit.dart';
import 'decoration.dart';
import 'edge_insets.dart';
import 'fractional_offset.dart';
import 'text_painter.dart';
import 'text_span.dart';

418
packages/flutter/lib/src/painting/gradient.dart Normal file
View file

@ -0,0 +1,418 @@
// 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.
import 'dart:ui' as ui show Gradient, lerpDouble;
import 'package:flutter/foundation.dart';
import 'basic_types.dart';
import 'fractional_offset.dart';
/// A 2D gradient.
///
/// This is an interface that allows [LinearGradient] and [RadialGradient]
/// classes to be used interchangeably in [BoxDecoration]s.
///
/// See also:
///
/// * [dart:ui.Gradient], the class in the [dart:ui] library that is
/// encapsulated by this class and its subclasses.
@immutable
abstract class Gradient {
/// Abstract const constructor. This constructor enables subclasses to provide
/// const constructors so that they can be used in const expressions.
const Gradient();
/// Creates a [Shader] for this gradient to fill the given rect.
Shader createShader(Rect rect);
}
/// A 2D linear gradient.
///
/// This class is used by [BoxDecoration] to represent gradients. This abstracts
/// out the arguments to the [new ui.Gradient.linear] constructor from the
/// `dart:ui` library.
///
/// A gradient has two anchor points, [begin] and [end]. The [begin] point
/// corresponds to 0.0, and the [end] point corresponds to 1.0. These points are
/// expressed in fractions, so that the same gradient can be reused with varying
/// sized boxes without changing the parameters. (This contrasts with [new
/// ui.Gradient.linear], whose arguments are expressed in logical pixels.)
///
/// The [colors] are described by a list of [Color] objects. There must be at
/// least two colors. If there are more than two, a [stops] list must be
/// provided. It must have the same length as [colors], and specifies the
/// position of each color stop between 0.0 and 1.0.
///
/// The region of the canvas before [begin] and after [end] is colored according
/// to [tileMode].
///
/// Typically this class is used with [BoxDecoration], which does the painting.
/// To use a [LinearGradient] to paint on a canvas directly, see [createShader].
///
/// ## Sample code
///
/// This sample draws a picture that looks like vertical window shades by having
/// a [Container] display a [BoxDecoration] with a [LinearGradient].
///
/// ```dart
/// new Container(
/// decoration: new BoxDecoration(
/// gradient: new LinearGradient(
/// begin: FractionalOffset.topLeft,
/// end: new FractionalOffset(0.1, 0.0), // 10% of the width, so there are ten blinds.
/// colors: [const Color(0xFFFFFFEE), const Color(0xFF999999)], // whitish to gray
/// tileMode: TileMode.repeated, // repeats the gradient over the canvas
/// ),
/// ),
/// )
/// ```
///
/// See also:
///
/// * [RadialGradient], which displays a gradient in concentric circles, and
/// has an example which shows a different way to use [Gradient] objects.
/// * [BoxDecoration], which can take a [LinearGradient] in its
/// [BoxDecoration.gradient] property.
class LinearGradient extends Gradient {
/// Creates a linear graident.
///
/// The [colors] argument must not be null. If [stops] is non-null, it must
/// have the same length as [colors].
const LinearGradient({
this.begin: FractionalOffset.centerLeft,
this.end: FractionalOffset.centerRight,
@required this.colors,
this.stops,
this.tileMode: TileMode.clamp,
}) : assert(begin != null),
assert(end != null),
assert(colors != null),
assert(tileMode != null);
/// The offset from coordinate (0.0,0.0) at which stop 0.0 of the
/// gradient is placed, in a coordinate space that maps the top left
/// of the paint box at (0.0,0.0) and the bottom right at (1.0,1.0).
///
/// For example, a begin offset of (0.0,0.5) is half way down the
/// left side of the box.
final FractionalOffset begin;
/// The offset from coordinate (0.0,0.0) at which stop 1.0 of the
/// gradient is placed, in a coordinate space that maps the top left
/// of the paint box at (0.0,0.0) and the bottom right at (1.0,1.0).
///
/// For example, an end offset of (1.0,0.5) is half way down the
/// right side of the box.
final FractionalOffset end;
/// The colors the gradient should obtain at each of the stops.
///
/// If [stops] is non-null, this list must have the same length as [stops]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// This list must have at least two colors in it (otherwise, it's not a
/// gradient!).
final List<Color> colors;
/// A list of values from 0.0 to 1.0 that denote fractions of the vector from
/// start to end.
///
/// If non-null, this list must have the same length as [colors]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// If the first value is not 0.0, then a stop with position 0.0 and a color
/// equal to the first color in [colors] is implied.
///
/// If the last value is not 1.0, then a stop with position 1.0 and a color
/// equal to the last color in [colors] is implied.
///
/// The values in the [stops] list must be in ascending order. If a value in
/// the [stops] list is less than an earlier value in the list, then its value
/// is assumed to equal the previous value.
final List<double> stops;
/// How this gradient should tile the plane beyond in the region before
/// [begin] and after [end].
///
/// For details, see [TileMode].
///
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_clamp_linear.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_mirror_linear.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_repeated_linear.png)
final TileMode tileMode;
@override
Shader createShader(Rect rect) {
return new ui.Gradient.linear(
begin.withinRect(rect),
end.withinRect(rect),
colors, stops, tileMode,
);
}
/// Returns a new [LinearGradient] with its properties scaled by the given
/// factor.
LinearGradient scale(double factor) {
return new LinearGradient(
begin: begin,
end: end,
colors: colors.map<Color>((Color color) => Color.lerp(null, color, factor)).toList(),
stops: stops,
tileMode: tileMode,
);
}
/// Linearly interpolate between two [LinearGradient]s.
///
/// If either gradient is null, this function linearly interpolates from a
/// a gradient that matches the other gradient in [begin], [end], [stops] and
/// [tileMode] and with the same [colors] but transparent.
///
/// If neither gradient is null, they must have the same number of [colors].
static LinearGradient lerp(LinearGradient a, LinearGradient b, double t) {
if (a == null && b == null)
return null;
if (a == null)
return b.scale(t);
if (b == null)
return a.scale(1.0 - t);
// Interpolation is only possible when the lengths of colors and stops are
// the same or stops is null for one.
// TODO(xster): lerp unsimilar LinearGradients in the future by scaling
// lists of LinearGradients.
assert(a.colors.length == b.colors.length);
assert(a.stops == null || b.stops == null || a.stops.length == b.stops.length);
final List<Color> interpolatedColors = <Color>[];
for (int i = 0; i < a.colors.length; i += 1)
interpolatedColors.add(Color.lerp(a.colors[i], b.colors[i], t));
List<double> interpolatedStops;
if (a.stops != null && b.stops != null) {
for (int i = 0; i < a.stops.length; i += 1)
interpolatedStops.add(ui.lerpDouble(a.stops[i], b.stops[i], t));
} else {
interpolatedStops = a.stops ?? b.stops;
}
return new LinearGradient(
begin: FractionalOffset.lerp(a.begin, b.begin, t),
end: FractionalOffset.lerp(a.end, b.end, t),
colors: interpolatedColors,
stops: interpolatedStops,
tileMode: t < 0.5 ? a.tileMode : b.tileMode,
);
}
@override
bool operator ==(dynamic other) {
if (identical(this, other))
return true;
if (runtimeType != other.runtimeType)
return false;
final LinearGradient typedOther = other;
if (begin != typedOther.begin ||
end != typedOther.end ||
tileMode != typedOther.tileMode ||
colors?.length != typedOther.colors?.length ||
stops?.length != typedOther.stops?.length)
return false;
if (colors != null) {
assert(typedOther.colors != null);
assert(colors.length == typedOther.colors.length);
for (int i = 0; i < colors.length; i += 1) {
if (colors[i] != typedOther.colors[i])
return false;
}
}
if (stops != null) {
assert(typedOther.stops != null);
assert(stops.length == typedOther.stops.length);
for (int i = 0; i < stops.length; i += 1) {
if (stops[i] != typedOther.stops[i])
return false;
}
}
return true;
}
@override
int get hashCode => hashValues(begin, end, tileMode, hashList(colors), hashList(stops));
@override
String toString() {
return 'LinearGradient($begin, $end, $colors, $stops, $tileMode)';
}
}
/// A 2D radial gradient.
///
/// This class is used by [BoxDecoration] to represent gradients. This abstracts
/// out the arguments to the [new ui.Gradient.radial] constructor from the
/// `dart:ui` library.
///
/// A gradient has a [center] and a [radius]. The [center] point corresponds to
/// 0.0, and the ring at [radius] from the center corresponds to 1.0. These
/// lengths are expressed in fractions, so that the same gradient can be reused
/// with varying sized boxes without changing the parameters. (This contrasts
/// with [new ui.Gradient.radial], whose arguments are expressed in logical
/// pixels.)
///
/// The [colors] are described by a list of [Color] objects. There must be at
/// least two colors. If there are more than two, a [stops] list must be
/// provided. It must have the same length as [colors], and specifies the
/// position of each color stop between 0.0 and 1.0.
///
/// The region of the canvas beyond [radius] from the [center] is colored
/// according to [tileMode].
///
/// Typically this class is used with [BoxDecoration], which does the painting.
/// To use a [RadialGradient] to paint on a canvas directly, see [createShader].
///
/// ## Sample code
///
/// This function draws a gradient that looks like a sun in a blue sky.
///
/// ```dart
/// void paintSky(Canvas canvas, Rect rect) {
/// var gradient = new RadialGradient(
/// center: const FractionalOffset(0.7, 0.2), // near the top right
/// radius: 0.2,
/// colors: [
/// const Color(0xFFFFFF00), // yellow sun
/// const Color(0xFF0099FF), // blue sky
/// ],
/// stops: [0.4, 1.0],
/// );
/// // rect is the area we are painting over
/// var paint = new Paint()
/// ..shader = gradient.createShader(rect);
/// canvas.drawRect(rect, paint);
/// }
/// ```
///
/// See also:
///
/// * [LinearGradient], which displays a gradient in parallel lines, and has an
/// example which shows a different way to use [Gradient] objects.
/// * [BoxDecoration], which can take a [RadialGradient] in its
/// [BoxDecoration.gradient] property.
/// * [CustomPainter], which shows how to use the above sample code in a custom
/// painter.
class RadialGradient extends Gradient {
/// Creates a radial gradient.
///
/// The [colors] argument must not be null. If [stops] is non-null, it must
/// have the same length as [colors].
const RadialGradient({
this.center: FractionalOffset.center,
this.radius: 0.5,
@required this.colors,
this.stops,
this.tileMode: TileMode.clamp,
}) : assert(center != null),
assert(radius != null),
assert(colors != null),
assert(tileMode != null);
/// The center of the gradient, as an offset into the unit square
/// describing the gradient which will be mapped onto the paint box.
///
/// For example, an offset of (0.5,0.5) will place the radial
/// gradient in the center of the box.
final FractionalOffset center;
/// The radius of the gradient, as a fraction of the shortest side
/// of the paint box.
///
/// For example, if a radial gradient is painted on a box that is
/// 100.0 pixels wide and 200.0 pixels tall, then a radius of 1.0
/// will place the 1.0 stop at 100.0 pixels from the [center].
final double radius;
/// The colors the gradient should obtain at each of the stops.
///
/// If [stops] is non-null, this list must have the same length as [stops]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// This list must have at least two colors in it (otherwise, it's not a
/// gradient!).
final List<Color> colors;
/// A list of values from 0.0 to 1.0 that denote concentric rings.
///
/// The rings are centered at [center] and have a radius equal to the value of
/// the stop times [radius].
///
/// If non-null, this list must have the same length as [colors]. If
/// [colors] has more than two colors, [stops] must be non-null.
///
/// If the first value is not 0.0, then a stop with position 0.0 and a color
/// equal to the first color in [colors] is implied.
///
/// If the last value is not 1.0, then a stop with position 1.0 and a color
/// equal to the last color in [colors] is implied.
///
/// The values in the [stops] list must be in ascending order. If a value in
/// the [stops] list is less than an earlier value in the list, then its value
/// is assumed to equal the previous value.
final List<double> stops;
/// How this gradient should tile the plane beyond the outer ring at [radius]
/// pixels from the [center].
///
/// For details, see [TileMode].
///
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_clamp_radial.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_mirror_radial.png)
/// ![](https://flutter.github.io/assets-for-api-docs/dart-ui/tile_mode_repeated_radial.png)
final TileMode tileMode;
@override
Shader createShader(Rect rect) {
return new ui.Gradient.radial(
center.withinRect(rect),
radius * rect.shortestSide,
colors, stops, tileMode
);
}
@override
bool operator ==(dynamic other) {
if (identical(this, other))
return true;
if (runtimeType != other.runtimeType)
return false;
final RadialGradient typedOther = other;
if (center != typedOther.center ||
radius != typedOther.radius ||
tileMode != typedOther.tileMode ||
colors?.length != typedOther.colors?.length ||
stops?.length != typedOther.stops?.length)
return false;
if (colors != null) {
assert(typedOther.colors != null);
assert(colors.length == typedOther.colors.length);
for (int i = 0; i < colors.length; i += 1) {
if (colors[i] != typedOther.colors[i])
return false;
}
}
if (stops != null) {
assert(typedOther.stops != null);
assert(stops.length == typedOther.stops.length);
for (int i = 0; i < stops.length; i += 1) {
if (stops[i] != typedOther.stops[i])
return false;
}
}
return true;
}
@override
int get hashCode => hashValues(center, radius, tileMode, hashList(colors), hashList(stops));
@override
String toString() {
return 'RadialGradient($center, $radius, $colors, $stops, $tileMode)';
}
}