outlined_button.dart

// Copyright 2014 The Flutter 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:math' as math;
import 'dart:ui' show lerpDouble;

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

import 'button_style.dart';
import 'button_style_button.dart';
import 'color_scheme.dart';
import 'colors.dart';
import 'constants.dart';
import 'ink_ripple.dart';
import 'ink_well.dart';
import 'material_state.dart';
import 'outlined_button_theme.dart';
import 'theme.dart';
import 'theme_data.dart';

/// A Material Design "Outlined Button"; essentially a [TextButton]
/// with an outlined border.
///
/// Outlined buttons are medium-emphasis buttons. They contain actions
/// that are important, but they aren’t the primary action in an app.
///
/// An outlined button is a label [child] displayed on a (zero
/// elevation) [Material] widget. The label's [Text] and [Icon]
/// widgets are displayed in the [style]'s
/// [ButtonStyle.foregroundColor] and the outline's weight and color
/// are defined by [ButtonStyle.side].  The button reacts to touches
/// by filling with the [style]'s [ButtonStyle.backgroundColor].
///
/// The outlined button's default style is defined by [defaultStyleOf].
/// The style of this outline button can be overridden with its [style]
/// parameter. The style of all text buttons in a subtree can be
/// overridden with the [OutlinedButtonTheme] and the style of all of the
/// outlined buttons in an app can be overridden with the [Theme]'s
/// [ThemeData.outlinedButtonTheme] property.
///
/// Unlike [TextButton] or [ElevatedButton], outline buttons have a
/// default [ButtonStyle.side] which defines the appearance of the
/// outline.  Because the default `side` is non-null, it
/// unconditionally overrides the shape's [OutlinedBorder.side]. In
/// other words, to specify an outlined button's shape _and_ the
/// appearance of its outline, both the [ButtonStyle.shape] and
/// [ButtonStyle.side] properties must be specified.
///
/// {@tool dartpad --template=stateless_widget_scaffold_center}
/// Here is an example of a basic [OutlinedButton].
///
/// ** See code in examples/api/lib/material/outlined_button/outlined_button.0.dart **
/// {@end-tool}
///
/// The static [styleFrom] method is a convenient way to create a
/// outlined button [ButtonStyle] from simple values.
///
/// See also:
///
///  * [ElevatedButton], a filled material design button with a shadow.
///  * [TextButton], a material design button without a shadow.
///  * <https://material.io/design/components/buttons.html>
class OutlinedButton extends ButtonStyleButton {
  /// Create an OutlinedButton.
  ///
  /// The [autofocus] and [clipBehavior] arguments must not be null.
  const OutlinedButton({
    Key? key,
    required VoidCallback? onPressed,
    VoidCallback? onLongPress,
    ButtonStyle? style,
    FocusNode? focusNode,
    bool autofocus = false,
    Clip clipBehavior = Clip.none,
    required Widget child,
  }) : super(
    key: key,
    onPressed: onPressed,
    onLongPress: onLongPress,
    style: style,
    focusNode: focusNode,
    autofocus: autofocus,
    clipBehavior: clipBehavior,
    child: child,
  );

  /// Create a text button from a pair of widgets that serve as the button's
  /// [icon] and [label].
  ///
  /// The icon and label are arranged in a row and padded by 12 logical pixels
  /// at the start, and 16 at the end, with an 8 pixel gap in between.
  ///
  /// The [icon] and [label] arguments must not be null.
  factory OutlinedButton.icon({
    Key? key,
    required VoidCallback? onPressed,
    VoidCallback? onLongPress,
    ButtonStyle? style,
    FocusNode? focusNode,
    bool? autofocus,
    Clip? clipBehavior,
    required Widget icon,
    required Widget label,
  }) = _OutlinedButtonWithIcon;

  /// A static convenience method that constructs an outlined button
  /// [ButtonStyle] given simple values.
  ///
  /// The [primary], and [onSurface] colors are used to create a
  /// [MaterialStateProperty] [ButtonStyle.foregroundColor] value in the same
  /// way that [defaultStyleOf] uses the [ColorScheme] colors with the same
  /// names. Specify a value for [primary] to specify the color of the button's
  /// text and icons as well as the overlay colors used to indicate the hover,
  /// focus, and pressed states. Use [onSurface] to specify the button's
  /// disabled text and icon color.
  ///
  /// Similarly, the [enabledMouseCursor] and [disabledMouseCursor]
  /// parameters are used to construct [ButtonStyle.mouseCursor].
  ///
  /// All of the other parameters are either used directly or used to
  /// create a [MaterialStateProperty] with a single value for all
  /// states.
  ///
  /// All parameters default to null, by default this method returns
  /// a [ButtonStyle] that doesn't override anything.
  ///
  /// For example, to override the default shape and outline for an
  /// [OutlinedButton], one could write:
  ///
  /// ```dart
  /// OutlinedButton(
  ///   style: OutlinedButton.styleFrom(
  ///      shape: StadiumBorder(),
  ///      side: BorderSide(width: 2, color: Colors.green),
  ///   ),
  /// )
  /// ```
  static ButtonStyle styleFrom({
    Color? primary,
    Color? onSurface,
    Color? backgroundColor,
    Color? shadowColor,
    double? elevation,
    TextStyle? textStyle,
    EdgeInsetsGeometry? padding,
    Size? minimumSize,
    Size? fixedSize,
    Size? maximumSize,
    BorderSide? side,
    OutlinedBorder? shape,
    MouseCursor? enabledMouseCursor,
    MouseCursor? disabledMouseCursor,
    VisualDensity? visualDensity,
    MaterialTapTargetSize? tapTargetSize,
    Duration? animationDuration,
    bool? enableFeedback,
    AlignmentGeometry? alignment,
    InteractiveInkFeatureFactory? splashFactory,
  }) {
    final MaterialStateProperty<Color?>? foregroundColor = (onSurface == null && primary == null)
      ? null
      : _OutlinedButtonDefaultForeground(primary, onSurface);
    final MaterialStateProperty<Color?>? overlayColor = (primary == null)
      ? null
      : _OutlinedButtonDefaultOverlay(primary);
    final MaterialStateProperty<MouseCursor>? mouseCursor = (enabledMouseCursor == null && disabledMouseCursor == null)
      ? null
      : _OutlinedButtonDefaultMouseCursor(enabledMouseCursor!, disabledMouseCursor!);

    return ButtonStyle(
      textStyle: ButtonStyleButton.allOrNull<TextStyle>(textStyle),
      foregroundColor: foregroundColor,
      backgroundColor: ButtonStyleButton.allOrNull<Color>(backgroundColor),
      overlayColor: overlayColor,
      shadowColor: ButtonStyleButton.allOrNull<Color>(shadowColor),
      elevation: ButtonStyleButton.allOrNull<double>(elevation),
      padding: ButtonStyleButton.allOrNull<EdgeInsetsGeometry>(padding),
      minimumSize: ButtonStyleButton.allOrNull<Size>(minimumSize),
      fixedSize: ButtonStyleButton.allOrNull<Size>(fixedSize),
      maximumSize: ButtonStyleButton.allOrNull<Size>(maximumSize),
      side: ButtonStyleButton.allOrNull<BorderSide>(side),
      shape: ButtonStyleButton.allOrNull<OutlinedBorder>(shape),
      mouseCursor: mouseCursor,
      visualDensity: visualDensity,
      tapTargetSize: tapTargetSize,
      animationDuration: animationDuration,
      enableFeedback: enableFeedback,
      alignment: alignment,
      splashFactory: splashFactory,
    );
  }

  /// Defines the button's default appearance.
  ///
  /// With the exception of [ButtonStyle.side], which defines the
  /// outline, and [ButtonStyle.padding], the returned style is the
  /// same as for [TextButton].
  ///
  /// The button [child]'s [Text] and [Icon] widgets are rendered with
  /// the [ButtonStyle]'s foreground color. The button's [InkWell] adds
  /// the style's overlay color when the button is focused, hovered
  /// or pressed. The button's background color becomes its [Material]
  /// color and is transparent by default.
  ///
  /// All of the ButtonStyle's defaults appear below. In this list
  /// "Theme.foo" is shorthand for `Theme.of(context).foo`. Color
  /// scheme values like "onSurface(0.38)" are shorthand for
  /// `onSurface.withOpacity(0.38)`. [MaterialStateProperty] valued
  /// properties that are not followed by a sublist have the same
  /// value for all states, otherwise the values are as specified for
  /// each state and "others" means all other states.
  ///
  /// The color of the [ButtonStyle.textStyle] is not used, the
  /// [ButtonStyle.foregroundColor] is used instead.
  ///
  /// * `textStyle` - Theme.textTheme.button
  /// * `backgroundColor` - transparent
  /// * `foregroundColor`
  ///   * disabled - Theme.colorScheme.onSurface(0.38)
  ///   * others - Theme.colorScheme.primary
  /// * `overlayColor`
  ///   * hovered - Theme.colorScheme.primary(0.04)
  ///   * focused or pressed - Theme.colorScheme.primary(0.12)
  /// * `shadowColor` - Theme.shadowColor
  /// * `elevation` - 0
  /// * `padding`
  ///   * `textScaleFactor <= 1` - horizontal(16)
  ///   * `1 < textScaleFactor <= 2` - lerp(horizontal(16), horizontal(8))
  ///   * `2 < textScaleFactor <= 3` - lerp(horizontal(8), horizontal(4))
  ///   * `3 < textScaleFactor` - horizontal(4)
  /// * `minimumSize` - Size(64, 36)
  /// * `fixedSize` - null
  /// * `maximumSize` - Size.infinite
  /// * `side` - BorderSide(width: 1, color: Theme.colorScheme.onSurface(0.12))
  /// * `shape` - RoundedRectangleBorder(borderRadius: BorderRadius.circular(4))
  /// * `mouseCursor`
  ///   * disabled - SystemMouseCursors.forbidden
  ///   * others - SystemMouseCursors.click
  /// * `visualDensity` - theme.visualDensity
  /// * `tapTargetSize` - theme.materialTapTargetSize
  /// * `animationDuration` - kThemeChangeDuration
  /// * `enableFeedback` - true
  /// * `alignment` - Alignment.center
  /// * `splashFactory` - InkRipple.splashFactory
  @override
  ButtonStyle defaultStyleOf(BuildContext context) {
    final ThemeData theme = Theme.of(context);
    final ColorScheme colorScheme = theme.colorScheme;

    final EdgeInsetsGeometry scaledPadding = ButtonStyleButton.scaledPadding(
      const EdgeInsets.symmetric(horizontal: 16),
      const EdgeInsets.symmetric(horizontal: 8),
      const EdgeInsets.symmetric(horizontal: 4),
      MediaQuery.maybeOf(context)?.textScaleFactor ?? 1,
    );

    return styleFrom(
      primary: colorScheme.primary,
      onSurface: colorScheme.onSurface,
      backgroundColor: Colors.transparent,
      shadowColor: theme.shadowColor,
      elevation: 0,
      textStyle: theme.textTheme.button,
      padding: scaledPadding,
      minimumSize: const Size(64, 36),
      maximumSize: Size.infinite,
      side: BorderSide(
        color: Theme.of(context).colorScheme.onSurface.withOpacity(0.12),
        width: 1,
      ),
      shape: const RoundedRectangleBorder(borderRadius: BorderRadius.all(Radius.circular(4))),
      enabledMouseCursor: SystemMouseCursors.click,
      disabledMouseCursor: SystemMouseCursors.forbidden,
      visualDensity: theme.visualDensity,
      tapTargetSize: theme.materialTapTargetSize,
      animationDuration: kThemeChangeDuration,
      enableFeedback: true,
      alignment: Alignment.center,
      splashFactory: InkRipple.splashFactory,
    );
  }

  @override
  ButtonStyle? themeStyleOf(BuildContext context) {
    return OutlinedButtonTheme.of(context).style;
  }
}

@immutable
class _OutlinedButtonDefaultForeground extends MaterialStateProperty<Color?>  with Diagnosticable {
  _OutlinedButtonDefaultForeground(this.primary, this.onSurface);

  final Color? primary;
  final Color? onSurface;

  @override
  Color? resolve(Set<MaterialState> states) {
    if (states.contains(MaterialState.disabled))
      return onSurface?.withOpacity(0.38);
    return primary;
  }
}

@immutable
class _OutlinedButtonDefaultOverlay extends MaterialStateProperty<Color?> with Diagnosticable {
  _OutlinedButtonDefaultOverlay(this.primary);

  final Color primary;

  @override
  Color? resolve(Set<MaterialState> states) {
    if (states.contains(MaterialState.hovered))
      return primary.withOpacity(0.04);
    if (states.contains(MaterialState.focused) || states.contains(MaterialState.pressed))
      return primary.withOpacity(0.12);
    return null;
  }
}

@immutable
class _OutlinedButtonDefaultMouseCursor extends MaterialStateProperty<MouseCursor> with Diagnosticable {
  _OutlinedButtonDefaultMouseCursor(this.enabledCursor, this.disabledCursor);

  final MouseCursor enabledCursor;
  final MouseCursor disabledCursor;

  @override
  MouseCursor resolve(Set<MaterialState> states) {
    if (states.contains(MaterialState.disabled))
      return disabledCursor;
    return enabledCursor;
  }
}

class _OutlinedButtonWithIcon extends OutlinedButton {
  _OutlinedButtonWithIcon({
    Key? key,
    required VoidCallback? onPressed,
    VoidCallback? onLongPress,
    ButtonStyle? style,
    FocusNode? focusNode,
    bool? autofocus,
    Clip? clipBehavior,
    required Widget icon,
    required Widget label,
  }) : assert(icon != null),
       assert(label != null),
       super(
         key: key,
         onPressed: onPressed,
         onLongPress: onLongPress,
         style: style,
         focusNode: focusNode,
         autofocus: autofocus ?? false,
         clipBehavior: clipBehavior ?? Clip.none,
         child: _OutlinedButtonWithIconChild(icon: icon, label: label),
      );
}

class _OutlinedButtonWithIconChild extends StatelessWidget {
  const _OutlinedButtonWithIconChild({
    Key? key,
    required this.label,
    required this.icon,
  }) : super(key: key);

  final Widget label;
  final Widget icon;

  @override
  Widget build(BuildContext context) {
    final double scale = MediaQuery.maybeOf(context)?.textScaleFactor ?? 1;
    final double gap = scale <= 1 ? 8 : lerpDouble(8, 4, math.min(scale - 1, 1))!;
    return Row(
      mainAxisSize: MainAxisSize.min,
      children: <Widget>[icon, SizedBox(width: gap), Flexible(child: label)],
    );
  }
}