feat: Breakpoints utility

lib/utils/breakpoints.dart

@@ -0,0 +1,131 @@
+// Copyright 2013 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 'package:flutter/material.dart';
+
+const Set<TargetPlatform> _desktop = <TargetPlatform>{
+  TargetPlatform.linux,
+  TargetPlatform.macOS,
+  TargetPlatform.windows
+};
+
+const Set<TargetPlatform> _mobile = <TargetPlatform>{
+  TargetPlatform.android,
+  TargetPlatform.fuchsia,
+  TargetPlatform.iOS,
+};
+
+/// A group of standard breakpoints built according to the material
+/// specifications for screen width size.
+///
+/// See also:
+///
+///  * [AdaptiveScaffold], which uses some of these Breakpoints as defaults.
+class Breakpoints {
+  /// This is a standard breakpoint that can be used as a fallthrough in the
+  /// case that no other breakpoint is active.
+  ///
+  /// It is active from a width of -1 dp to infinity.
+  static const Breakpoint standard = WidthPlatformBreakpoint(begin: -1);
+
+  /// A window whose width is less than 600 dp and greater than 0 dp.
+  static const Breakpoint small = WidthPlatformBreakpoint(begin: 0, end: 600);
+
+  /// A window whose width is greater than 0 dp.
+  static const Breakpoint smallAndUp = WidthPlatformBreakpoint(begin: 0);
+
+  /// A desktop screen whose width is less than 600 dp and greater than 0 dp.
+  static const Breakpoint smallDesktop =
+      WidthPlatformBreakpoint(begin: 0, end: 600, platform: _desktop);
+
+  /// A mobile screen whose width is less than 600 dp and greater than 0 dp.
+  static const Breakpoint smallMobile =
+      WidthPlatformBreakpoint(begin: 0, end: 600, platform: _mobile);
+
+  /// A window whose width is between 600 dp and 840 dp.
+  static const Breakpoint medium =
+      WidthPlatformBreakpoint(begin: 600, end: 840);
+
+  /// A window whose width is greater than 600 dp.
+  static const Breakpoint mediumAndUp = WidthPlatformBreakpoint(begin: 600);
+
+  /// A desktop window whose width is between 600 dp and 840 dp.
+  static const Breakpoint mediumDesktop =
+      WidthPlatformBreakpoint(begin: 600, end: 840, platform: _desktop);
+
+  /// A mobile window whose width is between 600 dp and 840 dp.
+  static const Breakpoint mediumMobile =
+      WidthPlatformBreakpoint(begin: 600, end: 840, platform: _mobile);
+
+  /// A window whose width is greater than 840 dp.
+  static const Breakpoint large = WidthPlatformBreakpoint(begin: 840);
+
+  /// A desktop window whose width is greater than 840 dp.
+  static const Breakpoint largeDesktop =
+      WidthPlatformBreakpoint(begin: 840, platform: _desktop);
+
+  /// A mobile window whose width is greater than 840 dp.
+  static const Breakpoint largeMobile =
+      WidthPlatformBreakpoint(begin: 840, platform: _mobile);
+}
+
+/// A class that can be used to quickly generate [Breakpoint]s that depend on
+/// the screen width and the platform.
+class WidthPlatformBreakpoint extends Breakpoint {
+  /// Returns a const [Breakpoint] with the given constraints.
+  const WidthPlatformBreakpoint({this.begin, this.end, this.platform});
+
+  /// The beginning width dp value. If left null then the [Breakpoint] will have
+  /// no lower bound.
+  final double? begin;
+
+  /// The end width dp value. If left null then the [Breakpoint] will have no
+  /// upper bound.
+  final double? end;
+
+  /// A Set of [TargetPlatform]s that the [Breakpoint] will be active on. If
+  /// left null then it will be active on all platforms.
+  final Set<TargetPlatform>? platform;
+
+  @override
+  bool isActive(final BuildContext context) {
+    final TargetPlatform host = Theme.of(context).platform;
+    final bool isRightPlatform = platform?.contains(host) ?? true;
+
+    // Null boundaries are unbounded, assign the max/min of their associated
+    // direction on a number line.
+    final double width = MediaQuery.of(context).size.width;
+    final double lowerBound = begin ?? double.negativeInfinity;
+    final double upperBound = end ?? double.infinity;
+
+    return width >= lowerBound && width < upperBound && isRightPlatform;
+  }
+}
+
+/// An interface to define the conditions that distinguish between types of
+/// screens.
+///
+/// Adaptive apps usually display differently depending on the screen type: a
+/// compact layout for smaller screens, or a relaxed layout for larger screens.
+/// Override this class by defining `isActive` to fetch the screen property
+/// (usually `MediaQuery.of`) and return true if the condition is met.
+///
+/// Breakpoints do not need to be exclusive because they are tested in order
+/// with the last Breakpoint active taking priority.
+///
+/// If the condition is only based on the screen width and/or the device type,
+/// use [WidthPlatformBreakpoint] to define the [Breakpoint].
+///
+/// See also:
+///
+///  * [SlotLayout.config], which uses breakpoints to dictate the layout of the
+///    screen.
+abstract class Breakpoint {
+  /// Returns a const [Breakpoint].
+  const Breakpoint();
+
+  /// A method that returns true based on conditions related to the context of
+  /// the screen such as MediaQuery.of(context).size.width.
+  bool isActive(final BuildContext context);
+}