[Gallery] Fix directory structure (#312)

gallery/lib/layout/adaptive.dart

@@ -0,0 +1,36 @@
+// Copyright 2019 The Flutter team. 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';
+
+enum DisplayType {
+  desktop,
+  mobile,
+}
+
+const _desktopBreakpoint = 700.0;
+const _smallDesktopMaxWidth = 1000.0;
+
+/// Returns the [DisplayType] for the current screen. This app only supports
+/// mobile and desktop layouts, and as such we only have one breakpoint.
+DisplayType displayTypeOf(BuildContext context) {
+  if (MediaQuery.of(context).size.shortestSide > _desktopBreakpoint) {
+    return DisplayType.desktop;
+  } else {
+    return DisplayType.mobile;
+  }
+}
+
+/// Returns a boolean if we are in a display of [DisplayType.desktop]. Used to
+/// build adaptive and responsive layouts.
+bool isDisplayDesktop(BuildContext context) {
+  return displayTypeOf(context) == DisplayType.desktop;
+}
+
+/// Returns a boolean if we are in a display of [DisplayType.desktop] but less
+/// than 1000 width. Used to build adaptive and responsive layouts.
+bool isDisplaySmallDesktop(BuildContext context) {
+  return isDisplayDesktop(context) &&
+      MediaQuery.of(context).size.width < _smallDesktopMaxWidth;
+}

gallery/lib/layout/focus_traversal_policy.dart

@@ -0,0 +1,59 @@
+// Copyright 2019 The Flutter team. 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';
+
+/// [EdgeChildrenFocusTraversalPolicy] can be used to make sure that when you
+/// are at the last or first focus node inside of a focus scope, we'll request
+/// focus for given focus node outside of the scope.
+///
+/// This can be used to for example make sure that you can request focus outside
+/// of the MaterialApp you are currently in.
+class EdgeChildrenFocusTraversalPolicy extends WidgetOrderFocusTraversalPolicy {
+  EdgeChildrenFocusTraversalPolicy({
+    @required this.firstFocusNodeOutsideScope,
+    @required this.lastFocusNodeOutsideScope,
+    this.focusScope,
+    this.firstFocusNodeInsideScope,
+    this.lastFocusNodeInsideScope,
+  }) : assert((focusScope != null &&
+                firstFocusNodeInsideScope == null &&
+                lastFocusNodeInsideScope == null) ||
+            (firstFocusNodeInsideScope != null &&
+                lastFocusNodeInsideScope != null &&
+                focusScope == null));
+
+  final FocusNode firstFocusNodeOutsideScope;
+  final FocusNode lastFocusNodeOutsideScope;
+
+  /// Either provide [focusScope] or both [firstFocusNodeInsideScope]
+  /// and [lastFocusNodeInsideScope].
+  final FocusScopeNode focusScope;
+  final FocusNode firstFocusNodeInsideScope;
+  final FocusNode lastFocusNodeInsideScope;
+
+  @override
+  bool previous(FocusNode currentNode) {
+    if (currentNode ==
+        (firstFocusNodeInsideScope ??
+            focusScope.traversalChildren.toList().first)) {
+      firstFocusNodeOutsideScope.requestFocus();
+      return true;
+    } else {
+      return super.previous(currentNode);
+    }
+  }
+
+  @override
+  bool next(FocusNode currentNode) {
+    if (currentNode ==
+        (lastFocusNodeInsideScope ??
+            focusScope.traversalChildren.toList().last)) {
+      lastFocusNodeOutsideScope.requestFocus();
+      return true;
+    } else {
+      return super.next(currentNode);
+    }
+  }
+}

gallery/lib/layout/highlight_focus.dart

@@ -0,0 +1,96 @@
+// Copyright 2019 The Flutter team. 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';
+import 'package:flutter/services.dart';
+
+/// [HighlightFocus] is a helper widget for giving a child focus
+/// allowing tab-navigation.
+/// Wrap your widget as [child] of a [HighlightFocus] widget.
+class HighlightFocus extends StatefulWidget {
+  const HighlightFocus({
+    @required this.onPressed,
+    @required this.child,
+    this.highlightColor,
+    this.borderColor,
+    this.hasFocus = true,
+    this.debugLabel,
+  });
+
+  /// [onPressed] is called when you press space, enter, or numpad-enter
+  /// when the widget is focused.
+  final VoidCallback onPressed;
+
+  /// [child] is your widget.
+  final Widget child;
+
+  /// [highlightColor] is the color filled in the border when the widget
+  /// is focused.
+  /// Use [Colors.transparent] if you do not want one.
+  /// Use an opacity less than 1 to make the underlying widget visible.
+  final Color highlightColor;
+
+  /// [borderColor] is the color of the border when the widget is focused.
+  final Color borderColor;
+
+  /// [hasFocus] is true when focusing on the widget is allowed.
+  /// Set to false if you want the child to skip focus.
+  final bool hasFocus;
+
+  final String debugLabel;
+
+  @override
+  _HighlightFocusState createState() => _HighlightFocusState();
+}
+
+class _HighlightFocusState extends State<HighlightFocus> {
+  bool isFocused;
+
+  @override
+  void initState() {
+    isFocused = false;
+    super.initState();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    Color _highlightColor = widget.highlightColor ??
+        Theme.of(context).colorScheme.primary.withOpacity(0.5);
+    Color _borderColor =
+        widget.borderColor ?? Theme.of(context).colorScheme.onPrimary;
+
+    BoxDecoration _highlightedDecoration = BoxDecoration(
+      color: _highlightColor,
+      border: Border.all(
+        color: _borderColor,
+        width: 2,
+      ),
+    );
+
+    return Focus(
+      canRequestFocus: widget.hasFocus,
+      debugLabel: widget.debugLabel,
+      onFocusChange: (newValue) {
+        setState(() {
+          isFocused = newValue;
+        });
+      },
+      onKey: (node, event) {
+        if (event is RawKeyDownEvent &&
+            (event.logicalKey == LogicalKeyboardKey.space ||
+                event.logicalKey == LogicalKeyboardKey.enter ||
+                event.logicalKey == LogicalKeyboardKey.numpadEnter)) {
+          widget.onPressed();
+          return true;
+        } else {
+          return false;
+        }
+      },
+      child: Container(
+        foregroundDecoration: isFocused ? _highlightedDecoration : null,
+        child: widget.child,
+      ),
+    );
+  }
+}

gallery/lib/layout/text_scale.dart

@@ -0,0 +1,42 @@
+// Copyright 2019 The Flutter team. 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';
+
+import 'package:flutter/material.dart';
+
+import 'package:gallery/data/gallery_options.dart';
+
+double _textScaleFactor(BuildContext context) {
+  return GalleryOptions.of(context).textScaleFactor(context);
+}
+
+// When text is larger, this factor becomes larger, but at half the rate.
+//
+// | Text scaling | Text scale factor | reducedTextScale(context) |
+// |--------------|-------------------|---------------------------|
+// | Small        |               0.8 |                       1.0 |
+// | Normal       |               1.0 |                       1.0 |
+// | Large        |               2.0 |                       1.5 |
+// | Huge         |               3.0 |                       2.0 |
+
+double reducedTextScale(BuildContext context) {
+  double textScaleFactor = _textScaleFactor(context);
+  return textScaleFactor >= 1 ? (1 + textScaleFactor) / 2 : 1;
+}
+
+// When text is larger, this factor becomes larger at the same rate.
+// But when text is smaller, this factor stays at 1.
+//
+// | Text scaling | Text scale factor |  cappedTextScale(context) |
+// |--------------|-------------------|---------------------------|
+// | Small        |               0.8 |                       1.0 |
+// | Normal       |               1.0 |                       1.0 |
+// | Large        |               2.0 |                       2.0 |
+// | Huge         |               3.0 |                       3.0 |
+
+double cappedTextScale(BuildContext context) {
+  double textScaleFactor = _textScaleFactor(context);
+  return max(textScaleFactor, 1);
+}