Interactive size const (#36964)

(Breaking Change) Move some hardcoded pixel values to reusable constants.

packages/flutter/lib/src/cupertino/button.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
+import 'constants.dart';
 import 'theme.dart';
 
 const Color _kDisabledBackground = Color(0xFFA9A9A9);
@@ -33,7 +34,7 @@ class CupertinoButton extends StatefulWidget {
     this.padding,
     this.color,
     this.disabledColor,
-    this.minSize = 44.0,
+    this.minSize = kMinInteractiveDimensionCupertino,
     this.pressedOpacity = 0.1,
     this.borderRadius = const BorderRadius.all(Radius.circular(8.0)),
     @required this.onPressed,
@@ -52,7 +53,7 @@ class CupertinoButton extends StatefulWidget {
     @required this.child,
     this.padding,
     this.disabledColor,
-    this.minSize = 44.0,
+    this.minSize = kMinInteractiveDimensionCupertino,
     this.pressedOpacity = 0.1,
     this.borderRadius = const BorderRadius.all(Radius.circular(8.0)),
     @required this.onPressed,
@@ -94,12 +95,8 @@ class CupertinoButton extends StatefulWidget {
 
   /// Minimum size of the button.
   ///
-  /// Defaults to 44.0 which the iOS Human Interface Guideline recommends as the
-  /// minimum tappable area
-  ///
-  /// See also:
-  ///
-  ///  * <https://developer.apple.com/ios/human-interface-guidelines/visual-design/adaptivity-and-layout/>
+  /// Defaults to kMinInteractiveDimensionCupertino which the iOS Human
+  /// Interface Guidelines recommends as the minimum tappable area.
   final double minSize;
 
   /// The opacity that the button will fade to when it is pressed.

packages/flutter/lib/src/cupertino/constants.dart

+// Copyright 2019 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.
+
+/// The minimum dimension of any interactive region according to the iOS Human
+/// Interface Guidelines.
+///
+/// This is used to avoid small regions that are hard for the user to interact
+/// with. It applies to both dimensions of a region, so a square of size
+/// kMinInteractiveDimension x kMinInteractiveDimension is the smallest
+/// acceptable region that should respond to gestures.
+///
+/// See also:
+///
+///  * [kMinInteractiveDimension]
+///  * <https://developer.apple.com/ios/human-interface-guidelines/visual-design/adaptivity-and-layout/>
+const double kMinInteractiveDimensionCupertino = 44.0;

packages/flutter/lib/src/cupertino/nav_bar.dart

@@ -11,6 +11,7 @@ import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
 import 'button.dart';
+import 'constants.dart';
 import 'icons.dart';
 import 'page_scaffold.dart';
 import 'route.dart';
@@ -19,7 +20,7 @@ import 'theme.dart';
 /// Standard iOS navigation bar height without the status bar.
 ///
 /// This height is constant and independent of accessibility as it is in iOS.
-const double _kNavBarPersistentHeight = 44.0;
+const double _kNavBarPersistentHeight = kMinInteractiveDimensionCupertino;
 
 /// Size increase from expanding the navigation bar into an iOS-11-style large title
 /// form in a [CustomScrollView].

packages/flutter/lib/src/material/chip.dart

@@ -11,6 +11,7 @@ import 'package:flutter/widgets.dart';
 
 import 'chip_theme.dart';
 import 'colors.dart';
+import 'constants.dart';
 import 'debug.dart';
 import 'icons.dart';
 import 'ink_well.dart';
@@ -1731,7 +1732,7 @@ class _RawChipState extends State<RawChip> with TickerProviderStateMixin<RawChip
     BoxConstraints constraints;
     switch (widget.materialTapTargetSize ?? theme.materialTapTargetSize) {
       case MaterialTapTargetSize.padded:
-        constraints = const BoxConstraints(minHeight: 48.0);
+        constraints = const BoxConstraints(minHeight: kMinInteractiveDimension);
         break;
       case MaterialTapTargetSize.shrinkWrap:
         constraints = const BoxConstraints();

packages/flutter/lib/src/material/constants.dart

@@ -4,6 +4,20 @@
 
 import 'package:flutter/painting.dart';
 
+/// The minimum dimension of any interactive region according to Material
+/// guidelines.
+///
+/// This is used to avoid small regions that are hard for the user to interact
+/// with. It applies to both dimensions of a region, so a square of size
+/// kMinInteractiveDimension x kMinInteractiveDimension is the smallest
+/// acceptable region that should respond to gestures.
+///
+/// See also:
+///
+///  * [kMinInteractiveDimensionCupertino]
+///  * The Material spec on touch targets at <https://material.io/design/usability/accessibility.html#layout-typography>.
+const double kMinInteractiveDimension = 48.0;
+
 /// The height of the toolbar component of the [AppBar].
 const double kToolbarHeight = 56.0;
 
@@ -11,7 +25,7 @@ const double kToolbarHeight = 56.0;
 const double kBottomNavigationBarHeight = 56.0;
 
 /// The height of a tab bar containing text.
-const double kTextTabBarHeight = 48.0;
+const double kTextTabBarHeight = kMinInteractiveDimension;
 
 /// The amount of time theme change animations should last.
 const Duration kThemeChangeDuration = Duration(milliseconds: 200);

packages/flutter/lib/src/material/data_table.dart

@@ -10,6 +10,7 @@ import 'package:flutter/widgets.dart';
 
 import 'checkbox.dart';
 import 'colors.dart';
+import 'constants.dart';
 import 'debug.dart';
 import 'divider.dart';
 import 'dropdown.dart';
@@ -262,7 +263,7 @@ class DataTable extends StatelessWidget {
     this.sortColumnIndex,
     this.sortAscending = true,
     this.onSelectAll,
-    this.dataRowHeight = 48.0,
+    this.dataRowHeight = kMinInteractiveDimension,
     this.headingRowHeight = 56.0,
     this.horizontalMargin = 24.0,
     this.columnSpacing = 56.0,
@@ -321,7 +322,8 @@ class DataTable extends StatelessWidget {
 
   /// The height of each row (excluding the row that contains column headings).
   ///
-  /// This value defaults to 48.0 to adhere to the Material Design specifications.
+  /// This value defaults to kMinInteractiveDimension to adhere to the Material
+  /// Design specifications.
   final double dataRowHeight;
 
   /// The height of the heading row.

packages/flutter/lib/src/material/dropdown.dart

@@ -20,7 +20,7 @@ import 'shadows.dart';
 import 'theme.dart';
 
 const Duration _kDropdownMenuDuration = Duration(milliseconds: 300);
-const double _kMenuItemHeight = 48.0;
+const double _kMenuItemHeight = kMinInteractiveDimension;
 const double _kDenseButtonHeight = 24.0;
 const EdgeInsets _kMenuItemPadding = EdgeInsets.symmetric(horizontal: 16.0);
 const EdgeInsetsGeometry _kAlignedButtonPadding = EdgeInsetsDirectional.only(start: 16.0, end: 4.0);

packages/flutter/lib/src/material/expansion_panel.dart

@@ -5,13 +5,14 @@
 import 'package:flutter/rendering.dart';
 import 'package:flutter/widgets.dart';
 
+import 'constants.dart';
 import 'expand_icon.dart';
 import 'ink_well.dart';
 import 'material_localizations.dart';
 import 'mergeable_material.dart';
 import 'theme.dart';
 
-const double _kPanelHeaderCollapsedHeight = 48.0;
+const double _kPanelHeaderCollapsedHeight = kMinInteractiveDimension;
 const double _kPanelHeaderExpandedHeight = 64.0;
 
 class _SaltedKey<S, V> extends LocalKey {

packages/flutter/lib/src/material/icon_button.dart

@@ -7,6 +7,7 @@ import 'dart:math' as math;
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';
 
+import 'constants.dart';
 import 'debug.dart';
 import 'icons.dart';
 import 'ink_well.dart';
@@ -15,8 +16,8 @@ import 'theme.dart';
 import 'tooltip.dart';
 
 // Minimum logical pixel size of the IconButton.
-// See: <https://material.io/guidelines/layout/metrics-keylines.html#metrics-keylines-touch-target-size>
-const double _kMinButtonSize = 48.0;
+// See: <https://material.io/design/usability/accessibility.html#layout-typography>.
+const double _kMinButtonSize = kMinInteractiveDimension;
 
 /// A material design icon button.
 ///
@@ -31,9 +32,9 @@ const double _kMinButtonSize = 48.0;
 ///
 /// Requires one of its ancestors to be a [Material] widget.
 ///
-/// The hit region of an icon button will, if possible, be at least 48.0 pixels
-/// in size, regardless of the actual [iconSize], to satisfy the [touch target
-/// size](https://material.io/guidelines/layout/metrics-keylines.html#metrics-keylines-touch-target-size)
+/// The hit region of an icon button will, if possible, be at least
+/// kMinInteractiveDimension pixels in size, regardless of the actual
+/// [iconSize], to satisfy the [touch target size](https://material.io/guidelines/layout/metrics-keylines.html#metrics-keylines-touch-target-size)
 /// requirements in the Material Design specification. The [alignment] controls
 /// how the icon itself is positioned within the hit region.
 ///

packages/flutter/lib/src/material/paginated_data_table.dart

@@ -11,6 +11,7 @@ import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'button_bar.dart';
 import 'button_theme.dart';
 import 'card.dart';
+import 'constants.dart';
 import 'data_table.dart';
 import 'data_table_source.dart';
 import 'debug.dart';
@@ -70,7 +71,7 @@ class PaginatedDataTable extends StatefulWidget {
     this.sortColumnIndex,
     this.sortAscending = true,
     this.onSelectAll,
-    this.dataRowHeight = 48.0,
+    this.dataRowHeight = kMinInteractiveDimension,
     this.headingRowHeight = 56.0,
     this.horizontalMargin = 24.0,
     this.columnSpacing = 56.0,
@@ -141,7 +142,8 @@ class PaginatedDataTable extends StatefulWidget {
 
   /// The height of each row (excluding the row that contains column headings).
   ///
-  /// This value is optional and defaults to 48.0 if not specified.
+  /// This value is optional and defaults to kMinInteractiveDimension if not
+  /// specified.
   final double dataRowHeight;
 
   /// The height of the heading row.

packages/flutter/lib/src/material/popup_menu.dart

@@ -30,7 +30,7 @@ const Duration _kMenuDuration = Duration(milliseconds: 300);
 const double _kBaselineOffsetFromBottom = 20.0;
 const double _kMenuCloseIntervalEnd = 2.0 / 3.0;
 const double _kMenuHorizontalPadding = 16.0;
-const double _kMenuItemHeight = 48.0;
+const double _kMenuItemHeight = kMinInteractiveDimension;
 const double _kMenuDividerHeight = 16.0;
 const double _kMenuMaxWidth = 5.0 * _kMenuWidthStep;
 const double _kMenuMinWidth = 2.0 * _kMenuWidthStep;
@@ -132,8 +132,8 @@ class _PopupMenuDividerState extends State<PopupMenuDivider> {
 ///
 /// Typically the [child] of a [PopupMenuItem] is a [Text] widget. More
 /// elaborate menus with icons can use a [ListTile]. By default, a
-/// [PopupMenuItem] is 48 pixels high. If you use a widget with a different
-/// height, it must be specified in the [height] property.
+/// [PopupMenuItem] is kMinInteractiveDimension pixels high. If you use a widget
+/// with a different height, it must be specified in the [height] property.
 ///
 /// {@tool sample}
 ///
@@ -189,7 +189,7 @@ class PopupMenuItem<T> extends PopupMenuEntry<T> {
 
   /// The height of the entry.
   ///
-  /// Defaults to 48 pixels.
+  /// Defaults to kMinInteractiveDimension pixels.
   @override
   final double height;
 
@@ -292,9 +292,10 @@ class PopupMenuItemState<T, W extends PopupMenuItem<T>> extends State<W> {
 /// To show a popup menu, use the [showMenu] function. To create a button that
 /// shows a popup menu, consider using [PopupMenuButton].
 ///
-/// A [CheckedPopupMenuItem] is 48 pixels high, which matches the default height
-/// of a [PopupMenuItem]. The horizontal layout uses a [ListTile]; the checkmark
-/// is an [Icons.done] icon, shown in the [ListTile.leading] position.
+/// A [CheckedPopupMenuItem] is kMinInteractiveDimension pixels high, which
+/// matches the default height of a [PopupMenuItem]. The horizontal layout uses
+/// a [ListTile]; the checkmark is an [Icons.done] icon, shown in the
+/// [ListTile.leading] position.
 ///
 /// {@tool sample}
 ///

packages/flutter/lib/src/material/range_slider.dart

@@ -333,7 +333,7 @@ class RangeSlider extends StatefulWidget {
   final RangeSemanticFormatterCallback semanticFormatterCallback;
 
   // Touch width for the tap boundary of the slider thumbs.
-  static const double _minTouchTargetWidth = 48;
+  static const double _minTouchTargetWidth = kMinInteractiveDimension;
 
   @override
   _RangeSliderState createState() => _RangeSliderState();

packages/flutter/lib/src/widgets/constants.dart

+// Copyright 2019 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.
+
+/// The minimum dimension of any interactive region according to the Material
+/// guidelines.
+///
+/// This is used to avoid small regions that are hard for the user to interact
+/// with. It applies to both dimensions of a region, so a square of size
+/// kMinInteractiveDimension x kMinInteractiveDimension is the smallest
+/// acceptable region that should respond to gestures.
+///
+/// See also:
+///
+///  * [kMinInteractiveDimensionCupertino]
+const double kMinInteractiveDimension = 48.0;

packages/flutter/lib/src/widgets/editable_text.dart

@@ -16,6 +16,7 @@ import 'package:flutter/gestures.dart' show DragStartBehavior;
 import 'automatic_keep_alive.dart';
 import 'basic.dart';
 import 'binding.dart';
+import 'constants.dart';
 import 'debug.dart';
 import 'focus_manager.dart';
 import 'focus_scope.dart';
@@ -1446,7 +1447,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
           .getHandleSize(renderEditable.preferredLineHeight).height;
         final double interactiveHandleHeight = math.max(
           handleHeight,
-          kMinInteractiveSize,
+          kMinInteractiveDimension,
         );
         final Offset anchor = _selectionOverlay.selectionControls
           .getHandleAnchor(

packages/flutter/lib/src/widgets/text_selection.dart

@@ -12,6 +12,7 @@ import 'package:flutter/scheduler.dart';
 import 'package:flutter/services.dart';
 
 import 'basic.dart';
+import 'constants.dart';
 import 'container.dart';
 import 'editable_text.dart';
 import 'framework.dart';
@@ -618,11 +619,6 @@ class _TextSelectionHandleOverlay extends StatefulWidget {
   }
 }
 
-/// The minimum size that a widget should be in order to be easily interacted
-/// with by the user.
-@visibleForTesting
-const double kMinInteractiveSize = 48.0;
-
 class _TextSelectionHandleOverlayState
     extends State<_TextSelectionHandleOverlay> with SingleTickerProviderStateMixin {
   Offset _dragPosition;
@@ -749,7 +745,7 @@ class _TextSelectionHandleOverlayState
 
     // Make sure the GestureDetector is big enough to be easily interactive.
     final Rect interactiveRect = handleRect.expandToInclude(
-      Rect.fromCircle(center: handleRect.center, radius: kMinInteractiveSize / 2),
+      Rect.fromCircle(center: handleRect.center, radius: kMinInteractiveDimension/ 2),
     );
     final RelativeRect padding = RelativeRect.fromLTRB(
       math.max((interactiveRect.width - handleRect.width) / 2, 0),

packages/flutter/test/widgets/editable_text_test.dart

@@ -2268,8 +2268,8 @@ void main() {
             expect(
               pos,
               inExclusiveRange(
-                0 - kMinInteractiveSize,
-                0 + kMinInteractiveSize,
+                0 - kMinInteractiveDimension,
+                0 + kMinInteractiveDimension,
               ),
             );
             break;
@@ -2277,8 +2277,8 @@ void main() {
             expect(
               pos,
               inExclusiveRange(
-                viewport.width - kMinInteractiveSize,
-                viewport.width + kMinInteractiveSize,
+                viewport.width - kMinInteractiveDimension,
+                viewport.width + kMinInteractiveDimension,
               ),
             );
             break;
@@ -2286,8 +2286,8 @@ void main() {
             expect(
               pos,
               inExclusiveRange(
-                0 - kMinInteractiveSize,
-                viewport.width + kMinInteractiveSize,
+                0 - kMinInteractiveDimension,
+                viewport.width + kMinInteractiveDimension,
               ),
             );
             break;
@@ -2381,15 +2381,15 @@ void main() {
     expect(
       handles[0].localToGlobal(Offset.zero).dx,
       inExclusiveRange(
-        -kMinInteractiveSize,
-        kMinInteractiveSize,
+        -kMinInteractiveDimension,
+        kMinInteractiveDimension,
       ),
     );
     expect(
       handles[1].localToGlobal(Offset.zero).dx,
       inExclusiveRange(
-        70.0 - kMinInteractiveSize,
-        70.0 + kMinInteractiveSize,
+        70.0 - kMinInteractiveDimension,
+        70.0 + kMinInteractiveDimension,
       ),
     );
     expect(state.selectionOverlay.handlesAreVisible, isTrue);
@@ -2497,8 +2497,8 @@ void main() {
             expect(
               pos,
               inExclusiveRange(
-                0 - kMinInteractiveSize,
-                0 + kMinInteractiveSize,
+                0 - kMinInteractiveDimension,
+                0 + kMinInteractiveDimension,
               ),
             );
             break;
@@ -2506,8 +2506,8 @@ void main() {
             expect(
               pos,
               inExclusiveRange(
-                viewport.width - kMinInteractiveSize,
-                viewport.width + kMinInteractiveSize,
+                viewport.width - kMinInteractiveDimension,
+                viewport.width + kMinInteractiveDimension,
               ),
             );
             break;
@@ -2515,8 +2515,8 @@ void main() {
             expect(
               pos,
               inExclusiveRange(
-                0 - kMinInteractiveSize,
-                viewport.width + kMinInteractiveSize,
+                0 - kMinInteractiveDimension,
+                viewport.width + kMinInteractiveDimension,
               ),
             );
             break;