This pull request aims to improve code readability, based on feedback gathered in a recent design doc.
<br>
There are two factors that hugely impact how easy it is to understand a piece of code: **verbosity** and **complexity**.
Reducing **verbosity** is important, because boilerplate makes a project more difficult to navigate. It also has a tendency to make one's eyes gloss over, and subtle typos/bugs become more likely to slip through.
Reducing **complexity** makes the code more accessible to more people. This is especially important for open-source projects like Flutter, where the code is read by those who make contributions, as well as others who read through source code as they debug their own projects.
<hr>
<br>
The following examples show how pattern-matching might affect these two factors:
<details> <summary><h3>Example 1 (GOOD)</h3> [click to expand]</summary>
```dart
if (ancestor case InheritedElement(:final InheritedTheme widget)) {
themes.add(widget);
}
```
Without using patterns, this might expand to
```dart
if (ancestor is InheritedElement) {
final InheritedWidget widget = ancestor.widget;
if (widget is InheritedTheme) {
themes.add(widget);
}
}
```
Had `ancestor` been a non-local variable, it would need to be "converted" as well:
```dart
final Element ancestor = this.ancestor;
if (ancestor is InheritedElement) {
final InheritedWidget inheritedWidget = ancestor.widget;
if (widget is InheritedTheme) {
themes.add(theme);
}
}
```
</details>
<details> <summary><h3>Example 2 (BAD) </h3> [click to expand]</summary>
```dart
if (widget case PreferredSizeWidget(preferredSize: Size(:final double height))) {
return height;
}
```
Assuming `widget` is a non-local variable, this would expand to:
```dart
final Widget widget = this.widget;
if (widget is PreferredSizeWidget) {
return widget.preferredSize.height;
}
```
<br>
</details>
In both of the examples above, an `if-case` statement simultaneously verifies that an object meets the specified criteria and performs a variable assignment accordingly.
But there are some differences: Example 2 uses a more deeply-nested pattern than Example 1 but makes fewer useful checks.
**Example 1:**
- checks that `ancestor` is an `InheritedElement`
- checks that the inherited element's `widget` is an `InheritedTheme`
**Example 2:**
- checks that `widget` is a `PreferredSizeWidget`
(every `PreferredSizeWidget` has a `size` field, and every `Size` has a `height` field)
<br>
<hr>
I feel hesitant to try presenting a set of cut-and-dry rules as to which scenarios should/shouldn't use pattern-matching, since there are an abundance of different types of patterns, and an abundance of different places where they might be used.
But hopefully the conversations we've had recently will help us converge toward a common intuition of how pattern-matching can best be utilized for improved readability.
<br><br>
- resolves https://github.com/flutter/flutter/issues/152313
- Design Doc: [flutter.dev/go/dart-patterns](https://flutter.dev/go/dart-patterns)
Fixes#33799
Allows for a route to inform the route below it in the navigation stack how to animate when the topmost route enters are leaves the stack.
It does this by making a `DelegatedTransition` available for the previous route to look up and use. If available, the route lower in the stack will wrap it's transition builders with that delegated transition and use it instead of it's default secondary transition.
This is what the sample code in this PR shows an app that is able to use both a Material zoom transition and a Cupertino slide transition in one app. It also includes a custom vertical transition. Every page animates off the screen in a way to match up with the incoming page's transition. When popped, the correct transitions play in reverse.
https://github.com/user-attachments/assets/1fc910fa-8cde-4e05-898e-daad8ff4a697
The below video shows this logic making a pseudo iOS styled sheet transition.
https://github.com/flutter/flutter/assets/58190796/207163d8-d87f-48b1-aad9-7e770d1d96c5
All existing page transitions in Flutter will be overwritten by the incoming route if a `delegatedTransition` is provided. This can be opted out of through `canTransitionTo` for a new route widget. Of Flutter's existing page transitions, this PR only adds a `DelegatedTransition` for the Zoom and Cupertino transitions. The other transitions possible in Material will get delegated transitions in a later PR.
Fixes https://github.com/flutter/flutter/issues/155551
### Description
- Adds example for `WidgetStateMouseCursor`
- Adds tests for `examples/api/lib/widgets/widget_state/widget_state_mouse_cursor.0.dart`
Fixes https://github.com/flutter/flutter/issues/155557
### Description
- Adds example for `WidgetStateBorderSide`
- Adds tests for `examples/api/lib/widgets/widget_state/widget_state_border_side.0.dart`
This PR contributes to https://github.com/flutter/flutter/issues/155313
### Description
- Adds example for `WidgetStateProperty`
- Adds tests for `examples/api/lib/widgets/widget_state/widget_state_property.0.dart`
I've updated these two examples to support state restoration of the navigation stack and verified that they work with predictive back in the tests. This was motivated by a worry that users are not properly setting up their navigation and that our examples are misleading them in the name of simplicity.
Currently, there are 21 `.resolveWith()` calls in example files.
This pull request changes 11 of them to use the new `.fromMap()` constructor. (Seven of them are now `const`!)
```dart
ListTile(
iconColor: WidgetStateColor.fromMap(<WidgetStatesConstraint, Color>{
WidgetState.disabled: Colors.red,
WidgetState.selected: Colors.green,
WidgetState.any: Colors.black,
}),
// The same can be achieved using the .resolveWith() constructor.
// The text color will be identical to the icon color above.
textColor: WidgetStateColor.resolveWith((Set<WidgetState> states) {
if (states.contains(WidgetState.disabled)) {
return Colors.red;
}
if (states.contains(WidgetState.selected)) {
return Colors.green;
}
return Colors.black;
}),
),
```
This PR contains:
- 3 instances of `colorScheme.background` â `colorScheme.surface`
- and a whole bunch of `MaterialState` â `WidgetState`
As of yet, no changes have been made to example test files or the [examples/api/lib/material/material_state/](0b2a8e589e/examples/api/lib/material/material_state) directory.
(related: #151373)
A relatively elaborate PinnedSliverHeader example which creates an app bar that's similar to the one that appears in the iOS Settings app. In this example the pinned header starts out transparent and the first item in the list serves as the app's "Settings" title. When the title item has been scrolled completely behind the pinned header, the header animates its opacity from 0 to 1 and its (centered) "Settings" title appears. The fact that the header's opacity depends on the height of the title item - which is unknown until the list has been laid out - necessitates monitoring its SliverConstraints.scrollExtent from a scroll NotificationListener.
https://github.com/flutter/flutter/assets/1377460/539e2591-d0d7-4508-8ce8-4b8f587d7648
A sliver that shows its [child] when the user scrolls forward and hides it when the user scrolls backwards. Similar headers can be found in Google Photos and Facebook.
This sliver is preferable to the general purpose SliverPersistentHeader for its relatively narrow use case because there's no need to create a SliverPersistentHeaderDelegate or to predict the header's size.
https://github.com/flutter/flutter/assets/1377460/82b67dfb-5d38-4adf-9415-fc8527d0eb9f
Adds a new ScrollNotificationEnd example that demonstrates how to trigger an auto-scroll based on an individual sliver's `SliverConstraints` and `SliverGeometry`.
Then new example auto-scrolls one special "aligned item" sliver to the top or bottom of the viewport, whenever it's partially visible (because it overlaps the top or bottom of the viewport). This example differs from the existing ScrollEndNotification example because the layout of the to-be aligned sliver is retrieved from its `RenderSliver` via a
GlobalKey. The new example does not rely on all of the list items having the same extent.
A sliver that is pinned to the start of its `CustomScrollView` and reacts to scrolling by resizing between the intrinsic sizes of its min and max extent prototypes.
The minimum and maximum sizes of this sliver are defined by `minExtentPrototype` and `maxExtentPrototype`, a pair of widgets that are laid out once. You can use `SizedBox` widgets to define the size limits.
This sliver is preferable to the general purpose `SliverPersistentHeader` for its relatively narrow use case because there's no need to create a `SliverPersistentHeaderDelegate` or to predict the header's minimum or maximum size.
The sample shows how this sliver's two extent prototype properties can be used to create a resizing header whose minimum and maximum sizes match small and large configurations of the same header widget.
https://github.com/flutter/flutter/assets/1377460/fa7ced98-9d92-4d13-b093-50392118c213
Related sliver utility PRs: https://github.com/flutter/flutter/pull/143538, https://github.com/flutter/flutter/pull/143196, https://github.com/flutter/flutter/pull/127340.
This PR adds `AnimatedList.separated`. A widget like an AnimatedList with animated separators. `animated_list_separated.0.dart` extends `animated_list.0.dart` to work with `AnimatedList.separated`
Related issue: https://github.com/flutter/flutter/issues/48226
The scroll notification events reported for a press-drag-release gesture within a scrollable on a touch screen device begin with a `ScrollStartNotification`, followed by a series of `ScrollUpdateNotifications`, and conclude with a `ScrollEndNotification`. This protocol can be used to defer work until an interactive scroll gesture ends. For example, you might defer updating a scrollable's contents via network requests until the scroll has ended, or you might want to automatically auto-scroll at that time.
In the example that follows the CustomScrollView automatically scrolls so that the last partially visible fixed-height item is completely visible when the scroll gesture ends. Many iOS applications do this kind of thing. It only makes sense to auto-scroll when the user isn't actively dragging the scrollable around.
It's easy enough to do this by reacting to a ScrollEndNotifcation by auto-scrolling to align the last fixed-height list item ([source code](https://gist.github.com/HansMuller/13e2a7adadc9afb3803ba7848b20c410)).
https://github.com/flutter/flutter/assets/1377460/a6e6fc77-6742-4f98-81ba-446536535f73
Dragging the scrollbar thumb in a desktop application is a similar user gesture. Currently it's not possible to defer work or auto-scroll (or whatever) while the scrollable is actively being dragged via the scrollbar thumb because each scrollbar thumb motion is mapped to a scroll start - scroll update - scroll end series of notifications. On a desktop platform, the same code behaves quite differently when the scrollbar thumb is dragged.
https://github.com/flutter/flutter/assets/1377460/2593d8a3-639c-407f-80c1-6e6f67fb8c5f
The stream of scroll-end events triggers auto-scrolling every time the thumb moves. From the user's perspective this feels like a losing struggle.
One can also detect the beginning and end of a touch-drag by listening to the value of a ScrollPosition's `isScrollingNotifier`. This approach suffers from a similar problem: during a scrollbar thumb-drag, the `isScrollingNotifier` value isn't updated at all.
This PR refactors the RawScrollbar implementation to effectively use a ScrollDragController to manage scrolls caused by dragging the scrollbar's thumb. Doing so means that dragging the thumb will produce the same notifications as dragging the scrollable on a touch device.
Now desktop applications can choose to respond to scrollbar thumb drags in the same that they respond to drag scrolling on a touch screen. With the changes included here, the desktop or web version of the app works as expected, whether you're listing to scroll notifications or the scroll position's `isScrollingNotifier`.
https://github.com/flutter/flutter/assets/1377460/67435c40-a866-4735-a19b-e3d68eac8139
This PR also makes the second [ScrollPosition API doc example](https://api.flutter.dev/flutter/widgets/ScrollPosition-class.html#cupertino.ScrollPosition.2) work as expected when used with the DartPad that's part of API doc page.
Desktop applications also see scroll start-update-end notifications due to the mouse wheel. There is no touch screen analog for the mouse wheel, so an application that wanted to enable this kind of auto-scrolling alignment would have to include a heuristic that dealt with the sequence of small scrolls triggered by the mouse wheel. Here's an example of that: [source code](https://gist.github.com/HansMuller/ce5c474a458f5f4bcc07b0d621843165). This version of the app does not auto-align in response to small changes, wether they're triggered by dragging the scrollbar thumb of the mouse wheel.
Related sliver utility PRs: https://github.com/flutter/flutter/pull/143538, https://github.com/flutter/flutter/pull/143196, https://github.com/flutter/flutter/pull/143325.
Adds tests for `relative_positioned_transition`, `positioned_transition`, `sliver_fade_transition`, `align_transition`, `animated_builder`, `rotation_transition`, `animated_widget`, `slide_transition`, `listenable_builder`, `scale_transition`, `default_text_style_transition`, `decorated_box_transition`, `size_transition` api examples. Makes double type in the `align_transition` example explicit.
A test for `fade_transition` is already in currently open #148178.
Part of #130459.
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Updates `examples/api/lib/widgets/restoration_properties/restorable_value.0.dart` to meet the latest API examples structure
- Adds tests for `examples/api/lib/widgets/restoration_properties/restorable_value.0.dart`
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Updates `examples/api/lib/widgets/actions/actions.0.dart` to meet the latest API examples structure
- Adds tests for `examples/api/lib/widgets/actions/actions.0.dart`
### fixes#136139
<br>
<details open> <summary><b>getting sentimental in the PR description</b> (click to collapse)<br><br></summary>
The past 7 months have been quite the journeyâI made some huge blunders and some huge accomplishmentsâa very fun time overall.
I really appreciate the people who took the time to perform code review for my refactoring shenanigans: **christopherfujino**, **andrewkolos**, **LongCatIsLooong**, **gspencergoog**, **loic-sharma**, **Piinks**, **bernaferrari**, **bartekpacia**, **bleroux**, **kevmoo**, **rakudrama**, **XilaiZhang**, **QuncCccccc**, **MominRaza**, and **victorsanni**.
And a huge shoutout to 2 individuals:
- @justinmc, for offering to sponsor me for commit access (words could not describe my excitement)
- @goderbauer, for being super duper proactive and consistent with code review
<br>
</details>
This pull request makes 13 "switch statements â switch expressions" PRs in total, reducing the LOC in this repo by **1,974**!
From now on, I'll make sure to request a test exemption for each refactoring PR ð
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Updates `examples/api/lib/widgets/shared_app_data/shared_app_data.0.dart` to meet latest API examples structure
- Updates `examples/api/lib/widgets/shared_app_data/shared_app_data.1.dart` to meet latest API examples structure
- Adds tests for `examples/api/lib/widgets/shared_app_data/shared_app_data.0.dart`
- Adds tests for `examples/api/lib/widgets/shared_app_data/shared_app_data.1.dart`
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Adds disposal of the `CurvedAnimation` in `examples/api/test/widgets/transitions/fade_transition.0.dart`
- Adds tests for `examples/api/lib/widgets/transitions/fade_transition.0.dart`
*Use `super.key` instead of manually passing the `Key` parameter using super(key: key) in the constructors.*
Since if you create a widget the new default will use `super.key` instead of `Key? key : super(key: key)` this small change is to maintain the consistency, it has no semantic change
also there are some other places that might need to be updated:
this file for example generate l10n project and it has all the dart code as String, it might have tests that validate the output somewhere that I might miss, also there are some other places like the `_Segment` class where it require `ValueKey` instead if `Key` so I didn't update them (even though it's possible)
Reverts: flutter/flutter#148238
Initiated by: zanderso
Reason for reverting: Failures in post submit https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8748025189669617649/+/u/run_test.dart_for_web_canvaskit_tests_shard_and_subshard_3/stdout
Original PR Author: justinmc
Reviewed By: {hellohuanlin}
This change reverts the following previous change:
Reland of https://github.com/flutter/flutter/pull/143002, which was reverted in https://github.com/flutter/flutter/pull/148237 due to unresolved docs references. Not sure why those weren't caught in presubmit.
```
dartdoc:stdout: Generating docs for package flutter...
dartdoc:stderr: error: unresolved doc reference [TextInput.showSystemContextMenu]
dartdoc:stderr: from widgets.MediaQueryData.supportsShowingSystemContextMenu: (file:///b/s/w/ir/x/w/flutter/packages/flutter/lib/src/widgets/media_query.dart:579:14)
dartdoc:stderr: in documentation inherited from widgets.MediaQueryData.supportsShowingSystemContextMenu: (file:///b/s/w/ir/x/w/flutter/packages/flutter/lib/src/widgets/media_query.dart:579:14)
dartdoc:stderr: error: unresolved doc reference [showSystemContextMenu]
dartdoc:stderr: from services.SystemContextMenuController.hide: (file:///b/s/w/ir/x/w/flutter/packages/flutter/lib/src/services/text_input.dart:2554:16)
dartdoc:stderr: error: unresolved doc reference [hideSystemContextMenu]
dartdoc:stderr: from services.SystemContextMenuController.show: (file:///b/s/w/ir/x/w/flutter/packages/flutter/lib/src/services/text_input.dart:2509:16)
```
It's now possible to use the native-rendered text selection context menu on iOS. This sacrifices customizability in exchange for avoiding showing a notification when the user presses "Paste". It's off by default, but to enable, see the example system_context_menu.0.dart.
Reverts: flutter/flutter#143002
Initiated by: cbracken
Reason for reverting: unresolved docs links. See failure here: https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20docs_test/16540/overview
```
dartdoc:stdout: Generating docs for package flutter...
dartdoc:stderr: error: unresolved doc reference [TextInput.showSystemContextMenu]
dartdoc:stderr: from widgets.MediaQueryData.supportsShowingSystemContextMenu: (file:///b/s/w/ir/x/w/flutter/packages/flutt
Original PR Author: justinmc
Reviewed By: {Renzo-Olivares, hellohuanlin}
This change reverts the following previous change:
In order to work around the fact that iOS 15 shows a notification on pressing Flutter's paste button (https://github.com/flutter/flutter/issues/103163), this PR allows showing the iOS system context menu in text fields.
<img width="385" alt="Screenshot 2024-02-06 at 11 52 25 AM" src="https://github.com/flutter/flutter/assets/389558/d82e18ee-b8a3-4082-9225-cf47fa7f3674">
It is currently opt-in, which a user would typically do like this (also in example system_context_menu.0.dart):
```dart
contextMenuBuilder: (BuildContext context, EditableTextState editableTextState) {
// If supported, show the system context menu.
if (SystemContextMenu.isSupported(context)) {
return SystemContextMenu.editableText(
editableTextState: editableTextState,
);
}
// Otherwise, show the flutter-rendered context menu for the current
// platform.
return AdaptiveTextSelectionToolbar.editableText(
editableTextState: editableTextState,
);
},
```
Requires engine PR https://github.com/flutter/engine/pull/50095.
## API changes
### SystemContextMenu
A widget that shows the system context menu when built, and removes it when disposed. The main high-level way that most users would use this PR. Only works on later versions of iOS.
### SystemContextMenuController
Used under the hood to hide and show a system context menu. There can only be one visible at a time.
### MediaQuery.supportsShowingSystemContextMenu
Sent by the iOS embedder to tell the framework whether or not the platform supports showing the system context menu. That way the framework, or Flutter developers, can decide to show a different menu.
### `flutter/platform ContextMenu.showSystemContextMenu`
Sent by the framework to show the menu at a given `targetRect`, which is the current selection rect.
### `flutter/platform ContextMenu.hideSystemContextMenu`
Sent by the framework to hide the menu. Typically not needed, because the platform will hide the menu when the user taps outside of it and after the user presses a button, but it handles edge cases where the user programmatically rebuilds the context menu, for example.
### `flutter/platform System.onDismissSystemContextMenu`
Sent by the iOS embedder to indicate that the system context menu has been hidden by the system, such as when the user taps outside of the menu. This is useful when there are multiple instances of SystemContextMenu, such as with multiple text fields.
It's now possible to use the native-rendered text selection context menu on iOS. This sacrifices customizability in exchange for avoiding showing a notification when the user presses "Paste". It's off by default, but to enable, see the example system_context_menu.0.dart.
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Updates `examples/api/lib/widgets/animated_size/animated_size.0.dart` API example by using `SizedBox` to size the surrounding of the `FlutterLogo` while setting the constant `FlutterLogo` size. This was done because `FlutterLogo` already has size animation under the hood, and the main goal of this example is to show `AnimatedSize` usage
- Adds test for `examples/api/lib/widgets/animated_size/animated_size.0.dart`
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Updates `examples/api/lib/widgets/async/stream_builder.0.dart`
- Adds test for `examples/api/lib/widgets/async/stream_builder.0.dart`
This PR contributes to https://github.com/flutter/flutter/issues/130459
### Description
- Fixes name of the `examples/api/lib/widgets/shortcuts/single_activator.single_activator.0.dart`
- Adds tests for `examples/api/lib/widgets/shortcuts/single_activator.0.dart`
