This bug lists changes we'll probably never make, but should consider if we ever for some reason decided to start over in a new universe.

Foundation

• ChangeNotifier and Listenable and company are a bit mixed up. We could refactor the code here so that we more clearly have a Listenable and a ListenableController, and a ValueListenable and a ValueListenableController, and so on.

Services

• StandardMessageCodec should be a static class or should be stateful.
• dev.flutter/channel-buffers control messages should use a more efficient binary format rather than an inefficient bespoke \r-delimited text-based format.
• flutter/system, flutter/navigation, etc, control messages should use a more efficient binary format rather than JSON.

Painting

• addListener/removeListener on ImageStream have a broken API that should be redesigned.
• NotchedShape should be a shape, or should have another name.
• TextStyle has many decoration properties, it would be nice if they were all in one object, maybe separate objects for underline and overline and strike-through.

Gestures

• Rename PointerMoveEvent to PointerUpdateEvent, because it's also triggered at button changes without moves.

Animation

• Tweens should be immutable.
• Consider renaming vsync in AnimationController to tickerProvider (Roll engine c41bbc63d955cc7056a162957ac4eeeca6647dc2..e77e4f0e051cb53754814ffe33df291a551bdba3 (5 commits) #37255)
• Instead of one AnimationController, have one for each type of controller (bounded, unbounded, simulation, repeating, etc).
• Remove Animatable.animate in favour of Animation.drive.
• CurveTween constructor's argument should be positional. (Make CurveTween curve a regular parameter #21433)

Rendering

• Adaptor -> Adapter
• SliverChildListDelegate should have a children argument instead of a positional one
• CustomPainter.hitTest should take a Size argument (CustomPainter.hitTest missing size argument #28206)
• Layer.pushLayer should be renamed to withLayer, since it is not matched by a popLayer. The same applies to its relatives.
• BlendMode.srcATop -> BlendMode.srcAtop
• BlendMode.dstATop -> BlendMode.dstAtop

Widgets

• TabController should be a ValueListenable
• Rename WidgetBuilder to make it clear it's a typedef.
• Rename TransitionBuilder to make it clear it's a typedef with a child.
• Rename AnimatedBuilder to make it clear it takes any Listenable (even AnimationBuilder would be more consistent...), see also: Breaking changes that would improve the overall API #24722 (comment).
• Rename Listener to be PointerListener
• (Subclasses of) AnimatedWidget and ImplicitlyAnimatedWidget should be named consistently (see Breaking changes that would improve the overall API #24722 (comment)).
• Name the Foo vs FooTransition vs AnimatedFoo widgets more consistently (e.g. FadeTransition vs AnimatedOpacity, also AnimatedSize).
• Consider merging all the one-argument FooBuilder typedefs into one generic typedef, or otherwise cleaning up the inconsistencies there.
• inheritFromWidgetOfExactType should be generic rather than taking a Type (so it can guarantee its return type is of the same type as the argument).
• Container's width and height properties should size the child, and imply an alignment.
• It's weird that we have both showDialog and showGeneralDialog.
• AnimatedList should be AnimatedListView.
• SliverMultiBoxAdaptorWidget is not an adaptor; consider naming like SliverMultiChildRenderObjectWidget.
• Rename RichText to RawText.
• Change the type of maxLines from int to double (TextField maxLines should be a double, not an int. #35064).
• ColorFiltered -> ColorFilter
• Be consistent about callback parameter names for tapping/pressing something (onTap vs onPressed, Be consistent about callback parameter names for tapping/pressing something #17407)
• FocusNode and FocusScopeNode should use 'focusable' instead of 'canRequestFocus' as the attribute for controlling focusability.
• MediaQueryData.disableAnimations should be called MediaQueryData.enableAnimations with the opposite semantics (see style guide under "double negatives").
• MediaQuery.viewPadding should be used instead of MediaQuery.padding throughout the framework. viewPadding was added ATF to address edge cases, but the API surface has become confusing as a result, see SafeArea.maintainBottomViewPadding should be true by default #59204
• Element.activate should rename to Element.reactivate, because only the reactivate will callback.
• OnInvokeCallback should be called just InvokeCallback per the style guide.
• Navigator: reportsRouteUpdateToEngine should be reportRouteUpdateToEngine (imperative not descriptive).
• Better property's naming for Form widget (autoValidateMode, instead of autovalidateMode) #115820

Material

• ColorScheme.on* shouldn't look like event handlers
• Handle the tap target padding for e.g. mini fabs more intuitively (dunno what that would entail exactly)
• InputDecoration.filled should be isFilled
• InputDecoration should only have one prefix field and one suffix field, rather than three each (widget, icon, text). And it probably should have an error, a label, and a hint instead of just errorText, labelText, and hintText.
• Change Divider and VerticalDivider's indent and endIndent properties to simply be margin
• Colors.grey -> Colors.gray