Now the text input control knows how to move the caret when you tap
inside the string. There's still some rough edges to polish up, but this
patch is the first step.

Fixes #108

This patch teaches the editing system to paint reasonable selections for
single-line text fields, including for bidirectional text.

Requires https://github.com/flutter/engine/pull/2318

Now we recreate the stub every time we try to connect to the keyboard. The
underlying message pipe in the stub cannot be re-used, which is why we
previously asserted.

Fixes #776

Previously, EditableString had many public members because it needed to
implement the KeyboardClient interface. However, that's confusing
because these methods cannot be called directly.

Now EditableString holds a private implementation of the KeyboardClient,
which hides the implementation details.

Fixes #208
Fixes #209

We were getting the proper values, but we thought we were still composing, so
the text was still underlined.

Fixes #115

That way folks can customize it if they want (and it makes the code a
bit more self-documenting).

Now the label animates from its inline position to above the text and
the focus highlight grows into place.

RawEditableLine is now responsible for the scrolling behavior, which
removes the need for callbacks between RawEditableLine and Input. It
also fixes a bug whereby the whole Input widget (including its icon)
would scroll when the text got long.

Properly support labels, hints, icons, and custom typography.

Fixes #1308

This patch restructures how we size the editing region of the Input widget. Now
RenderEditableLine understands that it's a single-line editing widget and sizes
itself correctly.

Instead, require the developer to opt-in to autofocusing because autofocusing
can be disruptive.

Fixes #1307

Previously this code was in the animation layer, which didn't make much
sense because scrolling is a widget concern.

The dart bindings changed semantics in a non-compatible way.

Previously we used a positional argument for widgets that had multiple
children. Now we use a named argument that defaults to an empty list.

Fixes #241

We use the ScrollDirection for more than just scrolling.

Fixes #151

Require a Key on Input.

Simplify the API for Focus.at() and Focus.moveTo().
Fixes #236.
This will require an e-mail to flutter-dev.

Make Input grab focus onTap not onPointerDown.
Fixes #189.

Complain when you use Focus.at() with two different GlobalKeys that
are both in the tree at the same time.
Fixes #181.

Add dartdocs for Focus.moveTo() and Focus.moveScopeTo().

After this patch, if you try to use a widget that depends on being enclosed in
a material, you now get an assert and a debugPrint if you're not inside a
material.

Fixes #243

Also, handle the case of "dense" input widgets that have less margin.

Fixes #626

This feature can be used to implement password fields, where the user doesn't
want the text displayed on screen. Currently all the characters are hidden.
Eventualy we'll want to show the most recent character for some timeout.

Fixes #636

The input widget scrolls, so it should give its text loose constraints.  That
way the text ends up being its intrinsic size even if put in a context with
tight constraints.

Fixes #298

Make Radio widgets take a type that describes the type of their value,
so that you can catch when you use the wrong value.

Standardise on ValueChanged<Foo> instead of having a FooValueChanged
for every value of Foo.

If the text is empty, the IME may call deleteSurroundingText(1, 0) if the user
hits the delete key.  The selection should remain at position 0 if this
happens.

The style we use for callbacks in widgets is "onFoo". These classes were using
an order naming convention and just called their callbacks "callback".

The goal is to follow the guidelines in
https://github.com/flutter/engine/blob/master/sky/specs/style-guide.md#packages

Fixes #1638

Also add an input widget API for the keyboard submit button

Add type annotations in many places.
Fix some identifiers to have more lint-satisfying names.
Make all operator==s consistent in style.
Reorder some functions for consistency.
Make ParentData no longer dynamic, and fix all the code around that.

These are now part of material.dart.

In the vast majority of cases, folks should be interacting with the Widget
rather than its State.

Fixes #267

Focus.at() and company should be on Focus, not FocusState.

_notifyDescendants() was using the wrong runtimeType.

Let InheritedWidget update the descendants during build.

When you setState() during build, assert that you're not
markNeedsBuild()ing someone who isn't a descendant.

Typo in Widget.toString().

Fixes #1372

This updates to mojo 4e4d51ce28a and mojo sdk 711a0bcfb141b4 and updates the sky
package's pubspec.yaml dependency to '>=0.1.0 <0.2.0' to be compatible with
the current mojo package. This includes an update to the Mojo Dart generator to
produce real classes for enums and the corresponding updates for users of the
KeyboardType enum in Sky as well as one scoped_ptr->std::unique_ptr in shell
corresponding to a change in the Mojo EDK.

When a new version of the sky and sky_services package are pushed this will fix
domokit/mojo#440.

All the use cases for EventDisposition are now addressed by the gesture
detection system.

What's important about this code is that it's presenting services outside the
VM, not the particular technology used to present the services.

The editing directory just defined two widgets. We might as well fold them into
the main widgets library.

Code outside of package:sky should import this code using

package:sky/rendering.dart
package:sky/widgets.dart

Moving this code into the "src" directory is a convention that signifies that
and it cleans up the generated dartdoc because the libraries in the src
directory aren't included in the generated documentation. Instead, the classes
are documented in the widgets.dart and rendering.dart libraries.