copy Flutter sources about LayerLink and its friends

lib/src/custom_follower.dart

@@ -6,6 +6,7 @@ import 'package:flutter/widgets.dart';
 import 'package:vector_math/vector_math_64.dart';
 
 import 'anchor.dart';
+import 'flutter_src/layer.dart';
 import 'portal.dart';
 
 /// @nodoc
@@ -24,7 +25,7 @@ class CustomCompositedTransformFollower extends SingleChildRenderObjectWidget {
   final Anchor anchor;
 
   /// @nodoc
-  final LayerLink link;
+  final MyLayerLink link;
 
   /// @nodoc
   final OverlayLink overlayLink;
@@ -58,7 +59,7 @@ class CustomCompositedTransformFollower extends SingleChildRenderObjectWidget {
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(DiagnosticsProperty<Anchor>('anchor', anchor));
-    properties.add(DiagnosticsProperty<LayerLink>('link', link));
+    properties.add(DiagnosticsProperty<MyLayerLink>('link', link));
     properties
         .add(DiagnosticsProperty<OverlayLink>('overlayLink', overlayLink));
     properties.add(DiagnosticsProperty<Size>('targetSize', targetSize));
@@ -70,7 +71,7 @@ class CustomCompositedTransformFollower extends SingleChildRenderObjectWidget {
 class CustomRenderFollowerLayer extends RenderProxyBox {
   /// @nodoc
   CustomRenderFollowerLayer({
-    required LayerLink link,
+    required MyLayerLink link,
     required OverlayLink overlayLink,
     required Size targetSize,
     required Anchor anchor,
@@ -93,12 +94,12 @@ class CustomRenderFollowerLayer extends RenderProxyBox {
     }
   }
 
-  LayerLink _link;
+  MyLayerLink _link;
 
   /// @nodoc
-  LayerLink get link => _link;
+  MyLayerLink get link => _link;
 
-  set link(LayerLink value) {
+  set link(MyLayerLink value) {
     if (_link == value) {
       return;
     }
@@ -170,7 +171,7 @@ class CustomRenderFollowerLayer extends RenderProxyBox {
   /// [PortalTarget].
   ///
   /// The reason we cannot simply access the [link]'s leader in [paint] is that
-  /// the leader is only attached to the [LayerLink] in [LeaderLayer.attach],
+  /// the leader is only attached to the [MyLayerLink] in [LeaderLayer.attach],
   /// which is called in the compositing phase which is after the paint phase.
   Offset _computeLinkedOffset(Offset leaderOffset) {
     assert(
@@ -234,7 +235,7 @@ class CustomRenderFollowerLayer extends RenderProxyBox {
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
-    properties.add(DiagnosticsProperty<LayerLink>('link', link));
+    properties.add(DiagnosticsProperty<MyLayerLink>('link', link));
     properties
         .add(DiagnosticsProperty<OverlayLink>('overlayLink', overlayLink));
     properties.add(
@@ -266,7 +267,7 @@ class _CustomFollowerLayer extends ContainerLayer {
     required this.linkedOffsetCallback,
   });
 
-  LayerLink link;
+  MyLayerLink link;
 
   /// Callback that is called to compute the linked offset of the follower layer
   /// based on the `leaderOffset` of the leader layer.
@@ -457,7 +458,7 @@ class _CustomFollowerLayer extends ContainerLayer {
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
-    properties.add(DiagnosticsProperty<LayerLink>('link', link));
+    properties.add(DiagnosticsProperty<MyLayerLink>('link', link));
     properties.add(
         TransformProperty('transform', getLastTransform(), defaultValue: null));
     properties.add(DiagnosticsProperty<Offset Function(Offset leaderOffset)>(

lib/src/flutter_src/basic.dart

@@ -0,0 +1,57 @@
+// ignore_for_file: unnecessary_null_comparison, diagnostic_describe_all_properties
+
+import 'package:flutter/material.dart';
+import 'package:flutter/rendering.dart';
+import 'layer.dart';
+import 'proxy_box.dart';
+
+/// A widget that can be targeted by a [CompositedTransformFollower].
+///
+/// When this widget is composited during the compositing phase (which comes
+/// after the paint phase, as described in [WidgetsBinding.drawFrame]), it
+/// updates the [link] object so that any [CompositedTransformFollower] widgets
+/// that are subsequently composited in the same frame and were given the same
+/// [LayerLink] can position themselves at the same screen location.
+///
+/// A single [MyCompositedTransformTarget] can be followed by multiple
+/// [CompositedTransformFollower] widgets.
+///
+/// The [MyCompositedTransformTarget] must come earlier in the paint order than
+/// any linked [CompositedTransformFollower]s.
+///
+/// See also:
+///
+///  * [CompositedTransformFollower], the widget that can target this one.
+///  * [LeaderLayer], the layer that implements this widget's logic.
+class MyCompositedTransformTarget extends SingleChildRenderObjectWidget {
+  /// Creates a composited transform target widget.
+  ///
+  /// The [link] property must not be null, and must not be currently being used
+  /// by any other [MyCompositedTransformTarget] object that is in the tree.
+  const MyCompositedTransformTarget({
+    Key? key,
+    required this.link,
+    Widget? child,
+  }) : assert(link != null),
+        super(key: key, child: child);
+
+  /// The link object that connects this [MyCompositedTransformTarget] with one or
+  /// more [CompositedTransformFollower]s.
+  ///
+  /// This property must not be null. The object must not be associated with
+  /// another [MyCompositedTransformTarget] that is also being painted.
+  final MyLayerLink link;
+
+  @override
+  MyRenderLeaderLayer createRenderObject(BuildContext context) {
+    return MyRenderLeaderLayer(
+      link: link,
+    );
+  }
+
+  @override
+  void updateRenderObject(BuildContext context, MyRenderLeaderLayer renderObject) {
+    renderObject.link = link;
+  }
+}
+