Add supported fields in FixedTimeline

lib/src/timelines.dart

@@ -302,6 +302,10 @@ class FixedTimeline extends StatelessWidget {
     @required TimelineTileBuilder builder,
     TimelineThemeData theme,
     Axis direction,
+    MainAxisSize mainAxisSize = MainAxisSize.max,
+    TextDirection textDirection,
+    VerticalDirection verticalDirection = VerticalDirection.down,
+    Clip clipBehavior = Clip.none,
   }) {
     assert(builder != null);
     // TODO: how remove Builders?
@@ -314,22 +318,127 @@ class FixedTimeline extends StatelessWidget {
       ],
       theme: theme,
       direction: direction,
+      mainAxisSize: mainAxisSize,
+      textDirection: textDirection,
+      verticalDirection: verticalDirection,
+      clipBehavior: clipBehavior,
     );
   }
 
   /// Creates a timeline flex layout.
+  ///
+  /// The [direction], [mainAxisAlignment], [crossAxisAlignment], and
+  /// [verticalDirection] arguments must not be null. If [crossAxisAlignment] is
+  /// [CrossAxisAlignment.baseline], then [textBaseline] must not be null.
+  ///
+  /// The [textDirection] argument defaults to the ambient [Directionality], if
+  /// any. If there is no ambient directionality, and a text direction is going
+  /// to be necessary to decide which direction to lay the children in or to
+  /// disambiguate `start` or `end` values for the main or cross axis
+  /// directions, the [textDirection] must not be null.
   const FixedTimeline({
     Key key,
     this.theme,
     this.direction,
+    this.mainAxisSize = MainAxisSize.max,
+    this.textDirection,
+    this.verticalDirection = VerticalDirection.down,
+    this.clipBehavior = Clip.none,
     this.children = const [],
   })  : assert(direction == null || theme == null, 'Cannot provide both a direction and a theme.'),
+        assert(mainAxisSize != null),
+        assert(verticalDirection != null),
+        assert(clipBehavior != null),
         super(key: key);
 
+  /// Default visual properties, like colors, size and spaces, for this timeline's component widgets.
+  ///
+  /// The default value of this property is the value of [TimelineThemeData.vertical()].
   final TimelineThemeData theme;
+
+  /// The direction to use as the main axis.
   final Axis direction;
+
+  /// The widgets below this widget in the tree.
+  ///
+  /// If this list is going to be mutated, it is usually wise to put a [Key] on
+  /// each of the child widgets, so that the framework can match old
+  /// configurations to new configurations and maintain the underlying render
+  /// objects.
+  ///
+  /// See also:
+  ///
+  ///  * [MultiChildRenderObjectWidget.children]
   final List<Widget> children;
 
+  /// How much space should be occupied in the main axis.
+  ///
+  /// After allocating space to children, there might be some remaining free
+  /// space. This value controls whether to maximize or minimize the amount of
+  /// free space, subject to the incoming layout constraints.
+  ///
+  /// If some children have a non-zero flex factors (and none have a fit of
+  /// [FlexFit.loose]), they will expand to consume all the available space and
+  /// there will be no remaining free space to maximize or minimize, making this
+  /// value irrelevant to the final layout.
+  final MainAxisSize mainAxisSize;
+
+  /// Determines the order to lay children out horizontally and how to interpret
+  /// `start` and `end` in the horizontal direction.
+  ///
+  /// Defaults to the ambient [Directionality].
+  ///
+  /// If [textDirection] is [TextDirection.rtl], then the direction in which
+  /// text flows starts from right to left. Otherwise, if [textDirection] is
+  /// [TextDirection.ltr], then the direction in which text flows starts from
+  /// left to right.
+  ///
+  /// If the [direction] is [Axis.horizontal], this controls the order in which
+  /// the children are positioned (left-to-right or right-to-left), and the
+  /// meaning of the [mainAxisAlignment] property's [MainAxisAlignment.start] and
+  /// [MainAxisAlignment.end] values.
+  ///
+  /// If the [direction] is [Axis.horizontal], and either the
+  /// [mainAxisAlignment] is either [MainAxisAlignment.start] or
+  /// [MainAxisAlignment.end], or there's more than one child, then the
+  /// [textDirection] (or the ambient [Directionality]) must not be null.
+  ///
+  /// If the [direction] is [Axis.vertical], this controls the meaning of the
+  /// [crossAxisAlignment] property's [CrossAxisAlignment.start] and
+  /// [CrossAxisAlignment.end] values.
+  ///
+  /// If the [direction] is [Axis.vertical], and the [crossAxisAlignment] is
+  /// either [CrossAxisAlignment.start] or [CrossAxisAlignment.end], then the
+  /// [textDirection] (or the ambient [Directionality]) must not be null.
+  final TextDirection textDirection;
+
+  /// Determines the order to lay children out vertically and how to interpret
+  /// `start` and `end` in the vertical direction.
+  ///
+  /// Defaults to [VerticalDirection.down].
+  ///
+  /// If the [direction] is [Axis.vertical], this controls which order children
+  /// are painted in (down or up), the meaning of the [mainAxisAlignment]
+  /// property's [MainAxisAlignment.start] and [MainAxisAlignment.end] values.
+  ///
+  /// If the [direction] is [Axis.vertical], and either the [mainAxisAlignment]
+  /// is either [MainAxisAlignment.start] or [MainAxisAlignment.end], or there's
+  /// more than one child, then the [verticalDirection] must not be null.
+  ///
+  /// If the [direction] is [Axis.horizontal], this controls the meaning of the
+  /// [crossAxisAlignment] property's [CrossAxisAlignment.start] and
+  /// [CrossAxisAlignment.end] values.
+  ///
+  /// If the [direction] is [Axis.horizontal], and the [crossAxisAlignment] is
+  /// either [CrossAxisAlignment.start] or [CrossAxisAlignment.end], then the
+  /// [verticalDirection] must not be null.
+  final VerticalDirection verticalDirection;
+
+  /// {@macro flutter.material.Material.clipBehavior}
+  ///
+  /// Defaults to [Clip.none].
+  final Clip clipBehavior;
+
   @override
   Widget build(BuildContext context) {
     final direction = this.direction ?? theme?.direction ?? Axis.vertical;
@@ -341,6 +450,10 @@ class FixedTimeline extends StatelessWidget {
       child: Flex(
         direction: direction,
         children: children,
+        mainAxisSize: mainAxisSize,
+        textDirection: textDirection,
+        verticalDirection: verticalDirection,
+        clipBehavior: clipBehavior,
       ),
     );
   }