[rename fixit] scrollDirection -> mainAxis

Fixes #581

packages/flutter/lib/src/material/tabs.dart

@@ -784,7 +784,7 @@ class _TabBarState<T> extends ScrollableState<TabBar<T>> implements TabBarSelect
 
     if (config.isScrollable) {
       return new Viewport(
-        scrollDirection: Axis.horizontal,
+        mainAxis: Axis.horizontal,
         paintOffset: scrollOffsetToPixelDelta(scrollOffset),
         onPaintOffsetUpdateNeeded: _handlePaintOffsetUpdateNeeded,
         child: contents
@@ -961,7 +961,7 @@ class _TabBarViewState<T> extends PageableListState<TabBarView<T>> implements Ta
       _initSelection(newSelection);
     return new PageViewport(
       itemsWrap: config.itemsWrap,
-      scrollDirection: config.scrollDirection,
+      mainAxis: config.scrollDirection,
       startOffset: scrollOffset,
       overlayPainter: config.scrollableListPainter,
       children: _items

packages/flutter/lib/src/rendering/block.dart

@@ -28,14 +28,14 @@ typedef double _Constrainer(double value);
 abstract class RenderBlockBase extends RenderBox
     with ContainerRenderObjectMixin<RenderBox, BlockParentData>,
          RenderBoxContainerDefaultsMixin<RenderBox, BlockParentData>
-    implements HasScrollDirection {
+    implements HasMainAxis {
 
   RenderBlockBase({
     List<RenderBox> children,
-    Axis direction: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     double itemExtent,
     double minExtent: 0.0
-  }) : _direction = direction, _itemExtent = itemExtent, _minExtent = minExtent {
+  }) : _mainAxis = mainAxis, _itemExtent = itemExtent, _minExtent = minExtent {
     addAll(children);
   }
 
@@ -45,11 +45,11 @@ abstract class RenderBlockBase extends RenderBox
   }
 
   /// The direction to use as the main axis.
-  Axis get direction => _direction;
-  Axis _direction;
-  void set direction (Axis value) {
-    if (_direction != value) {
-      _direction = value;
+  Axis get mainAxis => _mainAxis;
+  Axis _mainAxis;
+  void set mainAxis (Axis value) {
+    if (_mainAxis != value) {
+      _mainAxis = value;
       markNeedsLayout();
     }
   }
@@ -75,9 +75,7 @@ abstract class RenderBlockBase extends RenderBox
   }
 
   /// Whether the main axis is vertical.
-  bool get isVertical => _direction == Axis.vertical;
-
-  Axis get scrollDirection => _direction;
+  bool get isVertical => _mainAxis == Axis.vertical;
 
   BoxConstraints _getInnerConstraints(BoxConstraints constraints) {
     if (isVertical)
@@ -117,7 +115,7 @@ abstract class RenderBlockBase extends RenderBox
 
   void debugFillDescription(List<String> description) {
     super.debugFillDescription(description);
-    description.add('direction: $direction');
+    description.add('mainAxis: $mainAxis');
   }
 }
 
@@ -126,10 +124,10 @@ class RenderBlock extends RenderBlockBase {
 
   RenderBlock({
     List<RenderBox> children,
-    Axis direction: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     double itemExtent,
     double minExtent: 0.0
-  }) : super(children: children, direction: direction, itemExtent: itemExtent, minExtent: minExtent);
+  }) : super(children: children, mainAxis: mainAxis, itemExtent: itemExtent, minExtent: minExtent);
 
   double _getIntrinsicCrossAxis(BoxConstraints constraints, _ChildSizingFunction childSize, _Constrainer constrainer) {
     double extent = 0.0;
@@ -242,7 +240,7 @@ class RenderBlockViewport extends RenderBlockBase {
     ExtentCallback maxCrossAxisDimensionCallback,
     ExtentCallback minCrossAxisDimensionCallback,
     Painter overlayPainter,
-    Axis direction: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     double itemExtent,
     double minExtent: 0.0,
     double startOffset: 0.0,
@@ -253,7 +251,7 @@ class RenderBlockViewport extends RenderBlockBase {
        _minCrossAxisExtentCallback = minCrossAxisDimensionCallback,
        _overlayPainter = overlayPainter,
        _startOffset = startOffset,
-       super(children: children, direction: direction, itemExtent: itemExtent, minExtent: minExtent);
+       super(children: children, mainAxis: mainAxis, itemExtent: itemExtent, minExtent: minExtent);
 
   bool _inCallback = false;
   bool get isRepaintBoundary => true;

packages/flutter/lib/src/rendering/grid.dart

@@ -384,13 +384,13 @@ class RenderGrid extends RenderVirtualViewport<GridParentData> {
     _delegate = newDelegate;
   }
 
-  void set scrollDirection(Axis value) {
+  void set mainAxis(Axis value) {
     assert(() {
       if (value != Axis.vertical)
         throw new RenderingError('RenderGrid doesn\'t yet support horizontal scrolling.');
       return true;
     });
-    super.scrollDirection = value;
+    super.mainAxis = value;
   }
 
   int get virtualChildCount => super.virtualChildCount ?? childCount;

packages/flutter/lib/src/rendering/list.dart

@@ -18,7 +18,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
     EdgeDims padding,
     int virtualChildCount,
     Offset paintOffset: Offset.zero,
-    Axis scrollDirection: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     Painter overlayPainter,
     LayoutCallback callback
   }) : _itemExtent = itemExtent,
@@ -26,7 +26,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
        super(
          virtualChildCount: virtualChildCount,
          paintOffset: paintOffset,
-         scrollDirection: scrollDirection,
+         mainAxis: mainAxis,
          overlayPainter: overlayPainter,
          callback: callback
        ) {
@@ -58,7 +58,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
   }
 
   double get _scrollAxisPadding {
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.vertical:
         return padding.vertical;
       case Axis.horizontal:
@@ -80,7 +80,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
 
   double _getIntrinsicWidth(BoxConstraints constraints) {
     assert(constraints.debugAssertIsNormalized);
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.vertical:
         return constraints.constrainWidth(0.0);
       case Axis.horizontal:
@@ -98,7 +98,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
 
   double _getIntrinsicHeight(BoxConstraints constraints) {
     assert(constraints.debugAssertIsNormalized);
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.vertical:
         return constraints.constrainHeight(_preferredExtent);
       case Axis.horizontal:
@@ -115,7 +115,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
   }
 
   void performLayout() {
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.vertical:
         size = new Size(constraints.maxWidth,
                         constraints.constrainHeight(_preferredExtent));
@@ -138,7 +138,7 @@ class RenderList extends RenderVirtualViewport<ListParentData> {
     double y = 0.0;
     double dy = 0.0;
 
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.vertical:
         itemWidth = math.max(0.0, size.width - (padding == null ? 0.0 : padding.horizontal));
         itemHeight = itemExtent ?? size.height;

packages/flutter/lib/src/rendering/viewport.dart

@@ -71,9 +71,9 @@ class ViewportDimensions {
 }
 
 /// An interface that indicates that an object has a scroll direction.
-abstract class HasScrollDirection {
+abstract class HasMainAxis {
   /// Whether this object scrolls horizontally or vertically.
-  Axis get scrollDirection;
+  Axis get mainAxis;
 }
 
 /// A base class for render objects that are bigger on the inside.
@@ -81,19 +81,19 @@ abstract class HasScrollDirection {
 /// This class holds the common fields for viewport render objects but does not
 /// have a child model. See [RenderViewport] for a viewport with a single child
 /// and [RenderVirtualViewport] for a viewport with multiple children.
-class RenderViewportBase extends RenderBox implements HasScrollDirection {
+class RenderViewportBase extends RenderBox implements HasMainAxis {
   RenderViewportBase(
     Offset paintOffset,
-    Axis scrollDirection,
+    Axis mainAxis,
     ViewportAnchor scrollAnchor,
     Painter overlayPainter
   ) : _paintOffset = paintOffset,
-      _scrollDirection = scrollDirection,
+      _mainAxis = mainAxis,
       _scrollAnchor = scrollAnchor,
       _overlayPainter = overlayPainter {
     assert(paintOffset != null);
-    assert(scrollDirection != null);
-    assert(_offsetIsSane(_paintOffset, scrollDirection));
+    assert(mainAxis != null);
+    assert(_offsetIsSane(_paintOffset, mainAxis));
   }
 
   bool _offsetIsSane(Offset offset, Axis direction) {
@@ -107,14 +107,14 @@ class RenderViewportBase extends RenderBox implements HasScrollDirection {
 
   /// The offset at which to paint the child.
   ///
-  /// The offset can be non-zero only in the [scrollDirection].
+  /// The offset can be non-zero only in the [mainAxis].
   Offset get paintOffset => _paintOffset;
   Offset _paintOffset;
   void set paintOffset(Offset value) {
     assert(value != null);
     if (value == _paintOffset)
       return;
-    assert(_offsetIsSane(value, scrollDirection));
+    assert(_offsetIsSane(value, mainAxis));
     _paintOffset = value;
     markNeedsPaint();
     markNeedsSemanticsUpdate();
@@ -125,14 +125,14 @@ class RenderViewportBase extends RenderBox implements HasScrollDirection {
   /// If the viewport is scrollable in a particular direction (e.g., vertically),
   /// the child is given layout constraints that are fully unconstrainted in
   /// that direction (e.g., the child can be as tall as it wants).
-  Axis get scrollDirection => _scrollDirection;
-  Axis _scrollDirection;
-  void set scrollDirection(Axis value) {
+  Axis get mainAxis => _mainAxis;
+  Axis _mainAxis;
+  void set mainAxis(Axis value) {
     assert(value != null);
-    if (value == _scrollDirection)
+    if (value == _mainAxis)
       return;
     assert(_offsetIsSane(_paintOffset, value));
-    _scrollDirection = value;
+    _mainAxis = value;
     markNeedsLayout();
   }
 
@@ -198,7 +198,7 @@ class RenderViewportBase extends RenderBox implements HasScrollDirection {
   void debugFillDescription(List<String> description) {
     super.debugFillDescription(description);
     description.add('paintOffset: $paintOffset');
-    description.add('scrollDirection: $scrollDirection');
+    description.add('mainAxis: $mainAxis');
     description.add('scrollAnchor: $scrollAnchor');
     if (overlayPainter != null)
       description.add('overlay painter: $overlayPainter');
@@ -218,11 +218,11 @@ class RenderViewport extends RenderViewportBase with RenderObjectWithChildMixin<
   RenderViewport({
     RenderBox child,
     Offset paintOffset: Offset.zero,
-    Axis scrollDirection: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     ViewportAnchor scrollAnchor: ViewportAnchor.start,
     Painter overlayPainter,
     this.onPaintOffsetUpdateNeeded
-  }) : super(paintOffset, scrollDirection, scrollAnchor, overlayPainter) {
+  }) : super(paintOffset, mainAxis, scrollAnchor, overlayPainter) {
     this.child = child;
   }
 
@@ -232,7 +232,7 @@ class RenderViewport extends RenderViewportBase with RenderObjectWithChildMixin<
 
   BoxConstraints _getInnerConstraints(BoxConstraints constraints) {
     BoxConstraints innerConstraints;
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.horizontal:
         innerConstraints = constraints.heightConstraints();
         break;
@@ -338,12 +338,12 @@ abstract class RenderVirtualViewport<T extends ContainerBoxParentDataMixin<Rende
     int virtualChildCount,
     LayoutCallback callback,
     Offset paintOffset: Offset.zero,
-    Axis scrollDirection: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     ViewportAnchor scrollAnchor: ViewportAnchor.start,
     Painter overlayPainter
   }) : _virtualChildCount = virtualChildCount,
        _callback = callback,
-       super(paintOffset, scrollDirection, scrollAnchor, overlayPainter);
+       super(paintOffset, mainAxis, scrollAnchor, overlayPainter);
 
   int get virtualChildCount => _virtualChildCount;
   int _virtualChildCount;

packages/flutter/lib/src/widgets/basic.dart

@@ -832,19 +832,19 @@ class Viewport extends OneChildRenderObjectWidget {
   Viewport({
     Key key,
     this.paintOffset: Offset.zero,
-    this.scrollDirection: Axis.vertical,
+    this.mainAxis: Axis.vertical,
     this.scrollAnchor: ViewportAnchor.start,
     this.overlayPainter,
     this.onPaintOffsetUpdateNeeded,
     Widget child
   }) : super(key: key, child: child) {
-    assert(scrollDirection != null);
+    assert(mainAxis != null);
     assert(paintOffset != null);
   }
 
   /// The offset at which to paint the child.
   ///
-  /// The offset can be non-zero only in the [scrollDirection].
+  /// The offset can be non-zero only in the [mainAxis].
   final Offset paintOffset;
 
   /// The direction in which the child is permitted to be larger than the viewport
@@ -852,7 +852,7 @@ class Viewport extends OneChildRenderObjectWidget {
   /// If the viewport is scrollable in a particular direction (e.g., vertically),
   /// the child is given layout constraints that are fully unconstrainted in
   /// that direction (e.g., the child can be as tall as it wants).
-  final Axis scrollDirection;
+  final Axis mainAxis;
 
   final ViewportAnchor scrollAnchor;
 
@@ -866,7 +866,7 @@ class Viewport extends OneChildRenderObjectWidget {
   RenderViewport createRenderObject(BuildContext context) {
     return new RenderViewport(
       paintOffset: paintOffset,
-      scrollDirection: scrollDirection,
+      mainAxis: mainAxis,
       scrollAnchor: scrollAnchor,
       onPaintOffsetUpdateNeeded: onPaintOffsetUpdateNeeded,
       overlayPainter: overlayPainter
@@ -874,9 +874,9 @@ class Viewport extends OneChildRenderObjectWidget {
   }
 
   void updateRenderObject(BuildContext context, RenderViewport renderObject) {
-    // Order dependency: RenderViewport validates scrollOffset based on scrollDirection.
+    // Order dependency: RenderViewport validates scrollOffset based on mainAxis.
     renderObject
-      ..scrollDirection = scrollDirection
+      ..mainAxis = mainAxis
       ..scrollAnchor = scrollAnchor
       ..paintOffset = paintOffset
       ..onPaintOffsetUpdateNeeded = onPaintOffsetUpdateNeeded
@@ -1006,18 +1006,18 @@ class BlockBody extends MultiChildRenderObjectWidget {
   BlockBody({
     Key key,
     List<Widget> children: _emptyWidgetList,
-    this.direction: Axis.vertical
+    this.mainAxis: Axis.vertical
   }) : super(key: key, children: children) {
-    assert(direction != null);
+    assert(mainAxis != null);
   }
 
   /// The direction to use as the main axis.
-  final Axis direction;
+  final Axis mainAxis;
 
-  RenderBlock createRenderObject(BuildContext context) => new RenderBlock(direction: direction);
+  RenderBlock createRenderObject(BuildContext context) => new RenderBlock(mainAxis: mainAxis);
 
   void updateRenderObject(BuildContext context, RenderBlock renderObject) {
-    renderObject.direction = direction;
+    renderObject.mainAxis = mainAxis;
   }
 }
 

packages/flutter/lib/src/widgets/mixed_viewport.dart

@@ -144,7 +144,7 @@ class _MixedViewportElement extends RenderObjectElement {
   void mount(Element parent, dynamic newSlot) {
     super.mount(parent, newSlot);
     renderObject
-      ..direction = widget.direction
+      ..mainAxis = widget.direction
       ..callback = layout
       ..postLayoutCallback = postLayout
       ..totalExtentCallback = _noIntrinsicExtent
@@ -181,7 +181,7 @@ class _MixedViewportElement extends RenderObjectElement {
   void update(MixedViewport newWidget) {
     _ChangeDescription changes = newWidget.evaluateChangesFrom(widget);
     super.update(newWidget);
-    renderObject.direction = widget.direction;
+    renderObject.mainAxis = widget.direction;
     _overrideStartOffset = null;
     if (changes == _ChangeDescription.resized)
       _resetCache();

packages/flutter/lib/src/widgets/pageable_list.dart

@@ -165,7 +165,7 @@ class PageableListState<T extends PageableList> extends ScrollableState<T> {
   Widget buildContent(BuildContext context) {
     return new PageViewport(
       itemsWrap: config.itemsWrap,
-      scrollDirection: config.scrollDirection,
+      mainAxis: config.scrollDirection,
       scrollAnchor: config.scrollAnchor,
       startOffset: scrollOffset,
       overlayPainter: config.scrollableListPainter,
@@ -226,17 +226,17 @@ class PageableListState<T extends PageableList> extends ScrollableState<T> {
 class PageViewport extends VirtualViewportFromIterable {
   PageViewport({
     this.startOffset: 0.0,
-    this.scrollDirection: Axis.vertical,
+    this.mainAxis: Axis.vertical,
     this.scrollAnchor: ViewportAnchor.start,
     this.itemsWrap: false,
     this.overlayPainter,
     this.children
   }) {
-    assert(scrollDirection != null);
+    assert(mainAxis != null);
   }
 
   final double startOffset;
-  final Axis scrollDirection;
+  final Axis mainAxis;
   final ViewportAnchor scrollAnchor;
   final bool itemsWrap;
   final Painter overlayPainter;
@@ -274,7 +274,7 @@ class _PageViewportElement extends VirtualViewportElement {
 
   void updateRenderObject(PageViewport oldWidget) {
     renderObject
-      ..scrollDirection = widget.scrollDirection
+      ..mainAxis = widget.mainAxis
       ..overlayPainter = widget.overlayPainter;
     super.updateRenderObject(oldWidget);
   }
@@ -285,7 +285,7 @@ class _PageViewportElement extends VirtualViewportElement {
     final Size containerSize = renderObject.size;
 
     Size materializedContentSize;
-    switch (widget.scrollDirection) {
+    switch (widget.mainAxis) {
       case Axis.vertical:
         materializedContentSize = new Size(containerSize.width, _materializedChildCount * containerSize.height);
         break;
@@ -299,7 +299,7 @@ class _PageViewportElement extends VirtualViewportElement {
   void layout(BoxConstraints constraints) {
     final int length = renderObject.virtualChildCount;
 
-    switch (widget.scrollDirection) {
+    switch (widget.mainAxis) {
       case Axis.vertical:
         _containerExtent = renderObject.size.height;
         break;

packages/flutter/lib/src/widgets/scrollable.dart

@@ -8,7 +8,7 @@ import 'dart:ui' as ui show window;
 
 import 'package:newton/newton.dart';
 import 'package:flutter/gestures.dart';
-import 'package:flutter/rendering.dart' show HasScrollDirection;
+import 'package:flutter/rendering.dart' show HasMainAxis;
 
 import 'basic.dart';
 import 'framework.dart';
@@ -657,7 +657,7 @@ class _ScrollableViewportState extends ScrollableState<ScrollableViewport> {
   Widget buildContent(BuildContext context) {
     return new Viewport(
       paintOffset: scrollOffsetToPixelDelta(scrollOffset),
-      scrollDirection: config.scrollDirection,
+      mainAxis: config.scrollDirection,
       scrollAnchor: config.scrollAnchor,
       onPaintOffsetUpdateNeeded: _handlePaintOffsetUpdateNeeded,
       child: config.child
@@ -692,7 +692,7 @@ class Block extends StatelessComponent {
   final Key scrollableKey;
 
   Widget build(BuildContext context) {
-    Widget contents = new BlockBody(children: children, direction: scrollDirection);
+    Widget contents = new BlockBody(children: children, mainAxis: scrollDirection);
     if (padding != null)
       contents = new Padding(padding: padding, child: contents);
     return new ScrollableViewport(
@@ -709,15 +709,15 @@ class Block extends StatelessComponent {
 abstract class ScrollableListPainter extends Painter {
   void attach(RenderObject renderObject) {
     assert(renderObject is RenderBox);
-    assert(renderObject is HasScrollDirection);
+    assert(renderObject is HasMainAxis);
     super.attach(renderObject);
   }
 
   RenderBox get renderObject => super.renderObject;
 
   Axis get scrollDirection {
-    HasScrollDirection scrollable = renderObject as dynamic;
-    return scrollable?.scrollDirection;
+    HasMainAxis scrollable = renderObject as dynamic;
+    return scrollable?.mainAxis;
   }
 
   Size get viewportSize => renderObject.size;

packages/flutter/lib/src/widgets/scrollable_grid.dart

@@ -77,8 +77,8 @@ class GridViewport extends VirtualViewportFromIterable {
   final ExtentsChangedCallback onExtentsChanged;
   final Iterable<Widget> children;
 
-  // TODO(abarth): Support horizontal scrolling;
-  Axis get scrollDirection => Axis.vertical;
+  // TODO(abarth): Support horizontal grids.
+  Axis get mainAxis => Axis.vertical;
 
   RenderGrid createRenderObject(BuildContext context) => new RenderGrid(delegate: delegate);
 

packages/flutter/lib/src/widgets/scrollable_list.dart

@@ -78,7 +78,7 @@ class _ScrollableListState extends ScrollableState<ScrollableList> {
     return new ListViewport(
       onExtentsChanged: _handleExtentsChanged,
       scrollOffset: scrollOffset,
-      scrollDirection: config.scrollDirection,
+      mainAxis: config.scrollDirection,
       scrollAnchor: config.scrollAnchor,
       itemExtent: config.itemExtent,
       itemsWrap: config.itemsWrap,
@@ -93,20 +93,20 @@ class _VirtualListViewport extends VirtualViewport {
   _VirtualListViewport(
     this.onExtentsChanged,
     this.scrollOffset,
-    this.scrollDirection,
+    this.mainAxis,
     this.scrollAnchor,
     this.itemExtent,
     this.itemsWrap,
     this.padding,
     this.overlayPainter
   ) {
-    assert(scrollDirection != null);
+    assert(mainAxis != null);
     assert(itemExtent != null);
   }
 
   final ExtentsChangedCallback onExtentsChanged;
   final double scrollOffset;
-  final Axis scrollDirection;
+  final Axis mainAxis;
   final ViewportAnchor scrollAnchor;
   final double itemExtent;
   final bool itemsWrap;
@@ -114,7 +114,7 @@ class _VirtualListViewport extends VirtualViewport {
   final Painter overlayPainter;
 
   double get _leadingPadding {
-    switch (scrollDirection) {
+    switch (mainAxis) {
       case Axis.vertical:
         switch (scrollAnchor) {
           case ViewportAnchor.start:
@@ -166,7 +166,7 @@ class _VirtualListViewportElement extends VirtualViewportElement {
 
   void updateRenderObject(_VirtualListViewport oldWidget) {
     renderObject
-      ..scrollDirection = widget.scrollDirection
+      ..mainAxis = widget.mainAxis
       ..scrollAnchor = widget.scrollAnchor
       ..itemExtent = widget.itemExtent
       ..padding = widget.padding
@@ -186,7 +186,7 @@ class _VirtualListViewportElement extends VirtualViewportElement {
     double containerExtent;
     double contentExtent;
 
-    switch (widget.scrollDirection) {
+    switch (widget.mainAxis) {
       case Axis.vertical:
         containerExtent = containerSize.height;
         contentExtent = length == null ? double.INFINITY : widget.itemExtent * length + padding.vertical;
@@ -222,7 +222,7 @@ class _VirtualListViewportElement extends VirtualViewportElement {
     }
 
     Size materializedContentSize;
-    switch (widget.scrollDirection) {
+    switch (widget.mainAxis) {
       case Axis.vertical:
         materializedContentSize = new Size(containerSize.width, _materializedChildCount * itemExtent);
         break;
@@ -246,7 +246,7 @@ class ListViewport extends _VirtualListViewport with VirtualViewportFromIterable
   ListViewport({
     ExtentsChangedCallback onExtentsChanged,
     double scrollOffset: 0.0,
-    Axis scrollDirection: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     ViewportAnchor scrollAnchor: ViewportAnchor.start,
     double itemExtent,
     bool itemsWrap: false,
@@ -256,7 +256,7 @@ class ListViewport extends _VirtualListViewport with VirtualViewportFromIterable
   }) : super(
     onExtentsChanged,
     scrollOffset,
-    scrollDirection,
+    mainAxis,
     scrollAnchor,
     itemExtent,
     itemsWrap,
@@ -341,7 +341,7 @@ class _ScrollableLazyListState extends ScrollableState<ScrollableLazyList> {
     return new LazyListViewport(
       onExtentsChanged: _handleExtentsChanged,
       scrollOffset: scrollOffset,
-      scrollDirection: config.scrollDirection,
+      mainAxis: config.scrollDirection,
       scrollAnchor: config.scrollAnchor,
       itemExtent: config.itemExtent,
       itemCount: config.itemCount,
@@ -356,7 +356,7 @@ class LazyListViewport extends _VirtualListViewport with VirtualViewportFromBuil
   LazyListViewport({
     ExtentsChangedCallback onExtentsChanged,
     double scrollOffset: 0.0,
-    Axis scrollDirection: Axis.vertical,
+    Axis mainAxis: Axis.vertical,
     ViewportAnchor scrollAnchor: ViewportAnchor.start,
     double itemExtent,
     EdgeDims padding,
@@ -366,7 +366,7 @@ class LazyListViewport extends _VirtualListViewport with VirtualViewportFromBuil
   }) : super(
     onExtentsChanged,
     scrollOffset,
-    scrollDirection,
+    mainAxis,
     scrollAnchor,
     itemExtent,
     false, // Don't support wrapping yet.

packages/flutter/lib/src/widgets/virtual_viewport.dart

@@ -62,7 +62,7 @@ abstract class VirtualViewportElement extends RenderObjectElement {
   /// Returns a two-dimensional representation of the scroll offset, accounting
   /// for the scroll direction and scroll anchor.
   Offset scrollOffsetToPixelDelta(double scrollOffset) {
-    switch (renderObject.scrollDirection) {
+    switch (renderObject.mainAxis) {
       case Axis.horizontal:
         return new Offset(scrollOffsetToPixelOffset(scrollOffset), 0.0);
       case Axis.vertical:

packages/flutter/test/widget/aspect_ratio_test.dart

@@ -40,7 +40,7 @@ void main() {
       tester.pumpWidget(
         new Center(
           child: new Viewport(
-            scrollDirection: Axis.horizontal,
+            mainAxis: Axis.horizontal,
             child: new AspectRatio(
               aspectRatio: 2.0,
               child: new Container(