Merge pull request #1938 from HansMuller/grid_layout

Added Grid row and column spacing, changed padding interpretation

Grid padding now defines the distance the overall grid is inset. The grid rowSpacing and columnSpacing attributes define the space between rows and columns respectively.

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

@@ -22,6 +22,7 @@ export 'package:flutter/rendering.dart' show
     FlexJustifyContent,
     FractionalOffsetTween,
     GridDelegate,
+    GridSpecification,
     HitTestBehavior,
     MaxTileWidthGridDelegate,
     MultiChildLayoutDelegate,
@@ -1192,6 +1193,8 @@ class FixedColumnCountGrid extends GridRenderObjectWidgetBase {
     Key key,
     List<Widget> children: _emptyWidgetList,
     this.columnCount,
+    this.columnSpacing,
+    this.rowSpacing,
     this.tileAspectRatio: 1.0,
     this.padding: EdgeDims.zero
   }) : super(key: key, children: children) {
@@ -1201,6 +1204,12 @@ class FixedColumnCountGrid extends GridRenderObjectWidgetBase {
   /// The number of columns in the grid.
   final int columnCount;
 
+  /// The horizontal distance between columns.
+  final double columnSpacing;
+
+  /// The vertical distance between rows.
+  final double rowSpacing;
+
   /// The ratio of the width to the height of each tile in the grid.
   final double tileAspectRatio;
 
@@ -1210,6 +1219,8 @@ class FixedColumnCountGrid extends GridRenderObjectWidgetBase {
   FixedColumnCountGridDelegate createDelegate() {
     return new FixedColumnCountGridDelegate(
       columnCount: columnCount,
+      columnSpacing: columnSpacing,
+      rowSpacing: rowSpacing,
       tileAspectRatio: tileAspectRatio,
       padding: padding
     );
@@ -1224,6 +1235,8 @@ class MaxTileWidthGrid extends GridRenderObjectWidgetBase {
     Key key,
     List<Widget> children: _emptyWidgetList,
     this.maxTileWidth,
+    this.columnSpacing,
+    this.rowSpacing,
     this.tileAspectRatio: 1.0,
     this.padding: EdgeDims.zero
   }) : super(key: key, children: children) {
@@ -1236,6 +1249,12 @@ class MaxTileWidthGrid extends GridRenderObjectWidgetBase {
   /// The ratio of the width to the height of each tile in the grid.
   final double tileAspectRatio;
 
+  /// The horizontal distance between columns.
+  final double columnSpacing;
+
+  /// The vertical distance between rows.
+  final double rowSpacing;
+
   /// The amount of padding to apply to each child.
   final EdgeDims padding;
 
@@ -1243,6 +1262,8 @@ class MaxTileWidthGrid extends GridRenderObjectWidgetBase {
     return new MaxTileWidthGridDelegate(
       maxTileWidth: maxTileWidth,
       tileAspectRatio: tileAspectRatio,
+      columnSpacing: columnSpacing,
+      rowSpacing: rowSpacing,
       padding: padding
     );
   }