enhance grid again

Author: fbchen

example/grid.dart

@@ -32,12 +32,12 @@ class GridExample extends StatelessWidget {
               columnCount: 8,
               itemWidth: 100,
               itemHeight: 100,
-              itemBuilder: (index) {
+              itemBuilder: (index, _, __) {
                 return Container(
                   color: colors[index % colors.length],
                 );
               },
-              itemMarginBuilder: (index) {
+              itemMarginBuilder: (index, _, __) {
                 return const EdgeInsets.only(
                   left: 10,
                   top: 10,

example/horizontal_list.dart

@@ -36,7 +36,7 @@ class HorizontalListExample extends StatelessWidget {
               columnCount: 10,
               itemWidth: wrapContent,
               itemHeight: 100,
-              itemBuilder: (index) {
+              itemBuilder: (index, _, __) {
                 return Container(
                   color: colors[index % colors.length],
                   padding: const EdgeInsets.symmetric(
@@ -45,7 +45,7 @@ class HorizontalListExample extends StatelessWidget {
                   child: Text('child $index'),
                 );
               },
-              itemMarginBuilder: (index) {
+              itemMarginBuilder: (index, _, __) {
                 return const EdgeInsets.only(
                   left: 10,
                   top: 10,

example/staggered_grid.dart

@@ -50,14 +50,14 @@ class StaggeredGridExample extends StatelessWidget {
               top: parent.top,
               itemCount: 50,
               columnCount: columnCount,
-              itemBuilder: (index) {
+              itemBuilder: (index, _, __) {
                 return Container(
                   color: colors[index % colors.length],
                   alignment: Alignment.center,
                   child: Text('$index'),
                 );
               },
-              itemSizeBuilder: (index) {
+              itemSizeBuilder: (index, _, __) {
                 if (index == 0) {
                   return const Size(
                       smallestSize * columnCount + 35, smallestSize);
@@ -95,7 +95,7 @@ class StaggeredGridExample extends StatelessWidget {
                 }
                 return 1;
               },
-              itemMarginBuilder: (index) {
+              itemMarginBuilder: (index, _, __) {
                 return const EdgeInsets.only(
                   left: 5,
                   top: 5,

example/vertical_list.dart

@@ -34,7 +34,7 @@ class VerticalListExample extends StatelessWidget {
               ),
               itemCount: 20,
               columnCount: 1,
-              itemBuilder: (index) {
+              itemBuilder: (index, _, __) {
                 return Container(
                   color: colors[index % colors.length],
                   padding: const EdgeInsets.symmetric(
@@ -43,10 +43,10 @@ class VerticalListExample extends StatelessWidget {
                   child: Text('child $index'),
                 );
               },
-              itemSizeBuilder: (index) {
+              itemSizeBuilder: (index, _, __) {
                 return const Size(100, wrapContent);
               },
-              itemMarginBuilder: (index) {
+              itemMarginBuilder: (index, _, __) {
                 return const EdgeInsets.only(
                   left: 10,
                   top: 10,

lib/src/constraint_layout.dart

@@ -111,9 +111,11 @@ List<Widget> constraintGrid({
   required int columnCount,
   double? itemWidth,
   double? itemHeight,
-  Size Function(int index)? itemSizeBuilder,
-  required Widget Function(int index) itemBuilder,
-  EdgeInsets Function(int index)? itemMarginBuilder,
+  Size Function(int index, int rowIndex, int columnIndex)? itemSizeBuilder,
+  required Widget Function(int index, int rowIndex, int columnIndex)
+      itemBuilder,
+  EdgeInsets Function(int index, int rowIndex, int columnIndex)?
+      itemMarginBuilder,
   int Function(int index)? itemSpanBuilder,
   EdgeInsets margin = EdgeInsets.zero,
   CLVisibility visibility = visible,
@@ -154,12 +156,13 @@ List<Widget> constraintGrid({
     ConstraintId itemId = ConstraintId(id.id + '_grid_item_$i');
     allChildIds.add(itemId);
 
-    EdgeInsets childMargin = itemMarginBuilder?.call(i) ?? EdgeInsets.zero;
     int itemSpan = itemSpanBuilder?.call(i) ?? 1;
     assert(itemSpan >= 1 && itemSpan <= columnCount);
     currentRowUsedSpanCount += itemSpan;
     totalUsedSpanCount += itemSpan;
 
+    late EdgeInsets childMargin;
+
     /// New row start
     if (currentRowUsedSpanCount > columnCount) {
       currentRowIndex++;
@@ -180,7 +183,14 @@ List<Widget> constraintGrid({
       /// First column
       leftAnchor = left;
       leftChildIds.add(itemId);
-      childMargin = childMargin.add(leftMargin) as EdgeInsets;
+      childMargin = (itemMarginBuilder?.call(
+                  i, currentRowIndex, currentRowUsedSpanCount - 1) ??
+              EdgeInsets.zero)
+          .add(leftMargin) as EdgeInsets;
+    } else {
+      childMargin = itemMarginBuilder?.call(
+              i, currentRowIndex, currentRowUsedSpanCount - 1) ??
+          EdgeInsets.zero;
     }
 
     // First row
@@ -218,8 +228,10 @@ List<Widget> constraintGrid({
       }
     }
 
-    Widget widget = itemBuilder(i);
-    Size? itemSize = itemSizeBuilder?.call(i);
+    Widget widget =
+        itemBuilder(i, currentRowIndex, currentRowUsedSpanCount - 1);
+    Size? itemSize =
+        itemSizeBuilder?.call(i, currentRowIndex, currentRowUsedSpanCount - 1);
     double width = itemWidth ?? itemSize!.width;
     double height = itemHeight ?? itemSize!.height;