Use case

SliverList.builder/SliverGrid.builder/SliverFixedExtentList.builder are convenience constructors for SliverList/SliverGrid/SliverFixedExtentList with a SliverChildBuilderDelegate item delegate.

The SliverChildBuilderDelegate accepts a semanticIndexOffset argument:

SliverGrid(
  gridDelegate: _gridDelegate,
  delegate: SliverChildBuilderDelegate(
    (BuildContext context, int index) {
      return const Text('...');
    },
    childCount: 2,
    semanticIndexOffset: 2,
  ),
),

However, SliverList.builder, SliverGrid.builder, and SliverFixedExtentList.builder do not accept a semanticIndexOffset argument. If you need to provide this argument, you are forced to use the delegate pattern instead of the convenience constructor.

Proposal

• Add a semanticIndexOffset argument to SliverList.builder
• Add a semanticIndexOffset argument to SliverGrid.builder
• Add a semanticIndexOffset argument to SliverFixedExtentList.builder

For example:

SliverGrid.builder(
  gridDelegate: _gridDelegate,
  semanticIndexOffset: 2,
  itemCount: 2,
  itemBuilder: (BuildContext context, int index) {
    return const Text('...');
  },
),