Changed Ranges

What you'll learn

• How to diff two trees into minimal Range values for repainting or re-analysis.

Complete example

const ranges = try old_tree.getChangedRanges(&new_tree);
defer old_tree.freeChangedRanges(ranges);
for (ranges) |r| {
    std.debug.print("changed: bytes [{d}, {d}] rows {d}..{d}\n", .{
        r.start_byte, r.end_byte, r.start_point.row, r.end_point.row,
    });
}

How it works

The comparison walks both trees in lockstep. Nodes with equal symbols, child counts, and start/end points are descended into; the first node that differs on either side contributes its range, and equal leaves contribute nothing. Identical trees therefore report zero ranges, while an insertion reports only the narrow span around the new text (e.g. bytes [4, 6] for 1 + 2 → 1 + 22).

Memory ownership

getChangedRanges allocates the result slice with the old tree's allocator; freeChangedRanges on either tree releases it (both normally share your single allocator).

API used

• Changed Ranges, Range, Tree.

Related guides

• Incremental Parsing, Editing Trees