A block measured every child's bounding box twice

[redbluevn]

foreach (var item in this.Entities)
{
    if (item.GetBoundingBox().Extent == BoundingBoxExtent.Infinite && ignoreInfinite)
    {
        continue;
    }

    box = box.Merge(item.GetBoundingBox());
}

item.GetBoundingBox() is called once to test the extent and again to merge it.

That is twice per entity at one level — but blocks nest. Insert.GetBoundingBox() calls Block.GetBoundingBox(), so a block whose children are inserts of blocks whose children are inserts costs 2^depth evaluations of the same boxes. Some of those evaluations are not cheap: Arc and Circle sample 256 points, Ellipse 100, Spline up to 256.

Measurement

An architectural drawing of 188,000 entities, warm file cache, three runs each, reading the file and computing every model-space entity's box:

before   8s   8s   8s
after    5s   5s   4s

That is whole-run wall clock including parsing a 19 MB DWG, so the share actually spent measuring boxes fell by considerably more than the 40% the total shows.

Behaviour

Unchanged. The same box is computed, once, and used for both the test and the merge.

dotnet test: 2313 passed / 17 failed — identical to master at 592d70a on this machine, as expected for a change that adds no tests and alters no results.

[DomCR]

remove the comment

[redbluevn]

Done in 965dfe1 — comment removed.