RE: MI Display order of objects in a table.

[Warren Vick, Europa Technologies Ltd.]

Hello Martin,

> Can someone please let me know if a solution was ever discovered to gain
> control over the display order - I can categorically state that
> changing the order of the objects in the table (on the assumption that
objects
> are drawn in the order they are listed in the table) definitely doesn't
work.

There was a pretty interesting message thread about this and many -L'ers,
including myself, were not quite right with our conclusions. Andrew Dressel
cleared things up although there are still many people who want to believe
otherwise!

Firstly, as you have found, record order (ie. rowid) has nothing to do with
it. MapInfo draws map objects/features in the order processed using the map
datas spatial index. The spatial index allows MapInfo to draw quickly when
viewing only a small part of a much larger data set. Rather than check each
and every map object to see if it's on-screen the spatial index allows
MapInfo's software products to ascertain which objects need drawing with a
fraction of the processing overhead.

The problem with MapInfo's spatial indexing is that, by observation, it has
a complicated behaviour which I, for one, would not bother trying to figure
out!

The only way to guarantee that one set of objects is drawn before another is
to put them in separate layers. However, I have found (with only occasional
exception) that if you put your objects in record (rowid) order and objects
are in close proximity, then the record order is preserved for local
drawing. I've done this where it has been necessary to put region and
overlaying polyline objects in the same layer with the polylines on top.
It's not guaranteed but is the best you can do in a single layer.

Regards,
Warren Vick
Europa Technologies Ltd, U.K.
http://www.europa-tech.com

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