Yannick,
What version of MI Pro are you using?
In the soon to be released MI Pro 6.0, the Clip Region feature has a new
option which allows the Windows Display Device to perform the Clip Region
functionality. There is a good chance that using this feature will allow
your scheme to work.
If you are using MI Pro 5.5, then the processing for Clip Region is always
an Erase Outside operation (or MapBasic Overlap() function, which is the
same under the covers). In this operation, there is a pre-processing step
to remove duplicate nodes. In your case, your zero length line segments
are comprised to 2 duplicate nodes. So, the processing throws one of them
away, which leaves a one point line. Since there is no such entity as a
one point line, the object will be discarded and ignored. Basically, you
are using bad data (a zero length line), and the operation is filtering it
out.
Selection has been and continues to be done outside the Clip Region
Processing. Select any object, regardless if it is completely inside the
clip region, completely outside the clip region, or actually cut by the
clip region, and the entire original object will be highlighted.
Derek Snyder
mapinfo Corportation
Mail List:[EMAIL PROTECTED]
From: "Leduc, Yannick" <[EMAIL PROTECTED]> on 04/19/2000
03:51 PM AST
To: "MapInfo-L (E-mail)" <[EMAIL PROTECTED]>
cc:
Subject: MI Clipping region and zero length line objects
Hi L-sters!
you will say I am splitting hair, but I came across a strange
feature in MI.
Because I need only linear object in a table for thematic purpose, I
convert
point objects to zero length line objects using : Update <my table> set obj
= CreateLine(CentroidX(obj), CentroidY(obj), CentroidX(obj),
CentroidY(obj)). I was not sure that it was going to work. It did like I
expect it to. But it does not work with zero length polylines. My goal was
to override the style with a thick line that was going to mimic a circular
symbol. Until now, everything is fine. It gets strange when I set a
clipping
region. All my zero length objects are no longer visible, inside or outside
the clipping region. They are still selectable, I can see the highlight but
cannot see them when not selected. I set the clipping region to OFF, and
they are visible again. I suppose it has to do with the way objects are
processed when they are clipped. It's a very singular object, a line with
the start and end nodes at the same coordinate.
Someone has a piece of explanation to offer?
Yannick Leduc
Minist�re des Transports
Direction de la Mauricie-Centre-du-Qu�bec
Service des inventaires et du Plan
t�l.: (819) 371-6606 #331
fax: (819) 371-6136
mailto:[EMAIL PROTECTED]
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