[GRASS5] [bug #1182] (grass) grass5.1 d.vect doesn't show all lines falling within zoomed display

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this bug's URL: http://intevation.de/rt/webrt?serial_num=1182
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Subject: grass5.1 d.vect  doesn't show all lines falling within zoomed display

Apparently if a 2D vector has at least one of its end points within the active
display area, whole visible subsegment is shown successfully.

When a subsegment just intersects the display area and both its end points are
outside, either the line is not drawn at all, or is drawn with wrong colour.

This appears with Grass 5.1 d.vect from CVS of about a week ago.

This shows symptoms of classical computer graphics vector visibility problem,
and should be fairly easy to fix by following algorithms in basic computer
graphics books.  (Unfortunately I have misplaced my reference books, and can't
fix it right away.)

Does it happen with 5.0, I have not verified. I have used 5.1's 3D vectors to
model various buildings and other constructs at a hilltop.


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