gEDA-user: Hidden rectangle in PCB causing headaches

["joe tarantino" <joeft@xxxxxxxxxxxxx>]

We've just completed a board which had us scratching our heads when we
ran the DRC.  We also found problems in the gerber output.

I trimmed the file down to a very simple example (1 part, 1 via, 1
trace, 1 rectangle).  The culprit is the rectangle.  If you
place a rectangle under a pad for example, and the rectangle is smaller
than the "cleared" area around the pad, none of the rectangle is
drawn.  This is ok.  However, the DRC complains about "Pad
with insufficient clearance inside polygon".  It also generates
gerber output with a polygon in it, but with what looks like an
incorrect D code.  One of the gerber viewers we use (Viewmaster)
also flags a DRC error.  You can actually select it in the gerber
viewer if you know where to look, but it is invisible.  (I don't
know how it can track an invisible feature - the gerber output is
attached so maybe someone more knowledgeable can figure it out).

Getting rid of this error was difficult.  Since you can not see
the feature (even when drawing with fill turned off), it is very hard
to edit or remove it in PCB.  You can remove it in the text file,
but on a large board it may take a while to find it.  The DRC
report isn't helpful, since it reports a co-ordinate near where the
violation is detected, but this is not always enough when several
features overlap.

Several possibilities for fixing this include:
1) Allow for separate display of different feature types on the same
layer.  For example, allow viewing of rectangles or lines on the
top layer without the pads on the top layer turned on *and* show all
the things that would have been covered by the pad clearances.
2) Have the DRC show all co-ordinates associated the features which cause the error, rather than just one point nearby.
3) If a feature such as this rectangle is going to be completely
occluded, it should be completely removed from the gerber output.

Any other suggestions?

Excerpt from PCB file and gerber output attached.

Thanks,

Joe

Attachment: DRCtest_excerpt
Description: Binary data

Attachment: DRCtest.output_front.gbr
Description: Binary data

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