Graphical polygons can be added to the edge cuts layer -> Creates problems with filled zones

[Rene Poeschl]

Right now it is possible to add graphical polygons on the edge cuts layer. If a user assumes this can be used to draw the board outline then they are in trouble.
More details see this forum topic: https://forum.kicad.info/t/copper-pour-doesnt-fill/12858

The user bobc suggested the following solutions in that forum topic:

>There is a trade-off between “being a nanny” and “giving the user too much rope”. KiCad sometimes strays too far to one side or the other. You may have a case where 1) the polygon needs to have different processing depending on layer; 2) KiCad should prevent polygons on certain layers.

I assume there have been plans to make polygons more powerful and have them useful on all layers.
With the current featureset i lean towards proposed solution 2. I do not see a use for graphical polygons on the edge cut layer. I would suggest to have a warning pop up that tells the user that the graphical polygon tool is not intended to be used for drawing the board outline. (That way it can still be used as a workaround if there ever is a usecase found for it. But normal users will be warned that they have the wrong tool.)

[Seth Hillbrand (sethh)]

I think if the user decides to utilize a polygon on the edge cuts layer, we should simply treat it as a closed polyline. That is how is is displayed on the screen and there doesn't seem to be a downside.

[Wayne Stambaugh (stambaughw)]

@Seth, wouldn't this change how any existing board with polygons on the edge cut layer are interpreted? I'm not sure this is a good idea as it could cause some unexpected consequences. I agree that the polygons should be interpreted as a closed polyline but that should have been done from the beginning.

[Seth Hillbrand (sethh)]

Right now, any board with a polygon on the edge cuts layer is broken. Fills don't work, the 3d-viewer doesn't see the outline and the gerber output is a filled polygon.

I'm happy to just ban the layer to new polygons but the polyline solution seemed more useful.

[Wayne Stambaugh (stambaughw)]

I guess the question is would a user do this on purpose? If so, than changing this would change the gerber files which is not a good thing. If not, then converting the polygon to a closed polyline seems like a reasonable solution. I honestly do not see the former being the intent of the user but you never know. Anyone else have an opinion on this?

[Jeff Young (jeyjey)]

I've seen quite a few reports of this on the forum. So folks are doing it -- probably just because they picked the wrong tool rather than for any "real" reason.

[Wayne Stambaugh (stambaughw)]

I'm fine with making this change and seeing what happens. We can always back it out later if there are issues.

[eelik (eelik)]

Here's the latest discussion in the forum: https://forum.kicad.info/t/problem-creating-fill-zones-and-board-outline/13984

A very quick solution without making drastic changes to code or changing existing would be to make DRC catch it. Right now "graphic polygons" seem to be handled like segments. Polygons aren't handled at all. DRC could just take existence of both as an error and give a corresponding warning (not just "Board outline does not form a closed polygon").

[eelik (eelik)]

"changing existing" -> "changing existing functionality"
"Polygons aren't handled at all" -> "Zones aren't handled at all"

This refers to the current (8757fcf67) code. Check for continuity of Edge.Cuts segments have already been added lately.

[KiCad Janitor (kicad-janitor)]

Fixed in revision 1858b7dca7a6b38d52a6360783d7c4cd02e33c38
https://git.launchpad.net/kicad/patch/?id=1858b7dca7a6b38d52a6360783d7c4cd02e33c38