Polygon-line intersection error

[dkogan55]

Hi. I found a bug in the code that clears a buffer around lines that are routed through polygons. In an edge case where two lines meet at exactly the same point, the algorithms can fail and compute the polygon improperly.

The attached pcb demonstrates the problem. There are two lines and a rectangle. If either of the two lines is moved over even by a mil, or if the order of the lines is reversed, the problem goes away.

I've traced the issue down to the
M_POLYAREA_Collect() call in poly_Boolean_free(). I suspect that the calls to M_POLYAREA_label() directly above that are creating incorrect labels that, in turn, cause M_POLYAREA_Collect() to produce erroneous polygons, but I'm not sure.

[DJ Delorie (djdelorie)]

Seems to work now. We've done some work on the polygon code, could you check it again and see if it works for you too?

[dkogan55 (dkogan55)]

I confirm that it works with the newest builds, but was broken in 20091103. A bisection tells me that the fix happened in one of

7fb579af50cd41e1bb50a12af4d59003f90f0bbb
dc9052b1b4976c3dee3e39290b03ed8da94a7a63
1099c473dc24b8c1567261235ae3f4916b47cfc7
64c875b0662e285dc101e7b2a0392a4c743c8700
d5d894d977e610308d6ec36a3670cf3c94a8b015

which are all Peter Clifton's polygon patches from 11 Nov 2009. Thanks to Peter for fixing this. Closing bug.

[Traumflug (mah-jump-ing)]

Marking as "closed" as per reporters request.

[Chad Parker (parker-charles)]

Fixed long ago...