Thermal reliefs should be removed if they result in unconnected islands

[Jon Evans]

When filling zones, if thermal relief connection is selected, the algorithm will sometimes generate thermals that go nowhere. The only way I could find to prevent this is to place a keepout where I don't want thermals to appear. It would be nice if these were automatically detected and removed as part of the fill algorithm.

https://i.imgur.com/OFxakB9.jpg

Application: pcbnew
Version: (2018-01-03 revision 0945c319f)-master, debug build
Libraries:
    wxWidgets 3.0.3
    libcurl/7.55.1 OpenSSL/1.0.2g zlib/1.2.11 libidn2/2.0.2 libpsl/0.18.0 (+libidn2/2.0.2) librtmp/2.3
Platform: Linux 4.13.0-21-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
    wxWidgets: 3.0.3 (wchar_t,wx containers,compatible with 2.8) GTK+ 2.24
    Boost: 1.62.0
    Curl: 7.55.1
    Compiler: GCC 7.2.0 with C++ ABI 1011

Build settings:
    USE_WX_GRAPHICS_CONTEXT=OFF
    USE_WX_OVERLAY=OFF
    KICAD_SCRIPTING=ON
    KICAD_SCRIPTING_MODULES=ON
    KICAD_SCRIPTING_WXPYTHON=ON
    KICAD_SCRIPTING_ACTION_MENU=OFF
    BUILD_GITHUB_PLUGIN=ON
    KICAD_USE_OCE=ON
    KICAD_SPICE=ON

[Nick Østergaard (nickoe)]

This is a recent regression, I think it came with the update of the connectivity algorithm.

[Nick Østergaard (nickoe)]

I have git bisected this and got this restult:
There are only 'skip'ped commits left to test.
The first bad commit could be any of:
941ebe376c114a115cd6b1985b38cb3de0c370d6
2831268b6098559b0ed4b81dc5a01f02f2944b44
c18b638c177bf4003aaf960d6fd30092f1f6f2d7
eed924fe45e85707a3032466c76fd2289881c325
We cannot bisect more!

I suspect it is eed924f that introduces the bug. The commit description also indicates changes was made for the thermal releif.

The commits skipped could not run.

[Nick Østergaard (nickoe)]

I am also a bit worried about this warning:

pcbnew/zone_filler.cpp: In member function ‘void ZONE_FILLER::buildUnconnectedThermalStubsPolygonList(SHAPE_POLY_SET&, const ZONE_CONTAINER*, const SHAPE_POLY_SET&, double, double) const’:
pcbnew/zone_filler.cpp:1080:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                 for( unsigned ic = 0; ic < spokes.PointCount(); ic++ )
                                       ~~~^~~~~~~~~~~~~~~~~~~~~

[Chris Pavlina (pavlina-chris)]

The warning is sloppy signedness-mixing but shouldn't reeeeally be an issue, assuming PointCount() never returns negative...

[Wayne Stambaugh (stambaughw)]

I would definitely like to see this fixed before the stable 5 release. Thermals should not be generated that do not connect to anything.

[Nick Østergaard (nickoe)]

Thank you Jon, I can confirm that it is fixed in https://git.launchpad.net/kicad/commit/?id=47b8b6dc6a503c6fe57a0fa51de15d106be492eb

[KiCad Janitor (kicad-janitor)]

Fixed in revision 47b8b6dc6a503c6fe57a0fa51de15d106be492eb
https://git.launchpad.net/kicad/patch/?id=47b8b6dc6a503c6fe57a0fa51de15d106be492eb