Rather than not drawing, which will miss some imported elements that
should be visible due to the line width, we draw a zero-length line that
appears as a point.
Currently this lives behind the advanced config flag `UseClipper2`.
Enabling this flag will route all Clipper-based calls through the
Clipper2 library instead of the older Clipper. The changes should be
mostly transparent.
Of note, Clipper2 does not utilize the `STRICTLY_SIMPLE` flag because
clipper1 did not actually guarantee a strictly simple polygon.
Currently we ignore this flag but we may decide to run strictly-simple
operations through a second NULL union to simplify the results as much
as possible.
Additionally, the inflation options are slightly different. We cannot
choose the fallback miter. The fallback miter is always square. This
only affects the CHAMFER_ACUTE_CORNERS option in inflate, which does not
appear to be used.
Lastly, we currently utilize the 64-bit integer coordinates for
calculations. This appears to still be faster than 32-bit calculations
in Clipper1 on a modern x86 system. This may not be the case for older
systems, particularly 32-bit systems.
1) The highest priority zone that a via/pad collides with "owns" its
connectivity state. Once set, lower priority zones cannot change it --
and in fact, if they would have connected to it are forced not to.
2) The connectivity state goes with the zone fill state, and therefore
must be saved in the file.
3) Display of remove-unconnected's pads is no longer done in GetViewLOD()
(which isn't called for selected items), and is instead done in PCB_PAINTER.
This allows us to draw the full pad in outline mode when a via/pad is
selected which would otherwise only show the hole.
4) Note that in some cases this will still generate DRC errors -- in
particular when a via nearly collides with a higher priority zone it
won't get "owned" by that zone and may therefore have insufficient
clearance if said zone concludes it's unconnected and a subsequent
(lower priority) zone connects to it (causing it to now become flashed).
Fixes https://gitlab.com/kicad/code/kicad/issues/11299
It might make sense to do that with board and/or schematic items for
hit-testing or something, but it definitely doesn't make any sense for
the drawing sheet border.
Also, when reading in items with a transparent fill, treat them as
unfilled (otherwise we get filled with layer colour in at least PCBNew).