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[RFC] new connectivity algorithm - testers needed


Hi all,

I've pushed the branch [1] containing a rewrite of the pcbnew's
connectivity algorithm. By this algorithm, I mean:
- computing the ratsnest and checking if all connections are complete
- propagating net codes from the pads to the tracks/vias
- removing unconnected copper islands in zones

Compared to the old algorithm, it introduces several new
- no limitations in via/zone connections - you can have loose (stitching
vias), overlapping copper zones or zones connecting pads/vias without
direct track connections.
- items no longer loose their nets when not connected to any pad.
connecting to a new pad causes automatic net code propagation.
- the algorithm makes zero assumptions about connectivity of the items,
vias in particular. This removes another obstacle importing designs from
other tools (neither Eagle nor Altium make difference between stitching
and 'ordinary' vias).
- ratsnest can be calculated between any sort of copper items (not only
pads). This is a must-have if we want to have copper arcs or arbitrary
copper shapes in the future.
- show local ratsnest works for the GAL
- marking missing connections between overlapping objects on different
- free via placement tool

The branch also contains a bit of refactoring of the base pcbnew code:
- hidden DLISTS behind iterators. Now you can use ordinary C++11 range
based for to iterate over board's primitives. This is the first step
towards cleanin up the storage model.

As with all new stuff, there are some still some issues to sort out:
- the legacy autorouter is currently disabled, as it relies a lot on the
old connectivity algorithm's data model. We're working to migrate it to
the new one alongside porting it to the GAL canvas.
- there's no automated via stitching tool yet. I'm waiting to review
Heikki's patches for the automagic via stitcher.
- the message panel does no longer show the 'links' and 'nodes' counters
as the new ratsnest has no direct counterpart for these. Is there any
purpose for these counters other than diagnostics/debug?
- some code formatting/cleanup may still be necessary

@Heikki - once again, the sooner you'll publish your entire via
stitching code, the higher the chance you'll get it integrated in Kicad.
We can help with that.

I encourage you to check out the branch, build it and test with your
designs. In particular, if you tried zone stitching with single-pad
components, try replacing them with vias and check if the board
connectivity is correctly resolved and there are no DRC errors.

I'll send some boards demonstrating the new features soon.

Your feedback will be greatly appreciated!


[1] https://github.com/twlostow/kicad-dev/tree/tom-connectivity-apr24

PS. The final branch will also support per-net rat line visibility and
colors as a bonus ;-)

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