layout.py

# Extracts QMK `info.json` layout data from kicad pcb
# You need to have the `pcbnew` module importable (should be installed when kicad is installed)

import re, pcbnew, json
from typing import Callable
from functools import reduce

kicad7 = pcbnew.Version().startswith("7")

if kicad7:
    iu2mm = lambda iu: iu / pcbnew.PCB_IU_PER_MM
    PrimPointType = lambda *a: pcbnew.VECTOR2I(pcbnew.wxPoint(*a))
    def check_layers(fp: pcbnew.FOOTPRINT) -> list:
        return pcbnew.LSET.AllNonCuMask().Seq()
else:
    iu2mm = pcbnew.Iu2Millimeter
    PrimPointType = pcbnew.wxPoint
    def check_layers(fp: pcbnew.FOOTPRINT) -> list:
        layers = (pcbnew.LSET_PhysicalLayersMask()
            .removeLayer(pcbnew.F_SilkS).removeLayer(pcbnew.B_SilkS)
            .addLayer(pcbnew.F_CrtYd).addLayer(pcbnew.B_CrtYd).addLayer(pcbnew.Margin).addLayer(pcbnew.Edge_Cuts))
        l = fp.GetLayerSet()
        return l.RemoveLayerSet(layers).Seq()

def get_layout(fn: str, f: Callable[[pcbnew.FOOTPRINT], bool]) -> None:
    board: pcbnew.BOARD = pcbnew.LoadBoard(fn)
    switches = sorted((fp for fp in board.GetFootprints() if f(fp)), key=lambda sw: int(re.search("\\d+", sw.GetReference()).group(0)))

    def get_params(fp: pcbnew.FOOTPRINT) -> list[float]:
        deg = fp.GetOrientationDegrees()
        if deg != 0:
            deg -= 90 * round(deg / 90)     # snap to nearest 90deg
            if kicad7:
                rot = pcbnew.EDA_ANGLE(-deg * 10, pcbnew.DEGREES_T)
            else:
                rot = -deg * 10
            fp.Rotate(fp.GetCenter(), rot)
        bb = fp.GetBoundingBox(False, False)
        gis = fp.GraphicalItems()
        def get_param(layer: int) -> list[float] | None:
            gs = [g for g in gis if g.GetLayer() == layer]
            if len(gs) == 0:
                return None
            bbs = [g.GetBoundingBox() for g in gs]
            merged = reduce(lambda a, b: a.Merge(b) or a, bbs)
            if not kicad7:
                merged = merged.getWxRect()
            width = list(set(g.GetWidth() for g in gs))
            if len(width) > 1:
                raise ValueError(f"more than 1 width: {width} on layer: {pcbnew.LayerName(layer)}")
            width = width[0]
            pos = bb.GetOrigin() + PrimPointType(width / 2, width / 2)
            w, h = merged.GetWidth() - width, merged.GetHeight() - width
            return [iu2mm(i) for i in [pos.x, pos.y, w, h]]
        p = max((p for layer in check_layers(fp) if (p := get_param(layer)) != None), key=lambda p: p[2:4])
        if deg != 0:
            p += [-deg]
        return p

    params = [get_params(sw) for sw in switches]
    min_size = min(s for p in params for s in p[2:4])
    min_x, min_y = min(p[0] for p in params), min(p[1] for p in params)
    params = [[round(i / min_size, 3) for i in [(p[0] - min_x), (p[1] - min_y), p[2], p[3]]] + p[4:5] for p in params]
    def to_dict(p) -> dict[str, float]:
        d = {"x": p[0], "y": p[1]}
        if p[3] == 1:
            d["w"] = p[2]
        elif p[2] == 1:
            d["h"] = p[3]
        if len(p) == 5:
            d["r"] = p[4]
        return d
    print(json.dumps({"layouts": {"default": {"layout": [to_dict(p) for p in params]}}}))

# Example:
# `f` is a footprint filtering function to get the switches. docs for the `FOOTPRINT` type: https://docs.kicad.org/doxygen-python-6.0/classpcbnew_1_1FOOTPRINT.html
get_layout("/home/steven/gitproj/fusion/fusion.kicad_pcb", lambda sw: str(sw.GetReference()).startswith("K"))

Hi, could you share a .kicad_pcb file that works with this script? I tried it on Lily58 and corne-classic but I get a ValueError: max() arg is an empty sequence error for both. Or if you give a hint on what to modify in the script that's also appreciated.

@torjek see my comment above. Any of my projects should work with this script (see the fissure or fusion). As for modifying the script to suit other footprints, I can't say much without the exact PCB/footprints you have, although you could look at line 38 and change the layers removed on line 12 (but the keycap dimension extraction logic will probably not work if the layer used has other graphics in it).