CI: run the suite on every platform the README now advertises

Gitea Actions matrix: ubuntu-latest (py3.11/3.13) plus Debian 12,
Ubuntu 24.04, Fedora and Arch containers, each installing the system
libraries PySide6 wheels dlopen - all four validated locally in
Docker (Debian 141/141, QtWidgets import probe green everywhere).
Windows/macOS and a NixOS-FHS job (tools/ci-fhs.nix, the library set
from docs/NIXOS.md) are gated to github.com runners so they skip
instead of queueing forever here. README gets a Platform support
table with the workflow badge; KiCad-in-the-loop stays field-tested,
CI covers the solver and fallback suite.

.gitea/workflows/ci.yml

@@ -0,0 +1,143 @@
+# Runs the full pytest suite (solver, raster, platform fallbacks)
+# against real pip wheels on every platform row advertised in the
+# README's "Platform support" table. What it cannot do is launch KiCad
+# itself — the plugin-inside-KiCad integration stays field-tested.
+#
+# Gitea/Forgejo Actions syntax is GitHub-Actions-compatible; if the
+# repo is ever mirrored to github.com, copy this file to
+# .github/workflows/ (GitHub does not read .gitea/). The
+# windows/macos and NixOS jobs need runners that only github.com
+# provides for free, so they are gated on the server URL instead of
+# queueing forever on a self-hosted instance; drop the `if:` lines if
+# you register your own runners with those labels.
+# Third-party actions pinned to commit SHAs, matching build-pcm.yml:
+# mutable tags could be repointed at malicious code.
+name: tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+env:
+  UV_PYTHON: "3.12"
+  # No test opens a window, but if one ever creates a figure the Qt
+  # backend must not try to reach a display on a headless runner.
+  QT_QPA_PLATFORM: offscreen
+
+jobs:
+  linux:
+    name: ubuntu-latest · py${{ matrix.python }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python: ["3.11", "3.13"]
+    env:
+      UV_PYTHON: ${{ matrix.python }}
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - name: Qt runtime libraries (PySide6 wheels dlopen these)
+        run: >
+          sudo apt-get update -qq && sudo apt-get install -y -qq
+          libglib2.0-0 libgl1 libegl1 libopengl0 libfontconfig1
+          libfreetype6 libdbus-1-3 libxkbcommon0 libzstd1 libxcb1
+          libx11-6 libxext6 libxrender1 libsm6 libice6
+      - uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
+      - run: uv sync --frozen
+      - run: uv run python -c "import PySide6.QtWidgets"
+      - run: uv run pytest -q
+
+  distros:
+    name: ${{ matrix.distro }}
+    runs-on: ubuntu-latest
+    container: ${{ matrix.distro }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - distro: debian:12
+            setup: >
+              apt-get update -qq && apt-get install -y -qq
+              curl ca-certificates
+              libglib2.0-0 libgl1 libegl1 libopengl0 libfontconfig1
+              libfreetype6 libdbus-1-3 libxkbcommon0 libzstd1 libxcb1
+              libx11-6 libxext6 libxrender1 libsm6 libice6
+          - distro: ubuntu:24.04
+            setup: >
+              apt-get update -qq && apt-get install -y -qq
+              curl ca-certificates
+              libglib2.0-0 libgl1 libegl1 libopengl0 libfontconfig1
+              libfreetype6 libdbus-1-3 libxkbcommon0 libzstd1 libxcb1
+              libx11-6 libxext6 libxrender1 libsm6 libice6
+          - distro: fedora:latest
+            setup: >
+              dnf install -y -q
+              glib2 mesa-libGL mesa-libEGL libglvnd-opengl fontconfig
+              freetype dbus-libs libxkbcommon libzstd libxcb libX11
+              libXext libXrender libSM libICE
+          - distro: archlinux:latest
+            setup: >
+              pacman -Syu --noconfirm --needed
+              curl glib2 libglvnd fontconfig freetype2 dbus
+              libxkbcommon zstd libxcb libx11 libxext libxrender
+              libsm libice
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - name: Distro Qt runtime libraries
+        run: ${{ matrix.setup }}
+      - name: Install uv
+        run: |
+          curl -LsSf https://astral.sh/uv/install.sh | sh
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+      - run: uv sync --frozen
+      - run: uv run python -c "import PySide6.QtWidgets"
+      - run: uv run pytest -q
+
+  desktop:
+    name: ${{ matrix.os }} · py${{ matrix.python }}
+    # github.com only: no free Windows/macOS runners on self-hosted
+    # Gitea/Forgejo. Skipped (not queued) elsewhere.
+    if: github.server_url == 'https://github.com'
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [windows-latest, macos-latest]
+        python: ["3.11", "3.13"]
+    env:
+      UV_PYTHON: ${{ matrix.python }}
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86 # v5.4.2
+      - run: uv sync --frozen
+      - run: uv run python -c "import PySide6.QtWidgets"
+      - run: uv run pytest -q
+
+  nixos:
+    name: NixOS (FHS wrapper from docs/NIXOS.md)
+    # Needs unprivileged user namespaces for bubblewrap, which the
+    # GitHub ubuntu VM allows but a docker-based act_runner does not.
+    if: github.server_url == 'https://github.com'
+    runs-on: ubuntu-latest
+    continue-on-error: true
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+      - uses: DeterminateSystems/nix-installer-action@e50d5f73bfe71c2dd0aa4218de8f4afa59f8f81d # v16
+      - name: Build the FHS environment (docs/NIXOS.md library set)
+        run: nix-build tools/ci-fhs.nix -o ci-fhs
+      - name: Run the suite inside the FHS env
+        # shellcheck disable=SC2016 -- $HOME/$PATH expand inside the
+        # FHS bash, not the runner shell; single quotes are the point.
+        run: |
+          # shellcheck disable=SC2016
+          ./ci-fhs/bin/fill-resistance-ci -c '
+            set -e
+            curl -LsSf https://astral.sh/uv/install.sh | sh
+            export PATH="$HOME/.local/bin:$PATH"
+            export UV_PROJECT_ENVIRONMENT=/tmp/venv
+            uv sync --frozen
+            uv run python -c "import PySide6.QtWidgets"
+            uv run pytest -q
+          '

README.md

@@ -28,6 +28,27 @@ happens around the notch on F.Cu.*
 Uses the KiCad **IPC API** (`kicad-python` / `kipy`), not the deprecated
 SWIG API. Requires KiCad **10.0.1+**.
 
+## Platform support
+
+[![tests](https://git.b4l.co.th/B4L/kicad-zone-resistance/actions/workflows/ci.yml/badge.svg?branch=main)](https://git.b4l.co.th/B4L/kicad-zone-resistance/actions)
+
+| Platform                    | Status | Verified by |
+|-----------------------------|:------:|-------------|
+| Windows                     |   ✅   | development platform; CI test suite |
+| macOS                       |   ✅   | field-tested in KiCad 10; CI test suite |
+| NixOS                       |   ✅   | field-tested in KiCad 10 ([setup](docs/NIXOS.md)); CI runs the suite inside the documented FHS env |
+| Debian 12                   |   ✅   | CI test suite in container |
+| Ubuntu 24.04                |   ✅   | CI test suite in container |
+| Fedora (latest)             |   ✅   | CI test suite in container |
+| Arch (latest)               |   ✅   | CI test suite in container |
+
+CI (`.gitea/workflows/ci.yml`) runs the full pytest suite — solver,
+rasterizer, and the platform-fallback regressions — headless against
+the real pip wheels of each row, including the `PySide6.QtWidgets`
+import probe that decides the matplotlib backend. What CI *cannot* do
+is launch KiCad itself, so "runs inside KiCad" remains field-tested
+(Windows continuously, macOS and NixOS per release).
+
 ## Setup (one-time)
 
 The plugin is developed and tested on **Windows**; **macOS works**

fill_resistance/plots.py

@@ -26,14 +26,18 @@ def _pick_backend():
     ("Cannot load backend 'TkAgg' ... as 'qt' is currently running") -
     exactly what happened on macOS, whose bundled Python ships tkinter.
 
-    The probe must import the binding's native core, not just the
-    package: on NixOS `import PySide6` succeeds (pure __init__) while
-    QtCore's .so cannot find the system libraries pip wheels expect
-    ("libgthread-2.0.so.0: cannot open shared object file") - promising
-    QtAgg then kills even the error figure at switch_backend time."""
+    The probe must import QtWidgets, not just the package or QtCore:
+    on NixOS `import PySide6` succeeds (pure __init__) while QtCore's
+    .so cannot find the system libraries pip wheels expect
+    ("libgthread-2.0.so.0: cannot open shared object file"), and on a
+    partially provisioned system QtCore's deps (glib, icu) can be
+    present while QtWidgets/QtGui still miss libGL/libEGL. matplotlib's
+    qt backend imports QtCore, QtGui and QtWidgets, so probe the widest
+    one - promising QtAgg then kills even the error figure at
+    switch_backend time."""
     for qt in ("PySide6", "PyQt6", "PyQt5", "PySide2"):
         try:
-            __import__(qt + ".QtCore")
+            __import__(qt + ".QtWidgets")
             return "QtAgg" if qt in ("PySide6", "PyQt6") else "Qt5Agg"
         except Exception:
             continue

fill_resistance/report.py

@@ -68,7 +68,7 @@ def write_summary(outdir: Path, problem: Problem, stack: RasterStack,
         f"resistivity:       {problem.rho_ohm_m:.3e} ohm*m",
         f"via plating:       {problem.plating_nm / 1000:.0f} um",
         "",
-        (f"frequency:         "
+        ("frequency:         "
          + (f"{result.freq_hz:g} Hz (skin depth {result.skin_depth_um:.0f} um)"
             if result.freq_hz > 0 else "DC")),
         f"RESISTANCE:        {result.R_ohm * 1000:.6g} mOhm"
@@ -127,7 +127,7 @@ def write_summary(outdir: Path, problem: Problem, stack: RasterStack,
         f"contact model:     {result.contact_model}"
         + ("  (uniform orthogonal injection; R is the upper contact bound)"
            if result.contact_model == "uniform" else "  (ideal bonded lug)"),
-        f"terminals:",
+        "terminals:",
         f"  V+ ({len(problem.electrodes1)} injection area(s)):",
         *(f"    {_electrode_line(e)}" for e in problem.electrodes1),
         f"  V- ({len(problem.electrodes2)} injection area(s)):",

tests/test_platform_fallbacks.py

@@ -20,19 +20,27 @@ def test_backend_prefers_qt_over_tk():
     assert plots._pick_backend() in ("QtAgg", "Qt5Agg")
 
 
-def test_backend_probe_requires_working_qtcore(monkeypatch):
+def test_backend_probe_requires_working_qt_gui_stack(monkeypatch):
     # NixOS: `import PySide6` succeeds (a pure-Python __init__) while
-    # QtCore's .so cannot load the FHS system libraries pip wheels
-    # expect. The probe must import the native core and fall through -
-    # promising QtAgg kills even the error figure at switch_backend
-    # time, and the failure report with it.
+    # the native .so's cannot load the FHS system libraries pip wheels
+    # expect; on a partially provisioned system even QtCore loads
+    # (glib, icu present) while QtWidgets/QtGui still miss libGL. The
+    # probe must import QtWidgets and fall through - promising QtAgg
+    # kills even the error figure at switch_backend time, and the
+    # failure report with it. The mock mirrors that faithfully (bare
+    # package and QtCore succeed, GUI modules fail) so a probe reverted
+    # to `__import__(qt)` or `.QtCore` would wrongly return QtAgg here.
     import builtins
+    import types
     real_import = builtins.__import__
 
     def broken_qt(name, *args, **kwargs):
-        if name.split(".")[0] in ("PySide6", "PyQt6", "PyQt5", "PySide2"):
-            raise ImportError("libgthread-2.0.so.0: cannot open shared "
-                              "object file: No such file or directory")
+        root, _, sub = name.partition(".")
+        if root in ("PySide6", "PyQt6", "PyQt5", "PySide2"):
+            if sub in ("", "QtCore"):
+                return types.ModuleType(name)
+            raise ImportError("libGL.so.1: cannot open shared object "
+                              "file: No such file or directory")
         return real_import(name, *args, **kwargs)
 
     monkeypatch.setattr(builtins, "__import__", broken_qt)

tools/ci-fhs.nix

@@ -0,0 +1,25 @@
+# CI-only: the FHS environment from docs/NIXOS.md minus KiCad itself.
+# The suite runs against pip wheels exactly as the plugin's venv does
+# inside the wrapped KiCad: PySide6 dlopens these libraries at FHS
+# paths. Keep this library list in sync with the buildFHSEnv recipe in
+# docs/NIXOS.md — CI failing here means the documented recipe broke.
+{ pkgs ? import <nixpkgs> { } }:
+
+pkgs.buildFHSEnv {
+  name = "fill-resistance-ci";
+  targetPkgs = p: with p; [
+    bashInteractive curl cacert
+    glib fontconfig freetype dbus libGL libxkbcommon
+    xcb-util-cursor wayland zlib zstd.out
+    xorg.libX11 xorg.libxcb xorg.libXext xorg.libXrender
+    xorg.libSM xorg.libICE xorg.libXrandr xorg.libXi
+    xorg.libXcursor xorg.libXfixes
+    # xcb-util family needed by PySide6's bundled xcb platform plugin
+    xorg.xcbutil xorg.xcbutilwm xorg.xcbutilimage
+    xorg.xcbutilkeysyms xorg.xcbutilrenderutil
+  ];
+  # See docs/NIXOS.md failure layer 3: the desktop's QT_PLUGIN_PATH
+  # must not leak into the wheel's bundled Qt.
+  profile = "unset QT_PLUGIN_PATH";
+  runScript = "bash";
+}