add nova-plugin: in-process cxx-qt stats plugin replacing nova-stats subprocess

nix/plugin.nix

@@ -0,0 +1,79 @@
+{
+  lib,
+  rustPlatform,
+  pkg-config,
+  qt6,
+  writeShellScript,
+  runCommand,
+}:
+let
+  # nixpkgs splits Qt tools across packages: moc/rcc/qtpaths live in qtbase,
+  # qmltyperegistrar and qmlcachegen live in qtdeclarative. qt-build-utils
+  # finds tools via `qmake -query QT_INSTALL_LIBEXECS`, which only returns
+  # qtbase paths, so those two tools are invisible. Fix: combine them into a
+  # single symlink tree and point a qmake wrapper at it.
+  qtBuildTools = runCommand "qt6-build-tools" { } ''
+    mkdir -p $out/libexec $out/bin
+    for f in ${qt6.qtbase}/libexec/* ${qt6.qtbase}/bin/*; do
+      ln -sf "$f" "$out/$(echo "$f" | grep -o 'libexec\|bin')/$(basename "$f")"
+    done
+    for tool in qmltyperegistrar qmlcachegen; do
+      src="${qt6.qtdeclarative}/libexec/$tool"
+      [ -f "$src" ] && ln -sf "$src" "$out/libexec/$tool"
+    done
+  '';
+  qmakeWrapper = writeShellScript "qmake6" ''
+    if [ "$1" = "-query" ]; then
+      case "$2" in
+        QT_HOST_LIBEXECS|QT_HOST_LIBEXECS/get|QT_INSTALL_LIBEXECS|QT_INSTALL_LIBEXECS/get)
+          echo "${qtBuildTools}/libexec"; exit 0;;
+        QT_HOST_BINS|QT_HOST_BINS/get|QT_INSTALL_BINS|QT_INSTALL_BINS/get)
+          echo "${qtBuildTools}/bin"; exit 0;;
+      esac
+    fi
+    exec ${qt6.qtbase}/bin/qmake6 "$@"
+  '';
+in
+rustPlatform.buildRustPackage {
+  pname = "nova-plugin";
+  version = "0.1.0";
+  src = lib.cleanSource ../plugin;
+  cargoLock.lockFile = ../plugin/Cargo.lock;
+
+  nativeBuildInputs = [
+    pkg-config
+    qt6.qtbase
+    qt6.qtdeclarative
+  ];
+
+  buildInputs = [
+    qt6.qtbase
+    qt6.qtdeclarative
+  ];
+
+  dontWrapQtApps = true;
+
+  # qt6.qtbase's setup hook overrides QMAKE after derivation attrs are set,
+  # so re-assert it in preBuild which runs after all setup hooks.
+  preBuild = ''
+    export QMAKE=${qmakeWrapper}
+  '';
+
+  installPhase = ''
+    runHook preInstall
+
+    qml_dir="$out/lib/qt-6/qml/NovaStats"
+    mkdir -p "$qml_dir"
+
+    install -m755 target/*/release/libnova_plugin.so "$qml_dir/"
+    install -m644 target/*/cxxqt/qml_modules/NovaStats/qmldir "$qml_dir/"
+    install -m644 target/*/cxxqt/qml_modules/NovaStats/plugin.qmltypes "$qml_dir/" 2>/dev/null || true
+
+    runHook postInstall
+  '';
+
+  meta = {
+    description = "In-process system stats QML plugin for nova-shell";
+    platforms = lib.platforms.linux;
+  };
+}