feat: PySide6 dev environment with runnable examplesHEADmain

Flake devShell (PySide6 6.11 on Python 3.13, designer, uic/rcc from
qtbase libexec, offline docs) plus hello_widgets and hello_quick
examples. QML_IMPORT_PATH exported — nixpkgs PySide6 finds platform
plugins on its own but not QML imports; see README.

1 files changed, 45 insertions, 0 deletions

diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..40e09a0
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,45 @@
+{
+  description = "Qt for Python development environment (PySide6, nixos-26.05)";
+
+  inputs = {
+    nixpkgs.url = "github:Nixos/nixpkgs/nixos-26.05";
+  };
+
+  outputs =
+    { self, nixpkgs }:
+    let
+      system = "x86_64-linux";
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      python = pkgs.python3.withPackages (
+        p: with p; [
+          pyside6
+        ]
+      );
+    in
+    {
+      formatter.${system} = pkgs.nixfmt;
+
+      devShells.${system}.default = pkgs.mkShell {
+        packages = [
+          python
+          pkgs.qt6.qttools # designer, linguist, assistant
+          pkgs.qt6.qtdoc # offline documentation for Assistant
+        ];
+
+        # Platform plugins are found automatically (compiled-in store
+        # paths), but QML imports are NOT: without this export, any
+        # "import QtQuick" fails with "module is not installed".
+        shellHook = ''
+          # uic/rcc (with Python codegen via -g python) live in libexec,
+          # not bin, so they are not on PATH by default.
+          export PATH=${pkgs.qt6.qtbase}/libexec:$PATH
+          export QML_IMPORT_PATH=${pkgs.qt6.qtdeclarative}/lib/qt-6/qml
+          export QML2_IMPORT_PATH=$QML_IMPORT_PATH
+          export QT_DOCS=${pkgs.qt6.qtdoc}/share/doc
+          echo "PySide6 $(python -c 'import PySide6; print(PySide6.__version__)') sur Python $(python -V | cut -d' ' -f2)"
+          echo "Exemples dans ./examples — voir README.md"
+        '';
+      };
+    };
+}