# Dev shell for the Slint front-end.
#
# NixOS has no rustup-installed toolchain here, and Slint's renderers link against
# system GL/X11/Wayland libraries that a plain `cargo build` cannot find on its own -
# hence LD_LIBRARY_PATH below rather than just a list of buildInputs.
{ pkgs ? import <nixpkgs> { } }:

let
  # Everything the winit backend dlopen()s at runtime. Missing one of these shows up
  # as a panic inside winit, not as a link error, so they are easy to misdiagnose.
  runtimeLibs = with pkgs; [
    libGL
    libxkbcommon
    wayland
    xorg.libX11
    xorg.libXcursor
    xorg.libXi
    xorg.libXrandr
    fontconfig
    freetype
  ];
in
pkgs.mkShell {
  nativeBuildInputs = with pkgs; [
    cargo
    rustc
    rustfmt
    clippy
    pkg-config
    # Only needed when building with --features skia: rust-skia compiles its own
    # bindings shim and wants a C++ toolchain plus python for the GN build.
    clang
    python3
  ];

  # Nunito is the face the design is drawn in. The web front-end self-hosts it as
  # woff2, which Slint cannot read, so the dev shell points Slint at the TTF instead
  # (`SLINT_DEFAULT_FONT` takes one file and makes it the primary font). Without it
  # everything still renders, in whatever sans fontconfig hands back.
  SLINT_DEFAULT_FONT =
    "${pkgs.nunito}/share/fonts/truetype/Nunito/Nunito[wght].ttf";

  buildInputs = runtimeLibs ++ (with pkgs; [
    fontconfig
    # libinput/libdrm/libseat are the linuxkms (kiosk) backend's dependencies. They
    # cost nothing to have present on a desktop build.
    libinput
    libdrm
    seatd
    udev
  ]);

  LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath runtimeLibs;

  # rust-skia downloads a prebuilt libskia rather than building it, when it can.
  SKIA_BINARIES_URL_TEMPLATE = null;

  shellHook = ''
    echo "musicmouse slint-frontend — cargo $(cargo --version | cut -d' ' -f2)"
    echo "  cargo run                      # windowed, femtovg"
    echo "  cargo run --features skia      # windowed, skia (what the Pi uses)"
    echo "  cargo build --features kiosk   # linuxkms + skia, for the device"
  '';
}