Trying to run `monitor_record` on Wayland

[korken89]

Hi, thanks for making this library!

I've been trying to get screen recording working on Wayland, and if I run the monitor_record example I get the following error:

thread 'main' panicked at examples/monitor_record.rs:7:57:
called `Result::unwrap()` on an `Err` value: ZbusError(Variant(Message("Can only decode Option<T> from D-Bus format if `option-as-array` feature is enabled")))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Enabling that option in Cargo.toml gives the following error instead:

thread 'main' panicked at examples/monitor_record.rs:7:57:
called `Result::unwrap()` on an `Err` value: ZbusError(Variant(SignatureMismatch(Variant, "an array or dict")))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

How would I help in debug this issue here?

[korken89]

Just to help the error originates at least the following call in wayland_video_recorder.rs:140:

pub fn start(&self, session: &OwnedObjectPath) -> XCapResult<ScreenCastStartResponse> {
    ...

    wait_zbus_response(&portal_request) // <<<<<--------- This one fails
}

[korken89]

It is the deserialize that's failing in wait_zbus_response, so I dumped the response using

    let (code, map): (u32, HashMap<String, Value>) = body.deserialize()?;
    println!("code: {}", code);
    println!("map: {:?}", map);

which gives:

code: 0
map: {"streams": Array(Array { elements: [Structure(Structure { fields: [U32(83), Dict(Dict { map: {Str("id"): Value(Str("0")), Str("position"): Value(Structure(Structure { fields: [I32(0), I32(0)], signature: Structure(Dynamic { fields: [I32, I32] }) })), Str("size"): Value(Structure(Structure { fields: [I32(1962), I32(1226)], signature: Structure(Dynamic { fields: [I32, I32] }) })), Str("source_type"): Value(U32(1))}, signature: Dict { key: Dynamic { child: Str }, value: Dynamic { child: Variant } } })], signature: Structure(Dynamic { fields: [U32, Dict { key: Dynamic { child: Str }, value: Dynamic { child: Variant } }] }) })], signature: Array(Dynamic { child: Structure(Dynamic { fields: [U32, Dict { key: Dynamic { child: Str }, value: Dynamic { child: Variant } }] }) }) })}

Something is not deserializing correctly with ScreenCastStartResponse or ScreenCastStartStream, but I've not been able to figure out what yet. I'll leave this here if anyone is used to looking at this :)

[nashaofu]

What system are you using? Let me see if I can reproduce it.

[korken89]

Hi, thank for coming back! I'm running a laptop as follows:

OS: NixOS 25.11.20250607.3
Host: Lenovo Yoga Slim 7x Snapdragon (LNVNB161216)
Kernel: 6.15.0
Resolution: 2944x1840
DE: niri (Wayland)
WM: sway
CPU: ARM aarch64 (Snapdragon(R) X Elite - X1E78100 - Qualcomm(R) Oryon(TM) CPU)
GPU: Adreno X1-85 iGPU
Memory: 32 GB

[korken89]

I could dump the response as a byte slice, so you can get the actual data. Would that help?

[KamWithK]

Hi, thank for coming back! I'm running a laptop as follows:

OS: NixOS 25.11.20250607.3 Host: Lenovo Yoga Slim 7x Snapdragon (LNVNB161216) Kernel: 6.15.0 Resolution: 2944x1840 DE: niri (Wayland) WM: sway CPU: ARM aarch64 (Snapdragon(R) X Elite - X1E78100 - Qualcomm(R) Oryon(TM) CPU) GPU: Adreno X1-85 iGPU Memory: 32 GB

Would you by any chance be able to share your flake? I'm trying to use this on Nix too but haven't been able to get past some dbus errors at runtime

[korken89]

Absolutely!
Here is the flake:

{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    fenix = {
      url = "github:nix-community/fenix";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };
  outputs =
    {
      nixpkgs,
      fenix,
      ...
    }:
    let
      # forAllSystems follows this guide:
      # https://github.com/Misterio77/nix-starter-configs/issues/64#issuecomment-1941420712
      pkgsFor =
        system:
        let
          pkgs = import nixpkgs {
            inherit system;
            overlays = [
              fenix.overlays.default
            ];
          };
        in
        {
          inherit system pkgs;
          rustToolchain = pkgs.fenix.fromToolchainFile {
            dir = ./.;
            sha256 = "sha256-X/4ZBHO3iW0fOenQ3foEvscgAPJYl2abspaBThDOukI=";
          };
        };
      systems = [
        "aarch64-linux"
        "x86_64-linux"
      ];
      forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f (pkgsFor system));
    in
    {
      formatter = forAllSystems ({ pkgs, ... }: pkgs.nixfmt-tree);
      devShells = forAllSystems (
        {
          system,
          pkgs,
          rustToolchain,
          ...
        }:
        {
          default =
            with pkgs;
            let
              clang = llvmPackages_20.libclang;
              libClangPath = "${clang.lib}/lib";
            in
            pkgs.mkShell.override
              {
                stdenv = llvmPackages_20.stdenv;
              }
              {
                shellHook = ''
                  echo "clang : ${clang.lib}/lib."
                '';
                packages = [
                  egl-wayland
                  libGL
                  pipewire
                  pkg-config
                  wayland
                  xorg.libxcb
                  xorg.libXrandr
                  libgbm
                  dbus
                ];
                LIBCLANG_PATH = libClangPath;
              };
        }
      );
    };
}

rust-toolchain.toml:

[toolchain]
channel = "1.87.0"
components = [
    "clippy",
    "rust-src",
    "rustfmt",
    "rust-analyzer",
    "llvm-tools"
]

[KamWithK]

Absolutely! Here is the flake:

{
inputs = {
nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
fenix = {
url = "github:nix-community/fenix";
inputs.nixpkgs.follows = "nixpkgs";
};
};
outputs =
{
nixpkgs,
fenix,
...
}:
let
# forAllSystems follows this guide:
# Misterio77/nix-starter-configs#64 (comment)
pkgsFor =
system:
let
pkgs = import nixpkgs {
inherit system;
overlays = [
fenix.overlays.default
];
};
in
{
inherit system pkgs;
rustToolchain = pkgs.fenix.fromToolchainFile {
dir = ./.;
sha256 = "sha256-X/4ZBHO3iW0fOenQ3foEvscgAPJYl2abspaBThDOukI=";
};
};
systems = [
"aarch64-linux"
"x86_64-linux"
];
forAllSystems = f: nixpkgs.lib.genAttrs systems (system: f (pkgsFor system));
in
{
formatter = forAllSystems ({ pkgs, ... }: pkgs.nixfmt-tree);
devShells = forAllSystems (
{
system,
pkgs,
rustToolchain,
...
}:
{
default =
with pkgs;
let
clang = llvmPackages_20.libclang;
libClangPath = "${clang.lib}/lib";
in
pkgs.mkShell.override
{
stdenv = llvmPackages_20.stdenv;
}
{
shellHook = ''
echo "clang : ${clang.lib}/lib."
'';
packages = [
egl-wayland
libGL
pipewire
pkg-config
wayland
xorg.libxcb
xorg.libXrandr
libgbm
dbus
];
LIBCLANG_PATH = libClangPath;
};
}
);
};
}

rust-toolchain.toml:

[toolchain]
channel = "1.87.0"
components = [
"clippy",
"rust-src",
"rustfmt",
"rust-analyzer",
"llvm-tools"
]

Yeah I get the same error as you do

[KamWithK]

So I've been debugging and looks like I was right that my error was a bit different to yours

I needed to add a wait_zbus_response (or .next()) into select_sources, and now I reach the exact same problem as here
This was maybe because I'm using tokio?

Maybe the needed types can be auto generated?

[korken89]

Thanks for verifying! Then I'm not the only one :)
I want to give this as look in the coming week again, we have holidays on Sweden this weekend 🚀

[KamWithK]

Thanks for verifying! Then I'm not the only one :) I want to give this as look in the coming week again, we have holidays on Sweden this weekend 🚀

Yeah sure, I tried debugging a load yesterday but I didn't make any real progress, zbus is really confusing and hard to understand what types it wants

Tried to auto generate them too and it gave me this:

    fn start(
        &self,
        session_handle: &zbus::zvariant::ObjectPath<'_>,
        parent_window: &str,
        options: std::collections::HashMap<&str, &zbus::zvariant::Value<'_>>,
    ) -> zbus::Result<zbus::zvariant::OwnedObjectPath>;

But when I tried to use that as my output type I get some trait violations for whatever reason