qdbus => dbus-rs

[LuckyTurtleDev]

I am trying to execute the KDE plasmashell with dbus. I have successfully test the call with qdbus program.
But I was not able to reproduce this with this crate, it does simple panci/return a error.

qdbus org.kde.plasmashell /PlasmaShell org.kde.PlasmaShell.evaluateScript 'for (const d of desktops()) { print(d); print("\n"); for (const key in d) { print(key); print(" = "); print(d[key]); print("\n"); } print("\n\n"); }'

let interface = "org.kde.plasmashell";
let path = "/PlasmaShell/org.kde.PlasmaShell";
let method = "evaluateScript";
let args = ("to", "do");
let timeout = Duration::from_millis(5000);
let conn = Connection::new_session().unwrap();
let proxy = conn.with_proxy(interface, path, timeout);  //line 12
let (res,): (Vec<String>,) = proxy.method_call(interface, method, args).unwrap();

    Finished dev [unoptimized + debuginfo] target(s) in 1.50s
     Running `/home/lukas/git/more-wallpapers/target/debug/mwallpapers list`
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: "Object path was not valid: '/PlasmaShell/org.kde.PlasmaShell'"', /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/dbus-0.9.5/src/strings.rs:187:1
stack backtrace:
   0: rust_begin_unwind
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/std/src/panicking.rs:584:5
   1: core::panicking::panic_fmt
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/panicking.rs:143:14
   2: core::result::unwrap_failed
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/result.rs:1785:5
   3: core::result::Result<T,E>::unwrap
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/result.rs:1078:23
   4: <dbus::strings::Path as core::convert::From<&str>>::from
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/dbus-0.9.5/src/strings.rs:111:69
   5: <T as core::convert::Into<U>>::into
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/convert/mod.rs:550:9
   6: dbus::blocking::Connection::with_proxy
             at /home/lukas/.cargo/registry/src/github.com-1ecc6299db9ec823/dbus-0.9.5/src/blocking.rs:161:67
   7: more_wallpapers::linux::kde::get_screens
             at /home/lukas/git/more-wallpapers/more-wallpapers/src/linux/kde.rs:12:14
   8: more_wallpapers::linux::get_builder
             at /home/lukas/git/more-wallpapers/more-wallpapers/src/linux/mod.rs:25:22
   9: more_wallpapers::WallpaperBuilder::new
             at /home/lukas/git/more-wallpapers/more-wallpapers/src/lib.rs:69:3
  10: mwallpapers::list
             at ./src/main.rs:10:16
  11: mwallpapers::main
             at ./src/main.rs:25:16
  12: core::ops::function::FnOnce::call_once
             at /rustc/fe5b13d681f25ee6474be29d748c65adcd91f69e/library/core/src/ops/function.rs:227:5

I am not sure if I did everything right.

[mulkieran]

Try these lines instead of what you have:

let interface = "org.kde.PlasmaShell";

let path = "/PlasmaShell";

and since that worked w/ qdbus, it should work for your Rust program, in the sense that now the method will be called, and your program won't fail with an invalid object path. You still have to tackle passing the arguments, though.

[diwic]

You need to get the arguments and return values correct also. Is there any documentation for the evaluateScript method?

[chirping78]

From the method name evaluateScript and the qdbus cmd line example in the initial question, I guess the argument should be a single 's'. So this time the error should be caused by this line let args = ("foo", "bar");, try change it to let args = ("var a=1", )

[LuckyTurtleDev]

Thanks for your help it does work now.

	let destination = "org.kde.plasmashell";
	let interface = "org.kde.PlasmaShell";
	let path = "/PlasmaShell";
	let method = "evaluateScript";
	let args = ("print(\"hhi\")",);
	let timeout = Duration::from_millis(5000);
	let conn = Connection::new_session().unwrap();
	let proxy = conn.with_proxy(destination, path, timeout);
	let (names,): (String,) = proxy.method_call(interface, method, args).unwrap();
	println!("{names}");

hhi

Maybe the error message should be adjusted. I would never expect that the argument or the return value was the issue, with this message.

[diwic]

Well, given the amount of trouble you've been having with getting all the parameters right, I recommend the dbus-codegen crate for the next time where (almost) all of that is sorted out for you.

[diwic]

And every error message starting with D-Bus error comes from layers below the D-Bus bindings.