Add environment {} config section

niri-config/src/lib.rs

@@ -39,6 +39,8 @@ pub struct Config {
     pub hotkey_overlay: HotkeyOverlay,
     #[knuffel(child, default)]
     pub animations: Animations,
+    #[knuffel(child, default)]
+    pub environment: Environment,
     #[knuffel(children(name = "window-rule"))]
     pub window_rules: Vec<WindowRule>,
     #[knuffel(child, default)]
@@ -572,6 +574,17 @@ pub enum AnimationCurve {
     EaseOutExpo,
 }
 
+#[derive(knuffel::Decode, Debug, Default, Clone, PartialEq, Eq)]
+pub struct Environment(#[knuffel(children)] pub Vec<EnvironmentVariable>);
+
+#[derive(knuffel::Decode, Debug, Clone, PartialEq, Eq)]
+pub struct EnvironmentVariable {
+    #[knuffel(node_name)]
+    pub name: String,
+    #[knuffel(argument)]
+    pub value: Option<String>,
+}
+
 #[derive(knuffel::Decode, Debug, Default, Clone, PartialEq)]
 pub struct WindowRule {
     #[knuffel(children(name = "match"))]
@@ -1061,6 +1074,11 @@ mod tests {
                 }
             }
 
+            environment {
+                QT_QPA_PLATFORM "wayland"
+                DISPLAY null
+            }
+
             window-rule {
                 match app-id=".*alacritty"
                 exclude title="~"
@@ -1217,6 +1235,16 @@ mod tests {
                     },
                     ..Default::default()
                 },
+                environment: Environment(vec![
+                    EnvironmentVariable {
+                        name: String::from("QT_QPA_PLATFORM"),
+                        value: Some(String::from("wayland")),
+                    },
+                    EnvironmentVariable {
+                        name: String::from("DISPLAY"),
+                        value: None,
+                    },
+                ]),
                 window_rules: vec![WindowRule {
                     matches: vec![Match {
                         app_id: Some(Regex::new(".*alacritty").unwrap()),

resources/default-config.kdl

@@ -199,6 +199,15 @@ layout {
 // which may be more convenient to use.
 // spawn-at-startup "alacritty" "-e" "fish"
 
+// You can override environment variables for processes spawned by niri.
+environment {
+    // Set a variable like this:
+    // QT_QPA_PLATFORM "wayland"
+
+    // Remove a variable by using null as the value:
+    // DISPLAY null
+}
+
 cursor {
     // Change the theme and size of the cursor as well as set the
     // `XCURSOR_THEME` and `XCURSOR_SIZE` env variables.

src/main.rs

@@ -15,7 +15,9 @@ use niri::cli::{Cli, Sub};
 use niri::dbus;
 use niri::ipc::client::handle_msg;
 use niri::niri::State;
-use niri::utils::spawning::{spawn, REMOVE_ENV_RUST_BACKTRACE, REMOVE_ENV_RUST_LIB_BACKTRACE};
+use niri::utils::spawning::{
+    spawn, CHILD_ENV, REMOVE_ENV_RUST_BACKTRACE, REMOVE_ENV_RUST_LIB_BACKTRACE,
+};
 use niri::utils::watcher::Watcher;
 use niri::utils::{cause_panic, version, IS_SYSTEMD_SERVICE};
 use niri_config::Config;
@@ -161,6 +163,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     animation::ANIMATION_SLOWDOWN.store(slowdown, Ordering::Relaxed);
 
     let spawn_at_startup = mem::take(&mut config.spawn_at_startup);
+    *CHILD_ENV.write().unwrap() = mem::take(&mut config.environment);
 
     // Create the compositor.
     let mut event_loop = EventLoop::try_new().unwrap();

src/niri.rs

@@ -104,6 +104,7 @@ use crate::ui::config_error_notification::ConfigErrorNotification;
 use crate::ui::exit_confirm_dialog::ExitConfirmDialog;
 use crate::ui::hotkey_overlay::HotkeyOverlay;
 use crate::ui::screenshot_ui::{ScreenshotUi, ScreenshotUiRenderElement};
+use crate::utils::spawning::CHILD_ENV;
 use crate::utils::{
     center, get_monotonic_time, make_screenshot_path, output_size, write_png_rgba8,
 };
@@ -577,7 +578,7 @@ impl State {
     pub fn reload_config(&mut self, path: PathBuf) {
         let _span = tracy_client::span!("State::reload_config");
 
-        let config = match Config::load(&path) {
+        let mut config = match Config::load(&path) {
             Ok(config) => config,
             Err(err) => {
                 warn!("{:?}", err.context("error loading config"));
@@ -598,6 +599,8 @@ impl State {
         };
         animation::ANIMATION_SLOWDOWN.store(slowdown, Ordering::Relaxed);
 
+        *CHILD_ENV.write().unwrap() = mem::take(&mut config.environment);
+
         let mut reload_xkb = None;
         let mut libinput_config_changed = false;
         let mut output_config_changed = false;

src/utils/spawning.rs

@@ -4,9 +4,11 @@ use std::os::unix::process::CommandExt;
 use std::path::Path;
 use std::process::{Command, Stdio};
 use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::RwLock;
 use std::{io, thread};
 
 use libc::close_range;
+use niri_config::Environment;
 use smithay::reexports::rustix;
 use smithay::reexports::rustix::io::{close, read, retry_on_intr, write};
 use smithay::reexports::rustix::pipe::{pipe_with, PipeFlags};
@@ -15,6 +17,7 @@ use crate::utils::expand_home;
 
 pub static REMOVE_ENV_RUST_BACKTRACE: AtomicBool = AtomicBool::new(false);
 pub static REMOVE_ENV_RUST_LIB_BACKTRACE: AtomicBool = AtomicBool::new(false);
+pub static CHILD_ENV: RwLock<Environment> = RwLock::new(Environment(Vec::new()));
 
 /// Spawns the command to run independently of the compositor.
 pub fn spawn<T: AsRef<OsStr> + Send + 'static>(command: Vec<T>) {
@@ -67,6 +70,17 @@ fn spawn_sync(command: impl AsRef<OsStr>, args: impl IntoIterator<Item = impl As
         process.env_remove("RUST_LIB_BACKTRACE");
     }
 
+    // Set configured environment.
+    let env = CHILD_ENV.read().unwrap();
+    for var in &env.0 {
+        if let Some(value) = &var.value {
+            process.env(&var.name, value);
+        } else {
+            process.env_remove(&var.name);
+        }
+    }
+    drop(env);
+
     // When running as a systemd session, we want to put children into their own transient scopes
     // in order to separate them from the niri process. This is helpful for example to prevent the
     // OOM killer from taking down niri together with a misbehaving client.