Add XWayland support (#16)

* save dev state

* fix xwayland-satellite supervisor lifecycle, readiness and cleanup

* remove wayland scanner protocol generated files

* default xwayland enabled with path

* remove jargons

* address x11 review: park unconfirmed cleanup, never signal a reaped group, fix storm test and notify dir mode

* fix resize tests: never build Size values from negative dimensions

* add min-width/min-height window rules that replace client minimum sizes

* rename effective_size_constraints to effective_minimum_size and minor cleanups

compositor/src/session_environment.rs

@@ -0,0 +1,138 @@
+use std::ffi::OsString;
+use std::path::PathBuf;
+use std::process::Command;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) struct X11Environment {
+    pub display: OsString,
+    pub authority: PathBuf,
+}
+
+// Child endpoints are separate from the host endpoints used by the nested backend.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) struct SessionEnvironment {
+    pub wayland_display: OsString,
+    pub x11: Option<X11Environment>,
+}
+
+impl SessionEnvironment {
+    /// Apply before private_client::prepare_command(), which overrides WAYLAND_SOCKET.
+    pub fn apply_public(&self, command: &mut Command) {
+        command
+            .env("WAYLAND_DISPLAY", &self.wayland_display)
+            .env("FERESE_PUBLIC_WAYLAND_DISPLAY", &self.wayland_display)
+            .env_remove("WAYLAND_SOCKET")
+            .env_remove("FERESE_SHELL_CONTROL_SOCKET")
+            .env_remove("DISPLAY")
+            .env_remove("XAUTHORITY");
+
+        if let Some(x11) = &self.x11 {
+            command.env("DISPLAY", &x11.display).env("XAUTHORITY", &x11.authority);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn environment(x11: Option<X11Environment>) -> SessionEnvironment {
+        SessionEnvironment {
+            wayland_display: OsString::from("wayland-7"),
+            x11,
+        }
+    }
+
+    fn rendered(command: &Command) -> Vec<(String, Option<String>)> {
+        command
+            .get_envs()
+            .map(|(key, value)| {
+                (
+                    key.to_string_lossy().into_owned(),
+                    value.map(|value| value.to_string_lossy().into_owned()),
+                )
+            })
+            .collect()
+    }
+
+    fn value_of(command: &Command, key: &str) -> Option<Option<String>> {
+        rendered(command)
+            .into_iter()
+            .find(|(name, _)| name == key)
+            .map(|(_, value)| value)
+    }
+
+    #[test]
+    fn x11_available_publishes_display_and_authority() {
+        let mut command = Command::new("true");
+        environment(Some(X11Environment {
+            display: OsString::from(":7"),
+            authority: PathBuf::from("/run/user/1000/ferese-xauth-abc"),
+        }))
+        .apply_public(&mut command);
+
+        assert_eq!(value_of(&command, "DISPLAY"), Some(Some(":7".to_owned())));
+        assert_eq!(
+            value_of(&command, "XAUTHORITY"),
+            Some(Some("/run/user/1000/ferese-xauth-abc".to_owned()))
+        );
+        assert_eq!(
+            value_of(&command, "WAYLAND_DISPLAY"),
+            Some(Some("wayland-7".to_owned()))
+        );
+    }
+
+    #[test]
+    fn x11_unavailable_removes_display_and_authority() {
+        let mut command = Command::new("true");
+        environment(None).apply_public(&mut command);
+
+        assert_eq!(value_of(&command, "DISPLAY"), Some(None));
+        assert_eq!(value_of(&command, "XAUTHORITY"), Some(None));
+    }
+
+    #[test]
+    fn the_host_private_socket_is_always_cleared() {
+        let mut command = Command::new("true");
+        environment(None).apply_public(&mut command);
+
+        assert_eq!(value_of(&command, "WAYLAND_SOCKET"), Some(None));
+        assert_eq!(value_of(&command, "FERESE_SHELL_CONTROL_SOCKET"), Some(None));
+    }
+
+    #[test]
+    fn the_public_socket_is_exported_for_shell_launched_apps() {
+        let mut command = Command::new("true");
+        environment(None).apply_public(&mut command);
+
+        assert_eq!(
+            value_of(&command, "FERESE_PUBLIC_WAYLAND_DISPLAY"),
+            Some(Some("wayland-7".to_owned()))
+        );
+    }
+
+    #[test]
+    fn unrelated_variables_are_left_alone() {
+        let mut command = Command::new("true");
+        command.env("FERESE_COMPOSITOR_WALLPAPER", "1");
+        environment(None).apply_public(&mut command);
+
+        assert_eq!(
+            value_of(&command, "FERESE_COMPOSITOR_WALLPAPER"),
+            Some(Some("1".to_owned()))
+        );
+    }
+
+    #[test]
+    fn a_host_display_is_replaced_by_the_session_display() {
+        let mut command = Command::new("true");
+        command.env("DISPLAY", ":0");
+        environment(Some(X11Environment {
+            display: OsString::from(":7"),
+            authority: PathBuf::from("/run/user/1000/auth"),
+        }))
+        .apply_public(&mut command);
+
+        assert_eq!(value_of(&command, "DISPLAY"), Some(Some(":7".to_owned())));
+    }
+}