feat: enhance build process for xkbcommon-x11 library linking

README.md

@@ -34,7 +34,7 @@ Required on the Linux host:
 - `ffmpeg` with the `libx264` encoder, and PipeWire's `pw-cat` utility. Hardware encoding additionally needs `h264_vaapi`, a VA-API driver with H.264 encoding support, and access to `/dev/dri/renderD*`.
 - Apple TV on the same reachable network with AirPlay enabled.
 
-The runner handles the missing libxkbcommon-x11 development symlink on this host using a local build directory. A normal `cargo build --locked` also works when all development libraries are installed.
+Plain `cargo run` and `cargo build --locked` work on this host. For native Linux GUI builds, `build.rs` supplies a build-local xkbcommon-x11 linker symlink when the compiler can find the runtime library but its development symlink is missing. No system files are changed. If neither library is installed, install the distribution’s xkbcommon-x11 development package. Cross-compilation requires the target development libraries.
 
 The development profile optimizes Spielab's packet handling and ChaCha20-Poly1305 dependencies because the development runner is used for live sharing. On this host the isolated 64 KiB video-packet encryption diagnostic fell from approximately 7.8 ms to 0.057 ms per packet. This microbenchmark does not measure display latency.
 

build.rs

@@ -0,0 +1,49 @@
+//! GPUI 0.2.2 links xkbcommon-x11 even with only its Wayland backend enabled.
+//! Some hosts have the runtime SONAME but no development linker symlink.
+use std::{env, path::PathBuf, process::Command};
+
+fn compiler_library(name: &str) -> Option<PathBuf> {
+    let output = Command::new(env::var_os("CC").unwrap_or_else(|| "cc".into()))
+        .arg(format!("-print-file-name={name}"))
+        .output()
+        .ok()?;
+    if !output.status.success() {
+        return None;
+    }
+    let path = PathBuf::from(String::from_utf8(output.stdout).ok()?.trim());
+    path.is_absolute().then_some(path).filter(|p| p.is_file())
+}
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-env-changed=CC");
+    println!("cargo:rerun-if-env-changed=LIBRARY_PATH");
+    if env::var_os("CARGO_FEATURE_GUI").is_none()
+        || env::var("CARGO_CFG_TARGET_OS").as_deref() != Ok("linux")
+        || env::var_os("HOST") != env::var_os("TARGET")
+    {
+        return;
+    }
+    if compiler_library("libxkbcommon-x11.so").is_some() {
+        return;
+    }
+    let Some(runtime) = compiler_library("libxkbcommon-x11.so.0") else {
+        println!(
+            "cargo:warning=Install the xkbcommon-x11 development library (libxkbcommon-x11-devel on Fedora, libxkbcommon-x11-dev on Debian/Ubuntu)"
+        );
+        return;
+    };
+    println!("cargo:rerun-if-changed={}", runtime.display());
+    #[cfg(unix)]
+    {
+        let directory =
+            PathBuf::from(env::var_os("OUT_DIR").expect("Cargo OUT_DIR")).join("native");
+        std::fs::create_dir_all(&directory).expect("Create native linker directory");
+        let link = directory.join("libxkbcommon-x11.so");
+        if link.symlink_metadata().is_ok() {
+            std::fs::remove_file(&link).expect("Refresh native linker symlink");
+        }
+        std::os::unix::fs::symlink(runtime, link).expect("Create xkbcommon-x11 linker symlink");
+        println!("cargo:rustc-link-search=native={}", directory.display());
+    }
+}

scripts/run.sh

@@ -4,20 +4,6 @@ project_root="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
 cd "$project_root"
 export CARGO_HOME="${CARGO_HOME:-$project_root/.cargo-home}"
 
-# Some distributions install the xkbcommon-x11 runtime without its linker name.
-# GPUI 0.2.2 still links this library when built with only its Wayland feature.
-# Provide a build-local linker name; no system library files are modified.
-if ! pkg-config --exists xkbcommon-x11; then
-    for library in /usr/lib64/libxkbcommon-x11.so.0 /usr/lib/x86_64-linux-gnu/libxkbcommon-x11.so.0; do
-        if [[ -f "$library" ]]; then
-            mkdir -p "$project_root/target/native"
-            ln -sf "$library" "$project_root/target/native/libxkbcommon-x11.so"
-            export LIBRARY_PATH="$project_root/target/native${LIBRARY_PATH:+:$LIBRARY_PATH}"
-            break
-        fi
-    done
-fi
-
 # Reuse development pairing identities, when present, across local launches.
 if [[ -d "$project_root/.state" && -z "${SPIELAB_STATE_DIR:-}" ]]; then
     export SPIELAB_STATE_DIR="$project_root/.state"