[UI redesign 1/3] rog-control-center: build .mo from .po at build time

.gitignore

@@ -28,5 +28,9 @@ AGENTS.md
 
 *.log
 
+# Compiled gettext binaries — .po sources are tracked, .mo are build artifacts
+# compiled from source at build time (see rog-control-center/build.rs).
+*.mo
+
 # Git should not follow this IN ANY CASE
 Cargo.lock

rog-control-center/build.rs

@@ -2,8 +2,45 @@ use std::path::PathBuf;
 
 use slint_build::CompilerConfiguration;
 
+/// Compile .po source files to .mo binaries at build time so dev builds
+/// have translations without committing binary artifacts to Git.
+/// Silently skips if `msgfmt` is not installed (installed packages use
+/// /usr/share/locale/ instead).
+fn compile_locales() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let translations_dir = PathBuf::from(root).join("translations");
+    let Ok(entries) = std::fs::read_dir(&translations_dir) else {
+        return;
+    };
+    for entry in entries.flatten() {
+        // Sources live at translations/<locale>/rog-control-center.po; the
+        // compiled catalog goes to the gettext layout (<locale>/LC_MESSAGES/)
+        // that init_translations! resolves at runtime.
+        let po = entry.path().join("rog-control-center.po");
+        if !po.exists() {
+            continue;
+        }
+        let mo = entry.path().join("LC_MESSAGES/rog-control-center.mo");
+        // The LC_MESSAGES dir isn't tracked once the .mo are gitignored, so
+        // recreate it on a fresh checkout before msgfmt writes into it.
+        let _ = std::fs::create_dir_all(mo.parent().unwrap_or(entry.path().as_path()));
+        match std::process::Command::new("msgfmt").arg("-o").arg(&mo).arg(&po).status() {
+            Ok(status) if !status.success() => {
+                println!("cargo:warning=msgfmt failed for {} (status {status})", po.display());
+            }
+            // msgfmt not installed (dev without gettext) — packaged builds use
+            // /usr/share/locale instead, so silently skip.
+            Err(e) if e.kind() == std::io::ErrorKind::NotFound => {}
+            Err(e) => {
+                println!("cargo:warning=msgfmt could not run for {}: {e}", po.display());
+            }
+            Ok(_) => {}
+        }
+    }
+}
+
 fn main() -> Result<(), Box<dyn std::error::Error>> {
-    // write_locales();
+    compile_locales();
     let root = env!("CARGO_MANIFEST_DIR");
     let mut main = PathBuf::from(root);
     main.push("ui/main_window.slint");