Merge pull request 'feat(doctor): the one host prerequisite the Asset Bridge added (Asset Bridge cutover, 4 of 5)' (#26) from edge into main

Reviewed-on: #26
Reviewed-by: Colby Whitlock <whitlocktech@gmail.com>

src/doctor.rs

@@ -158,6 +158,10 @@ pub fn run(cli: &Cli) -> Result<i32> {
     // ── The bundle ───────────────────────────────────────────────────────────
     rows.push(bundle_row(&record));
 
+    // ── The host ─────────────────────────────────────────────────────────────
+    // Linux only, and absent entirely elsewhere (see `imaging_row`).
+    rows.extend(imaging_row());
+
     // ── Backups ──────────────────────────────────────────────────────────────
     rows.push(backup_row(&layout));
 
@@ -755,6 +759,71 @@ fn bundle_row(record: &InstallRecord) -> Row {
     Row::warn("Bundle", detail).note("run `update` to move both halves to one checked combination")
 }
 
+/// `libgdiplus` on a Linux shard host — the one host prerequisite the Asset Bridge added
+/// (docs/link/v8.md §4.4, docs/link/SHARD_PREREQS.md).
+///
+/// ServUO targets `net48`, so on Linux it runs under Mono, and Mono's `System.Drawing` is a thin
+/// layer over this library — which sits in the **decode** path, not merely the encode: without it
+/// the shard cannot read a single sprite out of the operator's UO client. Windows hosts ship
+/// `System.Drawing` with .NET Framework and need nothing, which is why this row exists only on
+/// Linux rather than reporting "not applicable" on three quarters of the hosts that run it.
+///
+/// **A `⚠`, never a `✗`.** Everything else on this plane works without it: the cliloc table and
+/// the shard's own spawn files have no pixels in them, and a bridge that serves names and an atlas
+/// but no artwork is a working bridge with one feature missing. It is also not the last word — the
+/// shard reports `NO_IMAGING` on the asset plane itself, from inside the process that would do the
+/// decoding. This row exists to move that discovery from "the bestiary is empty, weeks later" to
+/// "the host is missing a package, now".
+#[cfg(target_os = "linux")]
+fn imaging_row() -> Option<Row> {
+    Some(imaging_verdict(imaging_present()))
+}
+
+/// Is the library on this host? Two answers, in the order that is most likely to be right.
+#[cfg(target_os = "linux")]
+fn imaging_present() -> bool {
+    // `ldconfig -p` is the loader's own cache, which is the same question Mono asks at runtime —
+    // strictly better than probing paths, because a distro that puts the file somewhere unusual has
+    // told the loader about it and would otherwise read here as missing.
+    let cached = crate::util::run("ldconfig", &["-p"])
+        .ok()
+        .map(|o| String::from_utf8_lossy(&o.stdout).contains("libgdiplus.so"))
+        .unwrap_or(false);
+
+    // The fallback is for a host with no `ldconfig` on PATH (a slim container, mostly), where a
+    // present library would otherwise be reported absent.
+    cached
+        || [
+            "/usr/lib/libgdiplus.so",
+            "/usr/lib64/libgdiplus.so",
+            "/usr/lib/x86_64-linux-gnu/libgdiplus.so",
+            "/usr/lib/aarch64-linux-gnu/libgdiplus.so",
+            "/usr/local/lib/libgdiplus.so",
+        ]
+        .iter()
+        .any(|p| Path::new(p).exists())
+}
+
+/// The operator-visible half, split out so the wording and the mark are testable on a host that
+/// has the library and on one that does not — which the detection itself is not.
+#[cfg(target_os = "linux")]
+fn imaging_verdict(found: bool) -> Row {
+    if found {
+        return Row::ok("Imaging (libgdiplus)", "present");
+    }
+    Row::warn("Imaging (libgdiplus)", "not found on this host")
+        .note("this shard cannot decode artwork out of its UO client — creature portraits and")
+        .note("item pictures will be absent; names and the spawn atlas are unaffected")
+        .note("install it: apt-get install libgdiplus  /  dnf install libgdiplus")
+        .note("see docs/link/SHARD_PREREQS.md — Windows hosts need nothing")
+}
+
+/// Windows and macOS hosts do not need it, so there is no row to print.
+#[cfg(not(target_os = "linux"))]
+fn imaging_row() -> Option<Row> {
+    None
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -913,4 +982,39 @@ mod tests {
         assert_eq!(row.mark, Mark::Ok);
         assert!(row.detail.contains("operator-owned"), "{}", row.detail);
     }
+
+    // ── The host row (Linux only; see `imaging_row`) ─────────────────────────
+
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn a_missing_libgdiplus_warns_and_names_the_package() {
+        let row = imaging_verdict(false);
+        // A ⚠, never a ✗: the cliloc table and the spawn atlas have no pixels in them, so a host
+        // without this library still runs a useful bridge. `doctor`'s exit code must not turn red
+        // over one absent feature.
+        assert_eq!(row.mark, Mark::Warn);
+        let notes = row.notes.join(" ");
+        assert!(notes.contains("apt-get install libgdiplus"), "{notes}");
+        assert!(notes.contains("SHARD_PREREQS.md"), "{notes}");
+    }
+
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn a_present_libgdiplus_is_one_quiet_ok_line() {
+        let row = imaging_verdict(true);
+        assert_eq!(row.mark, Mark::Ok);
+        assert!(
+            row.notes.is_empty(),
+            "a satisfied prerequisite needs no advice"
+        );
+    }
+
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn detection_answers_rather_than_panicking_on_a_host_with_no_ldconfig() {
+        // The value depends on the host and is not asserted — what is asserted is that a missing
+        // `ldconfig` degrades to the path probe instead of taking `doctor` down, which is the rule
+        // every row in this module follows.
+        let _ = imaging_present();
+    }
 }