From 843ffb6507ed37185282eead34d0f75cb9e746ef Mon Sep 17 00:00:00 2001
From: Tanish Manku <tmanku.dev@gmail.com>
Date: Wed, 4 Nov 2026 19:58:44 -0700
Subject: [PATCH] Fonts: a registered font outlives a rescan, also beside a
 file of the same stem (CodeRabbit on #2803)

---
 crates/fonts/src/ttf.rs                | 14 +++++++++++---
 crates/fonts/tests/ttf_font_folders.rs |  6 ++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/crates/fonts/src/ttf.rs b/crates/fonts/src/ttf.rs
index 29a8b686c..2f4ffab24 100644
--- a/crates/fonts/src/ttf.rs
+++ b/crates/fonts/src/ttf.rs
@@ -245,6 +245,9 @@ struct Db {
     paths: HashMap<String, Source>,
     /// Loaded or registered font file bytes, by lower-case file stem.
     files: HashMap<String, Arc<Vec<u8>>>,
+    /// The keys of `files` given by [`register`]: kept over a file of the same stem, and by a
+    /// rescan.
+    registered: std::collections::HashSet<String>,
     /// Name lookups already answered, found or not.
     resolved: HashMap<String, Option<Face>>,
     fallback: Fallback,
@@ -454,9 +457,11 @@ pub fn set_font_dirs<S: AsRef<str>>(dirs: &[S]) {
 /// Forget what was found and look for fonts again (files added to a font folder).
 pub fn rescan() {
     let mut g = lock();
-    // Fonts registered by name (no file behind them) stay.
+    // Fonts registered by name stay, also where a found file has the same stem; bytes read
+    // from found files go.
     let paths = std::mem::take(&mut g.paths);
-    g.files.retain(|k, _| !paths.contains_key(k));
+    let Db { files, registered, .. } = &mut *g;
+    files.retain(|k, _| registered.contains(k) || !paths.contains_key(k));
     g.scanned = false;
     g.resolved.clear();
     g.fallback = Fallback::default();
@@ -797,7 +802,9 @@ pub(crate) fn rank_fallback(stems: &[String]) -> Vec<String> {
 /// Register font bytes under a name (web builds and tests).
 pub fn register(name: &str, bytes: Vec<u8>) {
     let mut g = lock();
-    g.files.insert(key(name), Arc::new(bytes));
+    let k = key(name);
+    g.files.insert(k.clone(), Arc::new(bytes));
+    g.registered.insert(k);
     g.resolved.clear();
     g.fallback = Fallback::default();
 }
@@ -809,6 +816,7 @@ pub(crate) fn register_static(name: &str, bytes: &'static [u8]) {
     let mut g = lock();
     let k = key(name);
     g.files.remove(&k);
+    g.registered.remove(&k);
     g.paths.insert(k, Source::Static(bytes));
     g.resolved.clear();
     g.fallback = Fallback::default();
diff --git a/crates/fonts/tests/ttf_font_folders.rs b/crates/fonts/tests/ttf_font_folders.rs
index 6ad257788..e8e3debda 100644
--- a/crates/fonts/tests/ttf_font_folders.rs
+++ b/crates/fonts/tests/ttf_font_folders.rs
@@ -42,6 +42,11 @@ fn a_font_in_a_user_folder_is_found_listed_and_dropped_with_the_folder() {
     if !copy_into(&src, &dir) {
         return;
     }
+    // A font registered by name, with a file of the same stem in the folder: looking for fonts
+    // again (twice, as the folder comes and goes) keeps the registered bytes.
+    let Ok(bytes) = std::fs::read(&src) else { return };
+    let _ = std::fs::copy(&src, dir.join("CadcraftRegistered.ttf"));
+    ttf::register("CadcraftRegistered.ttf", bytes);
     let before = ttf::generation();
     ttf::set_font_dirs(&[dir.to_string_lossy().to_string()]);
     assert!(ttf::generation() > before);
@@ -55,5 +60,6 @@ fn a_font_in_a_user_folder_is_found_listed_and_dropped_with_the_folder() {
     }
     ttf::set_font_dirs::<&str>(&[]);
     assert!(ttf::find("CadcraftTestFace.ttf").is_none());
+    assert!(ttf::find("CadcraftRegistered.ttf").is_some(), "a registered font outlives a rescan");
     let _ = std::fs::remove_dir_all(&dir);
 }