feat(resources): load the user's own hatch patterns and linetypes

*.pat files in <config>/patterns and *.lin files in <config>/linetypes
are read after the bundled catalogs, next to the fonts folder SHX
files already resolve from.

Fixes #1725

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/io/linetypes.rs

@@ -69,7 +69,7 @@ static COMPLEX_CATALOG: OnceLock<HashMap<String, ComplexLt>> = OnceLock::new();
 /// Returns `None` for simple (dash-only) linetypes or unknown names.
 pub fn complex_lt(name: &str) -> Option<&'static ComplexLt> {
     COMPLEX_CATALOG
-        .get_or_init(|| parse_complex(LIN_SOURCE))
+        .get_or_init(|| parse_complex(lin_source()))
         .get(&name.to_ascii_uppercase())
 }
 
@@ -232,6 +232,14 @@ pub fn resolve_complex_lt(document: &CadDocument, name: &str) -> Option<ComplexL
 
 const LIN_SOURCE: &str = include_str!("../../assets/linetypes/OpenCADStudio.lin");
 
+/// The bundled linetypes followed by the user's own `.lin` files.
+fn lin_source() -> &'static str {
+    static SOURCE: OnceLock<String> = OnceLock::new();
+    SOURCE.get_or_init(|| {
+        format!("{LIN_SOURCE}\n{}", crate::io::patterns::user_definitions("linetypes", "lin"))
+    })
+}
+
 // ── Pattern art extraction ────────────────────────────────────────────────
 
 /// Extract the ASCII-art portion of a LIN description.
@@ -257,7 +265,7 @@ pub fn extract_pattern(desc: &str) -> String {
 
 /// Add all standard OpenCADStudio linetypes to `doc`, skipping existing ones.
 pub fn populate_document(doc: &mut CadDocument) {
-    populate_document_from_source(doc, LIN_SOURCE);
+    populate_document_from_source(doc, lin_source());
 }
 
 /// Add the linetypes of a caller-supplied `.lin` source, embedded shapes and

src/io/patterns.rs

@@ -39,9 +39,41 @@ pub struct PatternDef {
 
 static CATALOG: OnceLock<Vec<PatternDef>> = OnceLock::new();
 
-/// All parsed patterns, in file order.
+/// All parsed patterns, in file order: the bundled catalog, then the user's
+/// own `.pat` files.
 pub fn catalog() -> &'static [PatternDef] {
-    CATALOG.get_or_init(|| parse(PAT_SRC))
+    CATALOG.get_or_init(|| parse(&format!("{PAT_SRC}\n{}", user_definitions("patterns", "pat"))))
+}
+
+/// The text of every `*.<ext>` file in `<config>/<folder>`, where users drop
+/// their own hatch patterns and linetypes. Bundled names come first, so a
+/// user file adds definitions rather than replacing the built-in ones.
+#[cfg(not(target_arch = "wasm32"))]
+pub(crate) fn user_definitions(folder: &str, ext: &str) -> String {
+    let Some(dir) = crate::config::config_dir().map(|dir| dir.join(folder)) else {
+        return String::new();
+    };
+    let Ok(entries) = std::fs::read_dir(dir) else {
+        return String::new();
+    };
+    let mut paths: Vec<_> = entries
+        .filter_map(Result::ok)
+        .map(|entry| entry.path())
+        .filter(|path| path.extension().is_some_and(|e| e.eq_ignore_ascii_case(ext)))
+        .collect();
+    paths.sort();
+    paths
+        .iter()
+        .filter_map(|path| std::fs::read(path).ok())
+        .map(|bytes| String::from_utf8_lossy(&bytes).into_owned())
+        .collect::<Vec<_>>()
+        .join("\n")
+}
+
+/// The web build has no user folder.
+#[cfg(target_arch = "wasm32")]
+pub(crate) fn user_definitions(_folder: &str, _ext: &str) -> String {
+    String::new()
 }
 
 // ── Geometry helper ───────────────────────────────────────────────────────