Make SVG export of type with control characters well-formed

Found while testing crates/svg/src/export.rs:1908

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

crates/svg/src/export.rs

@@ -166,6 +166,20 @@ fn xml_attr_escape(s: &str) -> String {
     xml_escape(s).replace('\t', "	").replace('\n', "
").replace('\r', "
")
 }
 
+/// Escape type for XML content. Characters XML 1.0 does not allow are dropped, except the line
+/// and page breaks (U+000B, U+000C) other apps paste, which become spaces.
+fn xml_text(s: &str) -> String {
+    let s: String = s
+        .chars()
+        .filter_map(|c| match c {
+            '\u{b}' | '\u{c}' => Some(' '),
+            c if valid_xml_value(c.encode_utf8(&mut [0; 4])) => Some(c),
+            _ => None,
+        })
+        .collect();
+    xml_escape(&s)
+}
+
 fn valid_xml_value(s: &str) -> bool {
     s.chars().all(|c| matches!(c, '\t' | '\n' | '\r' | '\u{20}'..='\u{d7ff}' | '\u{e000}'..='\u{fffd}' | '\u{10000}'..='\u{10ffff}'))
 }
@@ -1905,7 +1919,7 @@ impl Writer<'_> {
             }
             let diff = run_diff(&base.props, self.char_props(st, base.space));
             attrs.push_str(&self.attrs(&diff));
-            let text = xml_escape(&seg.text);
+            let text = xml_text(&seg.text);
             if attrs.is_empty() && fewer {
                 s.push_str(&text);
             } else {
@@ -2010,7 +2024,7 @@ impl Writer<'_> {
         for run in &t.runs {
             let diff = run_diff(&base, self.char_props(&run.style, space));
             let a = self.attrs(&diff);
-            s.push_str(&format!("<tspan{a}>{}</tspan>", xml_escape(&run.text.replace('\n', " "))));
+            s.push_str(&format!("<tspan{a}>{}</tspan>", xml_text(&run.text.replace('\n', " "))));
         }
         s.push_str("</textPath></text>");
         self.line(&s);

crates/svg/tests/roundtrip.rs

@@ -386,6 +386,18 @@ fn text_roundtrip_and_escaping() {
     assert!(t.xf.translation().to_point().distance(Point::new(20.0, 50.0)) < 0.01);
 }
 
+#[test]
+fn text_with_control_characters_exports_well_formed_svg() {
+    // A pasted manual line break (U+000B) or other C0 control character is not allowed in XML 1.0.
+    let t = TextObject::point(Point::new(20.0, 50.0), "A\u{0}\u{8}B\u{b}C\u{fffe}D", CharStyle::default());
+    let id = Document::new(200.0, 200.0).alloc_id();
+    let d = doc_with(vec![Node::new(id, NodeKind::Text(Box::new(t)))]);
+    let s = export(&d, &ExportOptions::default());
+    let r = import(&s).unwrap_or_else(|e| panic!("exported SVG doesn't import: {e:?}"));
+    let NodeKind::Text(t) = &art(&r)[0].kind else { panic!() };
+    assert_eq!(t.plain_text(), "AB CD");
+}
+
 #[test]
 fn scaled_text_roundtrips_at_the_size_it_draws() {
     // Type scaled with its object (its transform scales it) comes back at the size it draws at,