Merge #1238: Fix duplicate SVG ids when a layer name matches a generated id (@Silvertree2010)

# Conflicts:
#	crates/svg/src/tests.rs

crates/svg/src/lib.rs

@@ -162,8 +162,13 @@ fn hex(c: Color) -> String {
 
 impl W<'_> {
     fn id(&mut self, prefix: &str) -> String {
-        self.next += 1;
-        format!("{prefix}{}", self.next)
+        loop {
+            self.next += 1;
+            let id = format!("{prefix}{}", self.next);
+            if self.used_ids.insert(id.clone()) {
+                return id;
+            }
+        }
     }
 
     /// `fill="..." [fill-opacity]` for a paint on a w×h box; `None` when it paints nothing.

crates/svg/src/tests.rs

@@ -208,3 +208,14 @@ fn unique_id_is_linear_for_repeated_names() {
     assert_eq!(w.unique_id("Rectangle"), "Rectangle_30001");
     assert!(start.elapsed() < std::time::Duration::from_secs(2), "unique_id is quadratic: {:?}", start.elapsed());
 }
+
+#[test]
+fn layer_ids_never_clash_with_generated_ids() {
+    let mut d = Document::new("t");
+    let p = d.first_page().unwrap();
+    let f = d.create(p, NodeKind::Frame, "clip1", 0.0, 0.0, 100.0, 100.0).unwrap();
+    d.get_mut(f).unwrap().clip = true;
+    d.create(f, NodeKind::Rectangle, "R", 0.0, 0.0, 50.0, 50.0).unwrap();
+    let svg = export_svg(&d, &[f], &SvgOptions { include_ids: true, ..SvgOptions::default() }).unwrap();
+    assert_eq!(svg.matches("id=\"clip1\"").count(), 1, "{svg}");
+}