From 8538dd740f58e51ce672ac6ff8674673e683cef3 Mon Sep 17 00:00:00 2001
From: NetterSilver <133535268+Silvertree2010@users.noreply.github.com>
Date: Fri, 16 Oct 2026 03:38:36 +0200
Subject: [PATCH] Refuse edits that leave a layer with non-finite geometry

Found while testing crates/engine/src/cmd/arrange.rs:132

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 crates/engine/src/finite_geometry_tests.rs | 40 ++++++++++++++++++++++
 crates/engine/src/lib.rs                   | 21 +++++++++++-
 2 files changed, 60 insertions(+), 1 deletion(-)
 create mode 100644 crates/engine/src/finite_geometry_tests.rs

diff --git a/crates/engine/src/finite_geometry_tests.rs b/crates/engine/src/finite_geometry_tests.rs
new file mode 100644
index 00000000..416b250c
--- /dev/null
+++ b/crates/engine/src/finite_geometry_tests.rs
@@ -0,0 +1,40 @@
+//! Commands never leave a layer with a non-finite position or size: such a file saves but can't be
+//! reopened (JSON writes NaN and infinity as null).
+
+use serde_json::json;
+
+use crate::Session;
+
+fn rect(s: &mut Session) -> crate::NodeId {
+    let r = s.execute("node.create", &json!({"type": "rectangle", "x": 0, "y": 10, "width": 100, "height": 50})).unwrap();
+    crate::params::id_of(&r["id"]).unwrap()
+}
+
+fn assert_roundtrips(s: &Session) {
+    let bytes = figcraft_format::save_bytes(s.doc().unwrap(), None).unwrap();
+    assert!(figcraft_format::load_bytes(&bytes).is_ok(), "the saved file reopens");
+}
+
+#[test]
+fn huge_moves_are_refused_and_the_file_still_reopens() {
+    let mut s = Session::new();
+    let r = rect(&mut s);
+    s.execute("transform.move", &json!({"ids": [r], "dx": 1e308, "dy": 0})).ok();
+    let second = s.execute("transform.move", &json!({"ids": [r], "dx": 1e308, "dy": 1e308}));
+    assert!(second.is_err(), "a move past the f64 range is refused");
+    let n = s.doc().unwrap().node(r).unwrap();
+    assert!(n.transform.as_coeffs().iter().all(|c| c.is_finite()), "{:?}", n.transform);
+    assert_roundtrips(&s);
+}
+
+#[test]
+fn huge_scale_is_refused_and_the_file_still_reopens() {
+    let mut s = Session::new();
+    let r = rect(&mut s);
+    s.execute("transform.scale", &json!({"ids": [r], "factor": 1e300})).ok();
+    let second = s.execute("transform.scale", &json!({"ids": [r], "factor": 1e300}));
+    assert!(second.is_err(), "a size past the f64 range is refused");
+    let n = s.doc().unwrap().node(r).unwrap();
+    assert!(n.width.is_finite() && n.height.is_finite(), "{} x {}", n.width, n.height);
+    assert_roundtrips(&s);
+}
diff --git a/crates/engine/src/lib.rs b/crates/engine/src/lib.rs
index 34653bd5..18498146 100644
--- a/crates/engine/src/lib.rs
+++ b/crates/engine/src/lib.rs
@@ -878,7 +878,8 @@ impl Session {
         let result = guard::run(id, || (spec.run)(self, params))
             .and_then(|v| self.check_instance_structure(id, &before).map(|()| v))
             .and_then(|v| self.check_preview(id, &before).map(|()| v))
-            .and_then(|v| self.check_live_access(id, &before).map(|()| v));
+            .and_then(|v| self.check_live_access(id, &before).map(|()| v))
+            .and_then(|v| self.check_finite_geometry(id, &before).map(|()| v));
         match &result {
             Ok(_) => {
                 self.after_command(spec, before);
@@ -916,6 +917,22 @@ impl Session {
         Err(EngineError::Disabled(id.to_string(), PREVIEW_READ_ONLY.into()))
     }
 
+    /// A layer's position and size stay finite: infinity and NaN are written as `null`, so a file
+    /// holding them saves but can't be reopened. Refuse such an edit (it is rolled back).
+    fn check_finite_geometry(&self, id: &str, before: &Option<(Arc<Document>, Vec<NodeId>, NodeId, u64)>) -> Result<()> {
+        let Some((bdoc, _, _, uid)) = before else { return Ok(()) };
+        let Some(ds) = self.docs.iter().find(|d| d.uid == *uid) else { return Ok(()) };
+        if Arc::ptr_eq(&ds.doc, bdoc) {
+            return Ok(());
+        }
+        let broken = |n: &Node| !(n.transform.as_coeffs().iter().all(|c| c.is_finite()) && n.width.is_finite() && n.height.is_finite());
+        let untouched = |n: &Node| bdoc.node_arc(n.id).zip(ds.doc.node_arc(n.id)).is_some_and(|(a, b)| Arc::ptr_eq(a, b));
+        match ds.doc.nodes().find(|n| broken(n) && !untouched(n)) {
+            Some(n) => Err(bad(id, format!("\"{}\" would get a position or size beyond the number range", n.name))),
+            None => Ok(()),
+        }
+    }
+
     /// A live session's document you may only view (or that is on its way to a server) is
     /// read-only: refuse an edit (it is rolled back).
     fn check_live_access(&self, id: &str, before: &Option<(Arc<Document>, Vec<NodeId>, NodeId, u64)>) -> Result<()> {
@@ -1528,6 +1545,8 @@ mod fig_export_tests;
 #[cfg(test)]
 mod fig_import_tests;
 #[cfg(test)]
+mod finite_geometry_tests;
+#[cfg(test)]
 mod frame_guides_tests;
 #[cfg(test)]
 mod frame_label_tests;