From 2e03e178204ac9cc483140d3b8d9e5683a46911e Mon Sep 17 00:00:00 2001
From: Nigel Ihza Firdausy <106657905+Ni-zav@users.noreply.github.com>
Date: Sat, 10 Oct 2026 15:52:05 +0700
Subject: [PATCH] fix(layout): reject unsupported spread-view rotation angles

Reject non-quarter-turn or non-integer view angles instead of silently
truncating or defaulting them. Add a command-level regression test for
invalid inputs, valid quarter turns, and clearing the rotation.
---
 crates/engine/src/cmd/layout.rs | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/crates/engine/src/cmd/layout.rs b/crates/engine/src/cmd/layout.rs
index bd532079..bf967483 100644
--- a/crates/engine/src/cmd/layout.rs
+++ b/crates/engine/src/cmd/layout.rs
@@ -105,7 +105,13 @@ pub fn specs() -> Vec<CommandSpec> {
             has_doc,
             |s, p| {
                 let si = p.get("spread").and_then(Value::as_u64).unwrap_or(0) as usize;
-                let angle = p.get("angle").and_then(Value::as_i64).unwrap_or(90);
+                let angle = match p.get("angle") {
+                    None => 90,
+                    Some(v) => v.as_i64().ok_or_else(|| bad("layout.rotateSpreadView", "angle must be an integer multiple of 90 degrees"))?,
+                };
+                if angle % 90 != 0 {
+                    return Err(bad("layout.rotateSpreadView", "angle must be an integer multiple of 90 degrees"));
+                }
                 s.edit(|d, _| {
                     let sp = d.spreads.get_mut(si).ok_or_else(|| bad("layout.rotateSpreadView", "no such spread"))?;
                     let pg = std::sync::Arc::make_mut(sp).pages.first_mut().ok_or_else(|| bad("layout.rotateSpreadView", "empty spread"))?;
@@ -921,3 +927,27 @@ mod adjust_tests {
         assert_eq!(b, b2);
     }
 }
+
+#[cfg(test)]
+mod spread_rotation_input_tests {
+    use serde_json::json;
+
+    #[test]
+    fn quarter_turns_work_and_other_angles_are_rejected_without_mutation() {
+        let mut s = crate::Session::new();
+        s.execute("file.new", &json!({})).unwrap();
+        let rotation = |s: &crate::Session| s.doc().unwrap().doc.spreads[0].pages[0].view_rotation;
+        for bad in [json!(45), json!(-45), json!(91), json!("90"), json!(0.5)] {
+            assert!(s.execute("layout.rotateSpreadView", &json!({"angle": bad})).is_err(), "{bad}");
+            assert_eq!(rotation(&s), 0, "invalid input must not change the view");
+        }
+        s.execute("layout.rotateSpreadView", &json!({"angle": 90})).unwrap();
+        assert_eq!(rotation(&s), 1);
+        s.execute("layout.rotateSpreadView", &json!({"angle": -90})).unwrap();
+        assert_eq!(rotation(&s), 0);
+        s.execute("layout.rotateSpreadView", &json!({"angle": 180})).unwrap();
+        assert_eq!(rotation(&s), 2);
+        s.execute("layout.rotateSpreadView", &json!({"angle": 0})).unwrap();
+        assert_eq!(rotation(&s), 0, "zero resets the spread view");
+    }
+}