From 56adfd7809ff3920a3307aadc211c53c745dd2fd Mon Sep 17 00:00:00 2001
From: Eric Kaden <608341+EricKaden@users.noreply.github.com>
Date: Sat, 24 Oct 2026 15:34:00 -0400
Subject: [PATCH] M12: a radio button that must be chosen makes its group
 required even when an earlier button made the group

---
 crates/xfa/src/pdf.rs   | 12 +++++++++++-
 crates/xfa/src/tests.rs |  8 +++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/crates/xfa/src/pdf.rs b/crates/xfa/src/pdf.rs
index 259d3add51..5a831b07c9 100644
--- a/crates/xfa/src/pdf.rs
+++ b/crates/xfa/src/pdf.rs
@@ -497,7 +497,17 @@ impl Emitter<'_> {
             WidgetKind::Radio { group, on, .. } => {
                 top_level = false;
                 let parent = match self.radio_groups.get(group) {
-                    Some((p, _)) => *p,
+                    Some((p, _)) => {
+                        let p = *p;
+                        // A later button that must be chosen makes the group required too.
+                        if w.required {
+                            self.doc.update_dict(p, |g| {
+                                let ff = g.int(b"Ff").unwrap_or(0);
+                                g.set(b"Ff".to_vec(), Object::Int(ff | (1 << 1)));
+                            })?;
+                        }
+                        p
+                    }
                     None => {
                         let mut g = Dict::new();
                         g.set(b"FT".to_vec(), Object::name("Btn"));
diff --git a/crates/xfa/src/tests.rs b/crates/xfa/src/tests.rs
index 9175be703e..bfdffdcbc5 100644
--- a/crates/xfa/src/tests.rs
+++ b/crates/xfa/src/tests.rs
@@ -339,7 +339,8 @@ fn rendering_into_the_pdf_replaces_the_placeholder_page_and_adds_fields() {
 
 /// A field or exclusion group that must be filled in (`<validate nullTest="error">`) becomes a
 /// Required field, which viewers outline when they highlight a form's fields: a radio group on the
-/// group field, its buttons' flags being the group's. `nullTest="warning"` only recommends a value,
+/// group field, its buttons' flags being the group's (a button of its own that must be chosen
+/// makes the group required too). `nullTest="warning"` only recommends a value,
 /// so it, like no test, leaves the field optional.
 #[test]
 fn fields_that_must_be_filled_in_are_required() {
@@ -357,6 +358,10 @@ fn fields_that_must_be_filled_in_are_required() {
 <exclGroup name="optional" layout="lr-tb">
  <field name="a" w="1in" h="0.3in"><ui><checkButton shape="round"/></ui><items><text>A</text></items></field>
 </exclGroup>
+<exclGroup name="second" layout="lr-tb">
+ <field name="b" w="1in" h="0.3in"><ui><checkButton shape="round"/></ui><items><text>B</text></items></field>
+ <field name="c" w="1in" h="0.3in"><ui><checkButton shape="round"/></ui><items><text>C</text></items><validate nullTest="error"/></field>
+</exclGroup>
 </subform></template></xdp:xdp>"##;
     let mut doc = Document::open(Arc::new(shell(xdp))).unwrap();
     render_into(&mut doc).unwrap();
@@ -378,6 +383,7 @@ fn fields_that_must_be_filled_in_are_required() {
     assert_eq!(leaf("agree"), Some(true), "a check box too");
     assert_eq!(leaf("answer"), Some(true), "the radio group field");
     assert_eq!(leaf("optional"), Some(false));
+    assert_eq!(leaf("second"), Some(true), "a later button that must be chosen makes its group required");
 }
 
 /// A dynamic form's own text that the standard fonts can't draw is laid out anyway and reported