fix(print): a printed page's form shares the page's Resources when it adds no appearance (#6089)

crates/print/src/imposition.rs

@@ -219,14 +219,22 @@ pub(crate) fn page_form(
         body.extend(format!("q {} {} {} {} {} {} cm /{name} Do Q\n", n(a0), n(b0), n(c0), n(d0), n(e0), n(f0)).bytes());
         xobjects.set(name.into_bytes(), Object::Ref(ap));
     }
-    if !xobjects.is_empty() {
-        res.set(b"XObject".to_vec(), Object::Dict(xobjects));
-    }
+    // With no appearance added the form keeps the page's own Resources, shared by reference,
+    // rather than a deep copy per printed page.
+    let resources = match page.dict.get(b"Resources") {
+        Some(r) if k == 0 && doc.resolve(r).as_dict().is_some() => r.clone(),
+        _ => {
+            if !xobjects.is_empty() {
+                res.set(b"XObject".to_vec(), Object::Dict(xobjects));
+            }
+            Object::Dict(res)
+        }
+    };
     let mut d = Dict::new();
     d.set(b"Type".to_vec(), Object::name("XObject"));
     d.set(b"Subtype".to_vec(), Object::name("Form"));
     d.set(b"BBox".to_vec(), Object::Array(crop.iter().map(|v| Object::Real(*v)).collect()));
-    d.set(b"Resources".to_vec(), Object::Dict(res));
+    d.set(b"Resources".to_vec(), resources);
     if let Some(g) = page.dict.get(b"Group") {
         d.set(b"Group".to_vec(), g.clone());
     }

crates/print/src/tests.rs

@@ -1285,3 +1285,15 @@ fn contents_pieces_join_with_a_space_across_a_trailing_comment() {
     let printed_ctrl = impose(&with_newline, &settings(vec![0], Layout::Size(SizeMode::Actual))).unwrap();
     assert_eq!(form_strings(printed_ctrl), [b"HIDDEN".to_vec(), b"SHOWN".to_vec()]);
 }
+
+#[test]
+fn a_page_form_without_annotations_shares_the_pages_indirect_resources() {
+    let mut doc = fixture(2);
+    let pages = pdfcraft_model::pages(&doc);
+    let res = doc.add(Object::Dict([(b"Font".to_vec(), Object::Dict(Dict::new()))].into_iter().collect()));
+    doc.update_dict(pages[1].obj, |d| d.set(b"Resources".to_vec(), Object::Ref(res))).unwrap();
+    let pages = pdfcraft_model::pages(&doc);
+    let form = imposition::page_form(&mut doc, &pages, 1, Content::default(), &mut Default::default()).unwrap();
+    let Object::Stream(s) = &*doc.get(form) else { panic!("form stream") };
+    assert_eq!(s.dict.get(b"Resources"), Some(&Object::Ref(res)));
+}