From 6b7abc61d117278162c173b250a44ac7ee16159d Mon Sep 17 00:00:00 2001
From: mtlcl410 <hpcgrid@gmail.com>
Date: Thu, 15 Oct 2026 14:30:42 +0800
Subject: [PATCH] fix(edit): flattening keeps a widget it cannot draw and an
 undrawn reply (#1794) (#1934)

A widget with no appearance to draw (none stored, or none for its selected
state) was removed from the page and the field tree with nothing in its
place, so the field's value was lost; a reply kept because it could not be
drawn was then deleted anyway as a reply of the flattened comment. Both now
stay as they are. A widget whose appearance draws nothing is still removed,
as is a reply note's empty appearance with its comment.


Claude-Session: https://claude.ai/code/session_01RUNQSPVXx3dDBabRZHAnjz

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>
---
 crates/edit/src/flatten.rs   | 26 ++++++++++++++----
 crates/edit/src/tests.rs     | 52 ++++++++++++++++++++++++++++++++++++
 parity/acrobat-features.toml |  8 +++---
 3 files changed, 77 insertions(+), 9 deletions(-)

diff --git a/crates/edit/src/flatten.rs b/crates/edit/src/flatten.rs
index a3f6c886a2..8202c18d83 100644
--- a/crates/edit/src/flatten.rs
+++ b/crates/edit/src/flatten.rs
@@ -6,7 +6,8 @@
 //! the appearance's bounding box, transformed by its `/Matrix`, mapped onto `/Rect`). Hidden
 //! annotations are left alone; links are kept (they have no ink and stay clickable). Flattened
 //! comments take their pop-ups and replies with them; flattened widgets are removed from the
-//! form's field tree.
+//! form's field tree. An annotation whose appearance cannot be drawn is not flattened: it stays
+//! as it is, so no comment or field value is lost with nothing in its place.
 
 use std::collections::HashSet;
 
@@ -154,6 +155,8 @@ fn flatten_which(doc: &mut Document, pages: &[usize], which: Which) -> Result<us
             .unwrap_or_default();
         let mut gone: HashSet<ObjRef> = HashSet::new();
         let mut gone_inline: HashSet<usize> = HashSet::new();
+        // Selected, but nothing was drawn for it: it stays, pop-up and reply handling included.
+        let mut undrawn: HashSet<ObjRef> = HashSet::new();
         // A viewer draws many comments from their dictionary even when the file stores no
         // appearance (notes, FreeText, ink, stamps…). Build the appearance it would show, so
         // flattening keeps a comment that still has ink on screen instead of deleting it.
@@ -199,9 +202,18 @@ fn flatten_which(doc: &mut Document, pages: &[usize], which: Which) -> Result<us
             }
             // A comment whose ink was not written into the page stays. Removing it would drop
             // the annotation (a cloudy square this builder cannot draw, for example) with nothing
-            // left on the page. Widgets are form fields: flattening still removes them.
-            if !widget && !drew {
-                continue;
+            // left on the page. A widget stays when it has no appearance to draw at all (none
+            // stored, or none for its selected state): removing it would lose the field's value
+            // with nothing in its place (#1794). One whose appearance draws nothing (an empty
+            // stream) shows nothing anywhere, so flattening still removes it.
+            if !drew {
+                let no_appearance = appearance(doc, d).is_none();
+                if no_appearance && let Some(r) = entry.as_ref() {
+                    undrawn.insert(r);
+                }
+                if !widget || no_appearance {
+                    continue;
+                }
             }
             match entry.as_ref() {
                 Some(r) => {
@@ -218,9 +230,13 @@ fn flatten_which(doc: &mut Document, pages: &[usize], which: Which) -> Result<us
         if gone.is_empty() && gone_inline.is_empty() {
             continue;
         }
-        // Pop-ups and replies of what was flattened go too.
+        // Pop-ups and replies of what was flattened go too, except a reply that stayed because
+        // it could not be drawn: its content would go with nothing in its place.
         for entry in &list {
             let Some(r) = entry.as_ref() else { continue };
+            if undrawn.contains(&r) {
+                continue;
+            }
             let obj = doc.get(r);
             let Some(d) = obj.as_dict() else { continue };
             let points_at = |k: &[u8]| d.reference(k).is_some_and(|t| gone.contains(&t));
diff --git a/crates/edit/src/tests.rs b/crates/edit/src/tests.rs
index 912cb3c904..6df0ce21ea 100644
--- a/crates/edit/src/tests.rs
+++ b/crates/edit/src/tests.rs
@@ -294,6 +294,58 @@ fn flattening_fields_drops_the_ones_on_no_page() {
     assert_eq!(left, [pdfcraft_cos::ObjRef::new(7, 0)], "only the hidden field on the page stays");
 }
 
+/// #1794: a form field whose widget has no usable appearance (none stored, or none for its
+/// selected state) has nothing to draw. Flattening used to remove it anyway, losing its value
+/// with no ink in its place. It stays, in the page and in the form, like a comment that can't be
+/// drawn; a field with an appearance is still baked in and removed.
+#[test]
+fn flattening_keeps_a_valued_widget_it_cannot_draw() {
+    let page = stream("", " ");
+    let mut doc = build(&[
+        "<< /Type /Catalog /Pages 2 0 R /AcroForm << /Fields [5 0 R 6 0 R 7 0 R] >> >>",
+        "<< /Type /Pages /Kids [3 0 R] /Count 1 >>",
+        "<< /Type /Page /Parent 2 0 R /MediaBox [0 0 200 200] /Resources << >> /Contents 4 0 R /Annots [5 0 R 6 0 R 7 0 R] >>",
+        &page,
+        "<< /Type /Annot /Subtype /Widget /FT /Tx /T (name) /V (Ada) /Rect [10 10 150 40] /F 4 >>",
+        "<< /Type /Annot /Subtype /Widget /FT /Btn /T (agree) /V /Yes /AS /Yes /Rect [10 50 30 70] /F 4 /AP << /N << /Off 8 0 R >> >> >>",
+        "<< /Type /Annot /Subtype /Widget /FT /Tx /T (drawn) /V (Bob) /Rect [10 90 150 120] /F 4 /AP << /N 8 0 R >> >>",
+        "<< /Type /XObject /Subtype /Form /BBox [0 0 140 30] /Length 0 >>\nstream\n\nendstream",
+    ]);
+    assert_eq!(flatten(&mut doc, &[0], false, true).unwrap(), 1, "only the field with an appearance is drawn");
+    let doc = reopen(&doc);
+    let refs = |o: &Object| -> Vec<u32> { doc.resolve(o).as_array().unwrap().iter().filter_map(|f| f.as_ref()).map(|r| r.num).collect() };
+    let p = &pdfcraft_model::pages(&doc)[0];
+    assert_eq!(refs(p.dict.get(b"Annots").unwrap()), [5, 6], "the undrawable widgets stay on the page");
+    let root = doc.root().unwrap();
+    let af = doc.resolve(doc.get(root).as_dict().unwrap().get(b"AcroForm").unwrap());
+    assert_eq!(refs(af.as_dict().unwrap().get(b"Fields").unwrap()), [5, 6], "and in the form");
+    let value = |n: u32| doc.get(pdfcraft_cos::ObjRef::new(n, 0)).as_dict().unwrap().get(b"V").cloned();
+    assert_eq!(value(5), Some(Object::String(pdfcraft_cos::PdfString::literal(b"Ada".to_vec()))));
+    assert_eq!(value(6), Some(Object::name("Yes")));
+}
+
+/// #1794: a reply this builder cannot draw stays on the page even when the comment it replies to
+/// is flattened; the comment's pop-up still goes with it.
+#[test]
+fn flattening_keeps_an_undrawn_reply_to_a_flattened_comment() {
+    let page = stream("", " ");
+    let mut doc = build(&[
+        "<< /Type /Catalog /Pages 2 0 R >>",
+        "<< /Type /Pages /Kids [3 0 R] /Count 1 >>",
+        "<< /Type /Page /Parent 2 0 R /MediaBox [0 0 600 800] /Resources << >> /Contents 4 0 R /Annots [5 0 R 6 0 R 7 0 R] >>",
+        &page,
+        "<< /Type /Annot /Subtype /Square /Rect [100 600 200 650] /C [1 0 0] /Contents (Synthetic comment) /AP << /N 8 0 R >> /Popup 7 0 R >>",
+        "<< /Type /Annot /Subtype /Square /Rect [100 500 200 550] /C [1 0 0] /Contents (Synthetic reply) /BE << /S /C /I 2 >> /IRT 5 0 R >>",
+        "<< /Type /Annot /Subtype /Popup /Rect [300 600 400 700] /Parent 5 0 R >>",
+        "<< /Type /XObject /Subtype /Form /BBox [100 600 200 650] /Length 28 >>\nstream\n1 0 0 RG 100 600 100 50 re S\nendstream",
+    ]);
+    assert_eq!(flatten(&mut doc, &[0], true, false).unwrap(), 1, "the comment is drawn; the cloudy reply cannot be");
+    let doc = reopen(&doc);
+    let p = &pdfcraft_model::pages(&doc)[0];
+    let left: Vec<u32> = doc.resolve(p.dict.get(b"Annots").unwrap()).as_array().unwrap().iter().filter_map(|f| f.as_ref()).map(|r| r.num).collect();
+    assert_eq!(left, [6], "the undrawn reply stays; the comment and its pop-up are gone");
+}
+
 /// Flattening never makes a `?` permanent: it refuses, changing nothing, a text box without an
 /// appearance whose text Helvetica can't draw (another program's), and a comment or form field
 /// whose appearance PdfCraft drew with `?` (marked `PCUndrawn`). A comment another program drew
diff --git a/parity/acrobat-features.toml b/parity/acrobat-features.toml
index e270a8f211..ad291ef2e1 100644
--- a/parity/acrobat-features.toml
+++ b/parity/acrobat-features.toml
@@ -4196,8 +4196,8 @@ milestone = "M5"
 status = "shipped"
 commands = ["comment.flatten"]
 tools = ["doc_flatten"]
-evidence = ["crates/edit/src/tests.rs::flattening_draws_appearances_into_the_page_and_removes_the_comments", "crates/engine/src/tests.rs::flattening_keeps_the_look_and_drops_the_objects", "crates/automation/tests/automation.rs::flattening_through_tools"]
-notes = "appearances become page content; pop-ups and replies removed"
+evidence = ["crates/edit/src/tests.rs::flattening_draws_appearances_into_the_page_and_removes_the_comments", "crates/edit/src/tests.rs::flattening_keeps_an_undrawn_reply_to_a_flattened_comment", "crates/engine/src/tests.rs::flattening_keeps_the_look_and_drops_the_objects", "crates/automation/tests/automation.rs::flattening_through_tools"]
+notes = "appearances become page content; pop-ups and replies removed; a comment or reply whose appearance cannot be drawn (a cloudy border, an unsupported subtype) stays as it is instead of being deleted"
 
 [[feature]]
 id = "comment.migrate"
@@ -4716,8 +4716,8 @@ milestone = "M6"
 status = "shipped"
 commands = ["form.flatten"]
 tools = ["doc_flatten"]
-evidence = ["crates/edit/src/tests.rs::flattening_draws_appearances_into_the_page_and_removes_the_comments", "crates/engine/src/tests.rs::flattening_keeps_the_look_and_drops_the_objects", "crates/automation/tests/automation.rs::flattening_through_tools"]
-notes = "widgets drawn into content and pruned from the field tree"
+evidence = ["crates/edit/src/tests.rs::flattening_draws_appearances_into_the_page_and_removes_the_comments", "crates/edit/src/tests.rs::flattening_keeps_a_valued_widget_it_cannot_draw", "crates/engine/src/tests.rs::flattening_keeps_the_look_and_drops_the_objects", "crates/automation/tests/automation.rs::flattening_through_tools"]
+notes = "widgets drawn into content and pruned from the field tree; a widget with no appearance to draw (none stored, or none for its selected state) stays a live field rather than losing its value, so a form with such fields is not fully flattened — Acrobat regenerates appearances first, which PdfCraft does not yet do here"
 
 [[feature]]
 id = "form.prepare-form-mode"