Layout: align behind-text cell pictures (#1871) (#1871)

Co-authored-by: Brandon Thomas <echelon@gmail.com>

crates/layout/src/table.rs

@@ -673,10 +673,20 @@ pub fn layout_table(ctx: &mut Ctx, story: StoryRef, t: &Table, path: &[u32], ava
             {
                 items.push(Placed::Fill { rect, color: f });
             }
+            // Behind-text frames count towards vertical alignment even without inline content.
+            // They do not increase the row's flow height.
+            let align_h = c
+                .items
+                .iter()
+                .filter_map(|item| match item {
+                    Placed::Object { rect, wrap: wordcraft_doc::para::Wrap::BehindText, .. } => Some(rect.bottom()),
+                    _ => None,
+                })
+                .fold(c.h, f32::max);
             let mut dy = match c.valign {
                 VAlign::Top => 0.0,
-                VAlign::Center => ((span_h - c.h) / 2.0).max(0.0),
-                VAlign::Bottom => (span_h - c.h).max(0.0),
+                VAlign::Center => ((span_h - align_h) / 2.0).max(0.0),
+                VAlign::Bottom => (span_h - align_h).max(0.0),
             };
             let end = (c.vmerge != VMerge::Continue && c.turned.is_none()).then_some(c.end + dy);
             let mut cell_items = c.items;

crates/layout/src/tests.rs

@@ -7803,3 +7803,38 @@ fn kept_prefix_stays_together() {
     t.rows.insert(1, middle);
     assert_eq!(row_keep_pages(&d), [1, 1, 2], "an oversized follower cannot separate an already placed kept prefix");
 }
+
+/// Word and Adobe: a behind-text frame participates in a cell's vertical alignment,
+/// even when its anchor paragraph has no inline picture (synthetic two-cell probe).
+#[test]
+fn cell_frame_centres_empty() {
+    use wordcraft_doc::para::{Anchor, Float, Wrap};
+    use wordcraft_doc::props::{HeightRule, VAlign};
+    let mut d = Document::new();
+    let mut t = Table::new(1, 2, 468.0);
+    t.rows[0].props.height = Some(182.5);
+    t.rows[0].props.height_rule = HeightRule::Exact;
+    for (ci, cell) in t.rows[0].cells.iter_mut().enumerate() {
+        cell.props.valign = Some(VAlign::Center);
+        cell.props.margins = Some([0.0; 4]);
+        let mut p = wordcraft_doc::Paragraph::with_text("", Default::default());
+        p.props.space_before = Some(0.0);
+        p.props.space_after = Some(0.0);
+        let float = Float { wrap: Wrap::BehindText, h_rel: Anchor::Column, v_rel: Anchor::Paragraph, y: -12.75, ..Default::default() };
+        p.insert_object(0, picture(231.0, 180.75, float), &Default::default()).unwrap();
+        if ci == 0 {
+            p.insert_object(p.text.len(), picture(207.0, 155.25, Default::default()), &Default::default()).unwrap();
+        }
+        cell.blocks = vec![wordcraft_doc::para_block(p)];
+    }
+    d.insert_block(StoryRef::Body, &Path::top(0), wordcraft_doc::Block::Table(t)).unwrap();
+    let l = lay(&d);
+    let frames: Vec<_> = l.pages[0]
+        .items
+        .iter()
+        .filter_map(|item| if let Placed::Object { rect, wrap: Wrap::BehindText, .. } = item { Some(rect) } else { None })
+        .collect();
+    assert_eq!(frames.len(), 2);
+    assert!((frames[0].y - frames[1].y).abs() < 0.01, "frames must align: {frames:?}");
+    assert!((frames[0].y - 66.5).abs() < 0.5, "Word frame top: {frames:?}");
+}

docs/layout-parity.md

@@ -182,6 +182,9 @@ and save, in raster output and in PDF. Synthetic controls cover red rectangles,
 connectors. Custom lists are capped at 64 pairs; painted spans are bounded to 0.01–20000 pt.
 Theme-inherited dash styles, line caps, ink and open freeform strokes are not covered by this change.
 When content exceeds a preferred column width, AutoFit donors lose equal widths until they reach their content minima. Original synthetic Word probes cover donor reductions; cached field refresh and wrapping remain separate gaps.
+
+Behind-text pictures in table cells participate in centre and bottom vertical alignment without increasing row flow height.
+
 ## Revision history
 
 | Date | Change | Summary |
@@ -201,6 +204,7 @@ When content exceeds a preferred column width, AutoFit donors lose equal widths
 | 2026-10-16 | trivial | Hint-reliant CJK fonts execute TrueType contour assembly; Windows DFKai-SB no longer loses strokes. Synthetic local-font regression; no font binaries bundled. |
 | 2026-10-16 | trivial | `w:autoSpaceDE` and `w:autoSpaceDN` are laid out: a quarter em between Asian text and Latin text or digits (#2358) |
 | 2026-10-16 | trivial | AutoFit donors lose equal widths, bounded by content minima |
+| 2026-10-16 | trivial | Behind-text pictures in table cells participate in centre and bottom vertical alignment without increasing row flow height. |
 | 2026-10-14 | trivial | Row table border exceptions draw without leaking into other rows |
 | 2026-10-14 | trivial | Consistent cell widths override a stale table grid |
 | 2026-10-14 | trivial | Paragraphs inside complex-field instructions take no flow height; empty result paragraphs keep their line. |