Layout: exclude floating anchors from line font metrics (task 256) (#2462)

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

ROADMAP.md

@@ -165,6 +165,7 @@ Imported Word 97–2003 `.doc`/`.dot` files now ask for a supported DOCX target
 | 2026-10-14 | Tab stops edited on the ruler: the corner selector picks Left/Center/Right/Decimal/Bar, a click sets a stop (Alt skips the snap), dragging moves it with a guide line and position tooltip, dragging off the ruler clears it; markers draw per kind and mirror for RTL; one `para.tabs` call and one undo step per gesture |
 | 2026-10-12 | Fields keep `w:dirty` through DOCX saves (#877): a begin marker flagged by a generator that couldn't compute a result (pandoc-style TOC placeholders) keeps the flag on open/save — as a buffered field or a range field — so Word still refreshes it on open; computing a result (Update Field, Update Table) clears it, like Word's F9 |
 | 2026-10-15 | Exact line spacing keeps the run font baseline around tall equations; automatic and minimum spacing still grow for math. |
+| 2026-10-16 | Zero-extent drawing anchors contribute no inline font height. |
 |---|---|
 | 2026-10-15 | The font family caches are bounded (4096 families for text, 1024 for math, names over 256 bytes aren't remembered), so a document naming thousands of missing fonts can't grow memory; equation fonts are looked up again after a font is added or removed instead of keeping the old choice (#1354) |
 | 2026-10-15 | AutoCorrect recognizes `-->` as `→` (#2223), respecting replacement settings and undo without changing paragraph-start arrow bullets. |
@@ -512,6 +513,7 @@ Imported Word 97–2003 `.doc`/`.dot` files now ask for a supported DOCX target
 | 2026-10-14 | trivial | Progress log: Add Font imports every selected font file (#1789) |
 | 2026-10-15 | trivial | Additive paragraph spacing retains the full before-space after a section page break; ordinary overlapping spacing is unchanged. |
 | 2026-10-15 | trivial | Exact line spacing keeps the run font baseline around tall equations; automatic and minimum spacing still grow for math. |
+| 2026-10-16 | trivial | Zero-extent drawing anchors contribute no inline font height. Synthetic regressions. |
 | 2026-10-14 | trivial | Progress log: row table border exceptions |
 | 2026-10-12 | minor | Czech proofing review: short-word splits rank after deletion, NOSUGGEST excludes suggestions while accepting typed forms, affix comments apply only to headers, ratios keep spaces and repeated-word messages use Czech quotes; synthetic engine end-to-end and latency checks |
 | 2026-10-12 | minor | Czech spelling from the installed Hunspell dictionary, runtime-table suggestions and generic checks; Czech interface writes cs-CZ documents; no Czech hyphenation patterns bundled; estimates unchanged |

crates/layout/src/para.rs

@@ -2219,7 +2219,9 @@ fn break_lines(pl: &mut ParaLayout, env: &ParaEnv, mark_style: u32, level: Optio
             // Spaces and tabs never make a line taller, whatever their size: Word sizes a line by
             // its other characters (a line of only them takes the paragraph mark's), measured in
             // Word for Windows with 9 pt text and 11–20 pt tabs, spaces and ideographic spaces.
-            if matches!(c.kind, ClKind::Marker | ClKind::Space | ClKind::Tab) || c0 + k < dropped {
+            // Floating and hidden drawings have no inline extent; their anchor font takes no height.
+            let anchor = matches!(c.kind, ClKind::Object(_)) && c.adv == 0.0 && c.obj_h == 0.0;
+            if matches!(c.kind, ClKind::Marker | ClKind::Space | ClKind::Tab) || anchor || c0 + k < dropped {
                 continue;
             }
             if let Some(st) = pl.styles.get(c.style as usize) {

crates/layout/src/tests.rs

@@ -8223,3 +8223,26 @@ fn exact_math_keeps_run_baseline() {
         }
     }
 }
+
+#[test]
+fn float_font_keeps_line_height() {
+    use wordcraft_doc::CharProps;
+    use wordcraft_doc::para::{Float, Wrap};
+
+    let pitch = |wrap, size| {
+        let small = CharProps { size: Some(9.0), ..Default::default() };
+        let mut p = wordcraft_doc::Paragraph::with_text("Anchor", small.clone());
+        p.mark = small;
+        p.props.space_after = Some(0.0);
+        p.insert_object(0, picture(1.0, 1.0, Float { wrap, ..Default::default() }), &CharProps { size: Some(size), ..Default::default() }).unwrap();
+        let mut d = Document::from_text("After");
+        d.body.insert(0, wordcraft_doc::para_block(p));
+        let l = lay(&d);
+        l.caret(&Pos::body(1, 0)).unwrap().top - l.caret(&Pos::body(0, 0)).unwrap().top
+    };
+
+    for wrap in [Wrap::BehindText, Wrap::InFrontOfText] {
+        assert!((pitch(wrap, 40.0) - pitch(wrap, 9.0)).abs() < 0.01, "{wrap:?}");
+    }
+    assert!(pitch(Wrap::Inline, 40.0) > pitch(Wrap::Inline, 9.0));
+}

docs/gaps.md

@@ -117,6 +117,7 @@ The Language dialog reads effective character formatting, including document def
 | 2026-10-14 | trivial | #19 narrowed: ODT export done (master page and page layout per section, columned `text:section`s) |
 | 2026-10-15 | trivial | Additive paragraph spacing retains the full before-space after a section page break; ordinary overlapping spacing is unchanged. |
 | 2026-10-15 | trivial | Exact line spacing keeps the run font baseline around tall equations; automatic and minimum spacing still grow for math. |
+| 2026-10-16 | trivial | Zero-extent drawing anchors contribute no inline font height. Synthetic regressions. |
 | 2026-10-14 | trivial | Row table border exceptions fixed; other row table exceptions remain unsupported |
 | 2026-10-12 | minor | Czech proofing review: short-word splits rank after deletion, NOSUGGEST excludes suggestions while accepting typed forms, affix comments apply only to headers, ratios keep spaces and repeated-word messages use Czech quotes; synthetic engine end-to-end and latency checks |
 | 2026-10-12 | minor | Czech spelling from the installed Hunspell dictionary, runtime-table suggestions and generic checks; Czech interface writes cs-CZ documents; no Czech hyphenation patterns bundled; estimates unchanged |

docs/layout-parity.md

@@ -217,6 +217,7 @@ Behind-text pictures in table cells participate in centre and bottom vertical al
 | 2026-10-15 | trivial | Removed the 12 pt line-width floor in narrow cells and float spans; synthetic wrapping and oversized-glyph controls |
 | 2026-10-15 | trivial | Partial cell margins retain omitted edges through DOCX save and inherit current table defaults during layout. Original import/write and row-height regressions. |
 | 2026-10-15 | trivial | Exact line spacing keeps the run font baseline around tall equations; automatic and minimum spacing still grow for math. |
+| 2026-10-16 | trivial | Zero-extent drawing anchors contribute no inline font height. Synthetic regressions. |
 | 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. |