fix(pptx): round hard-break seats per line

assets/bugfixes/issue-1252/layout-audit.json

@@ -0,0 +1,157 @@
+{
+ "pages": [
+  {
+   "lines": {
+    "gt": 10,
+    "out": 10,
+    "matched": 10,
+    "missing": 0,
+    "extra": 0,
+    "deviant": 0,
+    "missing_text": [],
+    "extra_text": []
+   },
+   "baseline": {
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+    "worst_dy": 0.07998999999998091,
+    "worst_dy_signed": -0.07998999999998091,
+    "worst_line": "Hxg20-1"
+   },
+   "dx0": {
+    "mean_abs": 0.0,
+    "worst": 0.0
+   },
+   "width": {
+    "mean_abs_pct": 0.0724474522534723,
+    "worst_pct": 0.16320951942667283
+   },
+   "instances": {
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+    "large_shifts": [],
+    "fine_shift_threshold": 0.12,
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+    "fine_shifts": []
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+    "mismatches": [],
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+    "unmatched_hidden_out": 0,
+    "unmatched_hidden_gt_text": [],
+    "unmatched_hidden_out_text": []
+   },
+   "visible_fills": {
+    "mismatch_count": 0,
+    "mismatches": []
+   },
+   "pitch": {
+    "pairs": 9,
+    "worst_delta": 0.11998999999997295
+   },
+   "wraps": {
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+    "samples": []
+   },
+   "topology": {
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+    "gt_lines": 0,
+    "out_lines": 0,
+    "samples": []
+   },
+   "reflow": {
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+    "out_lines": 0,
+    "samples": []
+   },
+   "rects": {
+    "gt_count": 2,
+    "out_count": 1,
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+    "canonical_out_count": 1,
+    "matched": 1,
+    "unmatched_gt": 1,
+    "unmatched_out": 0,
+    "mean_center_delta": 3.25962899694332e-06,
+    "geometry_threshold": 0.12,
+    "geometry_mismatch_count": 0,
+    "geometry_mismatch_samples": [],
+    "samples": [
+     {
+      "kind": "fill",
+      "geometry_kind": "rectangle",
+      "gt_indices": [
+       1
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+      "gt_bbox": [
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+       200.0,
+       249.999993480742
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+       200.0,
+       250.0
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+      "dx": 0.0,
+      "dy": 0.0,
+      "dwidth": 0.0,
+      "dheight": 6.51925799388664e-06,
+      "edges": {
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+       "top": 0.0,
+       "right": 0.0,
+       "bottom": 6.51925799388664e-06
+      },
+      "center_dx": 0.0,
+      "center_dy": 3.25962899694332e-06,
+      "max_abs_delta": 6.51925799388664e-06
+     }
+    ],
+    "x": {
+     "mean_abs": 0.0,
+     "worst": 0.0
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+     "worst": 0.0
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+    "width": {
+     "mean_abs": 0.0,
+     "worst": 0.0
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+    "height": {
+     "mean_abs": 6.51925799388664e-06,
+     "worst": 6.51925799388664e-06
+    },
+    "edges": {
+     "left": {
+      "mean_abs": 0.0,
+      "worst": 0.0
+     },
+     "top": {
+      "mean_abs": 0.0,
+      "worst": 0.0
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+     "right": {
+      "mean_abs": 0.0,
+      "worst": 0.0
+     },
+     "bottom": {
+      "mean_abs": 6.51925799388664e-06,
+      "worst": 6.51925799388664e-06
+     }
+    }
+   },
+   "noise_floor": 0.12
+  }
+ ],
+ "gt_pages": 1,
+ "out_pages": 1
+}

assets/bugfixes/issue-1252/render-clusters-page-1.json

@@ -0,0 +1,22 @@
+{
+  "clusters": [],
+  "dpi": 300,
+  "duplicate_disposition_cluster_ids": [],
+  "errors": [],
+  "fuzz_percent": 5,
+  "minimum_area_pt2": 20.0,
+  "page": 1,
+  "passed": true,
+  "renderer_observations": [],
+  "schema_version": 1,
+  "strict": true,
+  "summary": {
+    "dispositioned": 0,
+    "duplicate": 0,
+    "total": 0,
+    "undispositioned": 0,
+    "unknown": 0
+  },
+  "undispositioned_cluster_ids": [],
+  "unknown_disposition_cluster_ids": []
+}

crates/office2pdf/src/render/typst_gen_fixed_page_textbox_tests.rs

@@ -3116,9 +3116,10 @@ fn powerpoint_empty_boundary_breaks_do_not_move_a_centred_title() {
 /// the whole box — 12.00pt for 12.5pt over 10pt. A nine-line probe of the same
 /// pair paces it at 12.96pt and its 10pt-over-12.5pt partner at 14.04pt, where
 /// the whole-box reading gives 12.00 and 15.00; the two sum to `1.2 x 22.5`
-/// either way, so only the boundary between them was ever in question. The
-/// half-point tolerances below are what separates the two models, and the
-/// 0.36pt inside them is the paragraph-wide seat share tracked in #1252.
+/// either way, so only the boundary between them was ever in question. Each
+/// line now rounds its own seat (#1252); the half-point tolerances below allow
+/// the native export's per-baseline coordinate dither while still separating
+/// the two models.
 #[cfg(not(target_arch = "wasm32"))]
 #[test]
 fn powerpoint_hard_break_advance_clears_the_line_above_it() {
@@ -3184,8 +3185,8 @@ fn powerpoint_hard_break_advance_clears_the_line_above_it() {
     assert_eq!(baselines.len(), 3, "expected three lines: {baselines:?}");
     let (top_em, _) = crate::render::pdf::powerpoint_line_box_em(family)
         .expect("the Arial-compatible line metrics must resolve");
-    // The paragraph's largest size decides its line box, and PowerPoint seats
-    // the baseline a whole number of points below its top (issue #1074).
+    // PowerPoint seats the baseline a whole number of points below the first
+    // line's top (issue #1074).
     let expected_first_baseline = 72.0 + (top_em * 12.5).round();
     assert!(
         (baselines[0] - expected_first_baseline).abs() < 0.01,
@@ -4220,3 +4221,52 @@ fn a_hard_broken_slide_line_advances_by_its_own_font_size() {
         }
     }
 }
+
+/// A mixed-size hard-broken paragraph rounds the seat of every line at that
+/// line's own size, rather than rounding once at the paragraph maximum and
+/// rescaling the resulting ratio (#1252).
+///
+/// The native PowerPoint probe behind the issue measures the most visible
+/// Arial 20/10 transition at 14.88pt down and 21.12pt back up, which is the
+/// export's 0.24pt coordinate grid around this model's 15pt and 21pt. The
+/// paragraph-wide split emits 14.5pt and 21.5pt instead. The other families
+/// keep the regression tied to the shared line-box model rather than to one
+/// lucky Arial rounding boundary.
+#[cfg(not(target_arch = "wasm32"))]
+#[test]
+fn mixed_size_hard_breaks_round_each_lines_own_seat() {
+    for (family, sizes_pt) in [
+        ("Arial", [20.0_f64, 10.0, 20.0]),
+        ("Georgia", [20.0_f64, 10.0, 20.0]),
+        ("Verdana", [20.0_f64, 10.0, 20.0]),
+        ("Arial", [30.0_f64, 10.0, 30.0]),
+    ] {
+        let baselines = hard_broken_slide_baselines(family, &sizes_pt, true);
+        let (plain_ascent_em, _) = crate::render::pdf::powerpoint_line_box_em(family)
+            .unwrap_or_else(|| panic!("the {family} line metrics must resolve"));
+        let line_box_pt = |size_pt: f64| -> (f64, f64) {
+            let (top_em, bottom_em) =
+                powerpoint_percentage_line_box_em(plain_ascent_em, size_pt, 1.0);
+            (top_em * size_pt, bottom_em * size_pt)
+        };
+
+        for ((sizes, baselines), direction) in sizes_pt
+            .windows(2)
+            .zip(baselines.windows(2))
+            .zip(["down", "up"])
+        {
+            let (_, preceding_bottom_pt) = line_box_pt(sizes[0]);
+            let (following_top_pt, _) = line_box_pt(sizes[1]);
+            let expected_pt = preceding_bottom_pt + following_top_pt;
+            let actual_pt = baselines[1] - baselines[0];
+            assert!(
+                (actual_pt - expected_pt).abs() < 0.01,
+                "the {family} {direction} break from {}pt to {}pt must use each \
+                 line's independently rounded seat: expected {expected_pt}pt, \
+                 got {actual_pt}pt from {baselines:?}",
+                sizes[0],
+                sizes[1],
+            );
+        }
+    }
+}

crates/office2pdf/src/render/typst_gen_table_codegen_tests.rs

@@ -1618,9 +1618,8 @@ fn test_slide_table_cell_uses_the_powerpoint_line_box() {
 /// every hard-broken line under 10pt at a flat 12.00pt (issue #1172). What
 /// actually carries the gap is the 13pt line's descent.
 ///
-/// The 0.37pt that remains is the paragraph-wide seat share, tracked in #1252;
-/// the tolerance here is the half point that separates a preceding line's
-/// descent from no descent at all.
+/// Each line now rounds its own seat (#1252), which predicts 11.60pt for this
+/// boundary and remains within the native export's half-point dither band.
 ///
 /// This compiles the real table-cell path so its vertical centring and line
 /// box cannot make a source-only assertion pass by accident (issue #683).
@@ -1702,10 +1701,21 @@ fn slide_table_hard_break_clears_the_taller_line_above_it() {
         .baseline_pt;
 
     let advance_pt: f64 = word_baseline - docx_baseline;
+    let (plain_ascent_em, _) = crate::render::pdf::powerpoint_line_box_em(family)
+        .expect("the Arial-compatible line metrics must resolve");
+    let line_box_pt = |size_pt: f64| -> (f64, f64) {
+        let (top_em, bottom_em) = powerpoint_percentage_line_box_em(plain_ascent_em, size_pt, 1.0);
+        (top_em * size_pt, bottom_em * size_pt)
+    };
+    let (_, docx_bottom_pt) = line_box_pt(13.0);
+    let (word_top_pt, _) = line_box_pt(9.5);
+    let expected_pt = docx_bottom_pt + word_top_pt;
     assert!(
-        advance_pt > 1.2 * 9.5 + 0.5,
-        "the 13pt line's descent must push the 9.5pt line past its own 11.4pt \
-         box: {docx_baseline}, {word_baseline}\n{}",
+        (advance_pt - expected_pt).abs() < 0.01,
+        "the break must combine the 13pt line's independently rounded descent \
+         with the 9.5pt line's independently rounded seat: expected \
+         {expected_pt}pt, got {advance_pt}pt from {docx_baseline}, \
+         {word_baseline}\n{}",
         output.source
     );
     assert!(