From 754841aaa45947fb1b059f534ef4634cd0fc9841 Mon Sep 17 00:00:00 2001
From: Brandon Thomas <echelon@gmail.com>
Date: Tue, 13 Oct 2026 06:39:06 -0400
Subject: [PATCH] Pptx: a table naming no style reads as the table grid style

A table whose tblPr names no tableStyleId drew without any lines.
PowerPoint draws such a table with thin dark grid lines (as its "No Style,
Table Grid"); observed on a synthetic deck with and without the explicit
"No Style, No Grid" GUID. Such tables now read as the grid style.

Wild synthetic set: tables with cell margins/fills/styles 4.80 -> 2.82,
11.28 -> 10.15, 6.86 -> 3.16.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
---
 crates/pptx/src/read/shapes.rs |  4 +++-
 crates/pptx/tests/fills.rs     | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/crates/pptx/src/read/shapes.rs b/crates/pptx/src/read/shapes.rs
index 51b2b86..c4b3f77 100644
--- a/crates/pptx/src/read/shapes.rs
+++ b/crates/pptx/src/read/shapes.rs
@@ -436,7 +436,9 @@ fn smartart(imp: &mut Imp, part: &Part, gd: &El, frame: &Shape, depth: usize) ->
 }
 
 fn table(imp: &mut Imp, part: &Part, tbl: &El) -> Table {
-    let mut t = Table { style: "none".into(), first_row: false, band_row: false, ..Default::default() };
+    // A table naming no style is drawn by PowerPoint with thin dark grid lines ("No Style, Table
+    // Grid"), not without lines.
+    let mut t = Table { style: "grid".into(), first_row: false, band_row: false, ..Default::default() };
     if let Some(pr) = tbl.child("tblPr") {
         t.background = pr.elements().find(|e| e.local().ends_with("Fill") && e.local() != "noFill").and_then(|f| dml::fill_el(imp, part, f));
         t.first_row = pr.bool("firstRow").unwrap_or(false);
diff --git a/crates/pptx/tests/fills.rs b/crates/pptx/tests/fills.rs
index 8620b76..77e719e 100644
--- a/crates/pptx/tests/fills.rs
+++ b/crates/pptx/tests/fills.rs
@@ -170,3 +170,36 @@ fn a_gradient_tile_rect_is_read_and_round_trips() {
     let s = q.slides[0].shapes.iter().find(|s| s.name == "Corner").expect("shape");
     assert!(matches!(&s.fill, Some(Fill::Gradient(g)) if g.tile == [-1.0, -1.0, 0.0, 0.0]), "{:?}", s.fill);
 }
+
+#[test]
+fn a_table_naming_no_style_is_drawn_with_the_table_grid() {
+    let mut p = defaults::new_presentation(None);
+    let id = ShapeId(p.alloc_id());
+    let first = p.slides[0].id;
+    let mut t = deckcraft_model::Table::new(2, 2, 200.0, 40.0);
+    t.style = "none".into();
+    p.slide_mut(first).expect("slide").shapes.push(Shape {
+        id,
+        name: "Grid".into(),
+        xfrm: Some(Xfrm::new(10.0, 10.0, 200.0, 80.0)),
+        kind: deckcraft_model::ShapeKind::Table(t),
+        ..Default::default()
+    });
+    let bytes = deckcraft_pptx::export(&p).expect("export");
+    let style = |bytes: &[u8]| {
+        let q = deckcraft_pptx::import(bytes).expect("import");
+        let s = q.slides[0].shapes.iter().find(|s| s.name == "Grid").expect("shape").clone();
+        match s.kind {
+            deckcraft_model::ShapeKind::Table(t) => t.style,
+            other => panic!("{other:?}"),
+        }
+    };
+    // Written with its style, it reads back as written.
+    assert_eq!(style(&bytes), "none");
+    // Without a:tableStyleId PowerPoint draws thin dark grid lines.
+    let bare = edit_slides(&bytes, |x| {
+        let (Some(a), Some(b)) = (x.find("<a:tableStyleId>"), x.find("</a:tableStyleId>")) else { return x };
+        format!("{}{}", &x[..a], &x[b + "</a:tableStyleId>".len()..])
+    });
+    assert_eq!(style(&bare), "grid");
+}