fix: a half-scrolled spreadsheet row draws its text cut at the body

A row partly under the header or past the bottom edge drew its zebra band
but no text until it was wholly inside, so scrolling rows arrived empty and
their values popped in a row late. The cells now draw with their bounds
clamped to the body band, which the glyph pass clips per pixel.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

 src/widget/container/spreadsheet.rs | 39 ++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/widget/container/spreadsheet.rs b/src/widget/container/spreadsheet.rs
index 1121a95..fc62711 100644
--- a/src/widget/container/spreadsheet.rs
+++ b/src/widget/container/spreadsheet.rs
@@ -459,7 +459,7 @@ impl Paint for Spreadsheet {
             );
         }
 
-        // Header + cell text. Cells render only when the row lies fully inside the body.
+        // Header + cell text, each cell clamped to its column and the body band.
         if self.headers.is_empty() {
             return;
         }
@@ -525,9 +525,15 @@ impl Paint for Spreadsheet {
             };
             ctx.text_with(fit(label), cx, y + 6.0, 12.0, color, None, col_bounds(i, y, HEADER_H));
         }
+        // A row half scrolled under the header or off the bottom draws its
+        // text CUT at the body band, as its zebra fill is. Until 2026-09-30
+        // it drew no text until it was wholly inside, so a scrolling row's
+        // band arrived empty and its values popped in a row's height late.
         for (i, &src) in self.order.iter().enumerate() {
             let ry = y + HEADER_H + i as f32 * ROW_H - scroll;
-            if ry < body_top || ry + ROW_H > body_bottom {
+            let top = ry.max(body_top);
+            let bottom = (ry + ROW_H).min(body_bottom);
+            if bottom <= top {
                 continue;
             }
             for (col_idx, val) in self.rows[src].iter().enumerate().take(n_cols) {
@@ -535,7 +541,7 @@ impl Paint for Spreadsheet {
                     continue;
                 }
                 let cx = xoff + col_w * col_idx as f32 + 8.0;
-                ctx.text_with(fit(val.clone()), cx, ry + 6.0, 12.0, [0xbb, 0xbb, 0xcc], None, col_bounds(col_idx, ry, ROW_H));
+                ctx.text_with(fit(val.clone()), cx, ry + 6.0, 12.0, [0xbb, 0xbb, 0xcc], None, col_bounds(col_idx, top, bottom - top));
             }
         }
     }
@@ -845,6 +851,33 @@ mod tests {
         s
     }
 
+    /// A row half scrolled out at either edge of the body draws its text cut
+    /// at the band — it used to draw none until it was wholly inside.
+    #[test]
+    fn a_half_scrolled_row_draws_its_text_cut_at_the_body() {
+        let rect = Rect { x: 0.0, y: 0.0, width: 200.0, height: 124.0 };
+        let mut s = filled(20);
+        (*s).scroll_y = ROW_H * 0.5;
+        let mut pc = crate::scene::paint::PaintCtx::new();
+        Paint::paint(&*s, rect, &mut pc);
+        let items = pc.finish().items;
+        let cell = |want: &str| {
+            items.iter().find_map(|item| match &item.prim {
+                crate::scene::paint::Prim::Text { text, bounds, .. } if text == want => *bounds,
+                _ => None,
+            })
+        };
+        let body_top = HEADER_H;
+        let body_bottom = rect.height;
+        // r0 spans -12..12 of the body; r4 runs 12 px past its bottom.
+        let top = cell("r0").expect("the row under the header draws its text");
+        assert_eq!((top[1], top[3]), (body_top, body_top + ROW_H * 0.5), "cut at the header");
+        let bottom = cell("r4").expect("the row off the bottom draws its text");
+        assert_eq!(bottom[3], body_bottom, "cut at the pane's bottom");
+        assert!(bottom[1] < bottom[3]);
+        assert!(cell("r5").is_none(), "a row wholly out of the body draws nothing");
+    }
+
     /// Columns floor at MIN_COL_W instead of squeezing: past the floor the run
     /// overflows into the horizontal scroll, and within it there is none.
     #[test]