From 72a9e4456e4664266d81321115d901cd98445003 Mon Sep 17 00:00:00 2001
From: NetterSilver <133535268+Silvertree2010@users.noreply.github.com>
Date: Wed, 21 Oct 2026 03:34:30 +0000
Subject: [PATCH] Fix scientific number format for subnormal values

Found while testing crates/model/src/numfmt.rs:204-211 (sci)

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 crates/model/src/numfmt.rs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/crates/model/src/numfmt.rs b/crates/model/src/numfmt.rs
index c3cf1713..da2e2315 100644
--- a/crates/model/src/numfmt.rs
+++ b/crates/model/src/numfmt.rs
@@ -204,7 +204,12 @@ fn sci(toks: &[Tok], v: f64, sep: char, dec: char) -> Option<String> {
     let (mut m, mut exp) = (0.0, 0i32);
     if v != 0.0 {
         exp = v.log10().floor() as i32;
-        m = v / 10f64.powi(exp);
+        m = if exp < -300 {
+            // 10^exp underflows for subnormals; scale in two steps.
+            v * 1e300 / 10f64.powi(exp + 300)
+        } else {
+            v / 10f64.powi(exp)
+        };
         if !m.is_finite() {
             m = 0.0;
             exp = 0;
@@ -286,6 +291,12 @@ mod tests {
 
     const RUB: &str = r#"_-* #\ ##0\ "₽"_-;\-* #\ ##0\ "₽"_-;_-* "-"??\ "₽"_-;_-@_-"#;
 
+    #[test]
+    fn scientific_subnormal() {
+        assert_eq!(format("0.00E+00", 5e-324, None), "4.94E-324");
+        assert_eq!(format("0.00E+00", f64::MIN_POSITIVE, None), "2.23E-308");
+    }
+
     #[test]
     fn russian_accounting_roubles() {
         assert_eq!(format(RUB, 800_000.0, Some("ru-RU")), "800\u{a0}000 ₽");