From 286d3de0aaf173bbe4fd712f515516b00f4f6892 Mon Sep 17 00:00:00 2001
From: NetterSilver <133535268+Silvertree2010@users.noreply.github.com>
Date: Mon, 19 Oct 2026 08:32:01 +0200
Subject: [PATCH] Drop minus sign from dimension text that rounds to zero
 (#1403)

Found while testing crates/render/src/units.rs:139-160 (format_linear, unit 3 and 4 arms) and feet_inches at :101

Co-authored-by: Claude Haiku 5.5 <noreply@anthropic.com>
---
 crates/render/src/units.rs | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/crates/render/src/units.rs b/crates/render/src/units.rs
index 61f616ec..f3d429c6 100644
--- a/crates/render/src/units.rs
+++ b/crates/render/src/units.rs
@@ -102,7 +102,8 @@ fn feet_inches(neg: bool, ft: i64, inch_plain: &str, inch_m: &str, inch_zero: bo
     let mode = zin & 3;
     let show_ft = ft != 0 || mode == 1 || mode == 2;
     let show_in = !inch_zero || mode == 1 || mode == 3 || (ft == 0 && !show_ft);
-    let sign = if neg { "-" } else { "" };
+    // A negative value that rounds to zero prints without a sign.
+    let sign = if neg && (ft != 0 || !inch_zero) { "-" } else { "" };
     let mut p = String::from(sign);
     let mut m = String::from(sign);
     if show_ft {
@@ -282,6 +283,39 @@ mod tests {
         assert_eq!(format_linear(0.4, &f(5, 2, 0)).0, "1/2");
     }
 
+    #[test]
+    fn negative_values_rounding_to_zero_have_no_sign() {
+        for unit in 1..=5 {
+            for decimals in [0, 2, 4] {
+                for zin in [0, 1] {
+                    for v in [-1e-9, -0.0] {
+                        let (p, m) = format_linear(v, &f(unit, decimals, zin));
+                        assert!(!p.starts_with('-') || unit == 1 && v != 0.0, "unit {unit} decimals {decimals} zin {zin}: {p}");
+                        assert!(!m.starts_with('-') || unit == 1 && v != 0.0, "unit {unit} decimals {decimals} zin {zin}: {m}");
+                    }
+                }
+            }
+        }
+        // DIMRND rounding a small negative value to zero, in every unit.
+        for unit in 1..=5 {
+            let mut c = f(unit, 4, 0);
+            c.round = 0.25;
+            let (p, m) = format_linear(-0.1, &c);
+            assert!(!p.starts_with('-') && !m.starts_with('-'), "unit {unit} with DIMRND: {p} / {m}");
+        }
+        assert_eq!(format_linear(-1e-9, &f(4, 4, 0)).0, "0\"");
+        assert_eq!(format_linear(-1e-9, &f(3, 4, 0)).0, "0.0000\"");
+        // Scientific keeps the sign: the mantissa of a tiny negative value is not zero.
+        assert_eq!(format_linear(-1e-9, &f(1, 2, 0)).0, "-1.00E-09");
+        // The shared feet/inch joiner never signs an all-zero result.
+        assert_eq!(feet_inches(true, 0, "0", "0", true, 0).0, "0\"");
+        assert_eq!(feet_inches(true, 0, "0", "0", true, 1).0, "0'-0\"");
+        // Genuinely negative values keep the sign.
+        assert_eq!(format_linear(-18.5, &f(4, 4, 0)).0, "-1'-6 1/2\"");
+        assert_eq!(format_linear(-18.5, &f(3, 2, 0)).0, "-1'-6.50\"");
+        assert_eq!(format_linear(-24.0, &f(4, 4, 0)).0, "-2'");
+    }
+
     #[test]
     fn angles() {
         assert_eq!(format_angle(std::f64::consts::FRAC_PI_4, 0, 0, 0), "45°");