Numeric fields: a decimal comma works in arithmetic next to a number with a point (#5684)

A numeric field read a comma as a decimal point only when the text had no
point at all. A field shows its value with a point (100.5 pt), so typing
-20,5 after it gave 100.5 pt-20,5, which kept its comma and was refused.

Each number now reads its own separator: commas become points unless the
text reads as thousands (1,000, as before). A number written with both
separators (1.234,5, 1,000.5) ends up with two points and is still refused
rather than guessed at.

crates/ui-egui/src/panels/tests_constrain.rs

@@ -256,6 +256,21 @@ fn a_thousands_comma_in_a_percentage_is_refused_in_a_size_field() {
     }
 }
 
+/// Arithmetic with a decimal comma works in W (#5684), also after a value shown with a point; a
+/// number with both separators is refused and leaves the size as it was.
+#[test]
+fn arithmetic_with_a_decimal_comma_works_in_a_size_field() {
+    let surfaces: [(&str, Draw); 3] =
+        [("Transform panel", transform::show), ("Properties", properties::transform_section), ("Control bar", crate::chrome::control_bar)];
+    for (name, draw) in surfaces {
+        for (text, want) in [("100,5-20,5", 80.0), ("90-0,5*20", 80.0), ("10,5*2", 21.0), ("100.5 pt-20,5", 80.0), ("1.234,5", 100.0)] {
+            let mut app = rect_app();
+            set_field(&mut app, draw, "100 pt", text, End::Enter(Modifiers::NONE));
+            assert_eq!(size(&app), (want, 50.0), "{name}, {text}");
+        }
+    }
+}
+
 /// A length field of the New Document dialog keeps the focus on Ctrl/Cmd+Enter, and the dialog
 /// creates no document.
 #[test]

crates/ui-egui/src/widgets.rs

@@ -441,9 +441,9 @@ mod step_to_multiple_tests {
 mod decimal_point_tests {
     use super::*;
 
-    /// A decimal comma reads as a point, in a length, with arithmetic and in a percentage; text
-    /// with a point keeps its commas and is refused as before, and so does a thousands comma
-    /// (#3837).
+    /// A decimal comma reads as a point, in a length, with arithmetic and in a percentage, next to
+    /// numbers written with a point too (#5684); a number with both separators is refused, and so
+    /// is a thousands comma (#3837).
     #[test]
     fn a_decimal_comma_reads_as_a_point() {
         let mm = |s: &str| Unit::Millimeters.parse(&decimal_point(s)).map(|pt| Unit::Millimeters.from_pt(pt));
@@ -460,6 +460,15 @@ mod decimal_point_tests {
             let got = mm(text).unwrap_or(f64::NAN);
             assert!((got - want).abs() < 1e-9, "{text} is a decimal: {got}");
         }
+        // Each number reads its own separator: a comma typed after a value shown with a point
+        // (#5684). A number with both separators is refused.
+        for (text, want) in [("100,5-20", 80.5), ("100-0,5", 99.5), ("10,5*2", 21.0), ("100.5 mm-0,5", 100.0), ("0,5+100.25", 100.75)] {
+            let got = mm(text).unwrap_or(f64::NAN);
+            assert!((got - want).abs() < 1e-9, "{text}: {got}");
+        }
+        for both in ["1.234,5", "1,234.5", "1.5,5-2"] {
+            assert_eq!(mm(both), None, "{both}: a point and a comma in one number");
+        }
         assert_eq!(share_of("12,5%", 200.0), Some(25.0));
         assert_eq!(share_of("1,000%", 200.0), None, "1,000% reads as thousands: refused, not 1%");
     }

crates/ui-egui/src/widgets/numeric.rs

@@ -20,10 +20,12 @@ pub(crate) fn typed_unit(ctx: &egui::Context, unit: Unit) -> Unit {
 }
 
 /// `text` typed in a numeric field, with a decimal comma read as a point: `0,1 mm` is `0.1 mm`
-/// (#3837). Text with a point keeps its commas, so `1,000.5` is still refused rather than read
-/// with two decimal separators, and so does a number that reads as thousands ([`thousands`]).
+/// (#3837), and each number of a sum reads its own separator, so `100.5 mm-0,5` (a comma typed
+/// after the value the field shows) is 100 mm (#5684). A number written with both separators has
+/// two points once read, so `1,000.5` and `1.234,5` are refused rather than guessed at; so is a
+/// number that reads as thousands ([`thousands`]).
 pub(super) fn decimal_point(text: &str) -> std::borrow::Cow<'_, str> {
-    if text.contains(',') && !text.contains('.') && !thousands(text) { text.replace(',', ".").into() } else { text.into() }
+    if text.contains(',') && !thousands(text) { text.replace(',', ".").into() } else { text.into() }
 }
 
 /// Is `text` a number written with a thousands comma, as `1,000` or `12,500 mm`: one to three