From ae65660b6b2ed0645f3d9584cbeca856ba8defc6 Mon Sep 17 00:00:00 2001
From: Gerard Porto <gporto@gmail.com>
Date: Mon, 31 Aug 2026 09:27:21 +0200
Subject: [PATCH] Add configurable line number font

---
 .../Controller/TextViewController.swift            |  3 +++
 .../SourceEditorConfiguration+Appearance.swift     |  9 ++++++++-
 .../Controller/TextViewControllerTests.swift       | 14 ++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/Sources/CodeEditSourceEditor/Controller/TextViewController.swift b/Sources/CodeEditSourceEditor/Controller/TextViewController.swift
index fb95c81c1..672708519 100644
--- a/Sources/CodeEditSourceEditor/Controller/TextViewController.swift
+++ b/Sources/CodeEditSourceEditor/Controller/TextViewController.swift
@@ -108,6 +108,9 @@ public class TextViewController: NSViewController {
     /// The font to use in the `textView`
     public var font: NSFont { configuration.appearance.font }
 
+    /// The optional font used for line numbers. When `nil`, the editor derives one from ``font``.
+    public var lineNumberFont: NSFont? { configuration.appearance.lineNumberFont }
+
     /// The  ``EditorTheme`` used for highlighting.
     public var theme: EditorTheme { configuration.appearance.theme }
 
diff --git a/Sources/CodeEditSourceEditor/SourceEditorConfiguration/SourceEditorConfiguration+Appearance.swift b/Sources/CodeEditSourceEditor/SourceEditorConfiguration/SourceEditorConfiguration+Appearance.swift
index 6ca03f2a7..399c2bfeb 100644
--- a/Sources/CodeEditSourceEditor/SourceEditorConfiguration/SourceEditorConfiguration+Appearance.swift
+++ b/Sources/CodeEditSourceEditor/SourceEditorConfiguration/SourceEditorConfiguration+Appearance.swift
@@ -19,6 +19,9 @@ extension SourceEditorConfiguration {
         /// The default font.
         public var font: NSFont
 
+        /// An optional font for line numbers. When `nil`, a font derived from ``font`` is used.
+        public var lineNumberFont: NSFont?
+
         /// The line height multiplier (e.g. `1.2`).
         public var lineHeightMultiple: Double
 
@@ -45,6 +48,7 @@ extension SourceEditorConfiguration {
         ///   - useThemeBackground: Determines whether the editor uses the theme's background color, or a transparent
         ///                         background color.
         ///   - font: The default font.
+        ///   - lineNumberFont: An optional font for line numbers. Defaults to a font derived from `font`.
         ///   - lineHeightMultiple: The line height multiplier (e.g. `1.2`).
         ///   - letterSpacing: The amount of space to use between letters, as a percent. Eg: `1.0` = no space, `1.5`
         ///                    = 1/2 of a character's width between characters, etc. Defaults to `1.0`.
@@ -57,6 +61,7 @@ extension SourceEditorConfiguration {
             theme: EditorTheme,
             useThemeBackground: Bool = true,
             font: NSFont,
+            lineNumberFont: NSFont? = nil,
             lineHeightMultiple: Double = 1.2,
             letterSpacing: Double = 1.0,
             wrapLines: Bool,
@@ -67,6 +72,7 @@ extension SourceEditorConfiguration {
             self.theme = theme
             self.useThemeBackground = useThemeBackground
             self.font = font
+            self.lineNumberFont = lineNumberFont
             self.lineHeightMultiple = lineHeightMultiple
             self.letterSpacing = letterSpacing
             self.wrapLines = wrapLines
@@ -86,10 +92,11 @@ extension SourceEditorConfiguration {
             if oldConfig?.font != font {
                 controller.textView.font = font
                 controller.textView.typingAttributes = controller.attributesFor(nil)
-                controller.gutterView.font = font.rulerFont
                 needsHighlighterInvalidation = true
             }
 
+            controller.gutterView.font = lineNumberFont ?? font.rulerFont
+
             if oldConfig?.theme != theme || oldConfig?.useThemeBackground != useThemeBackground {
                 updateControllerNewTheme(controller: controller)
                 needsHighlighterInvalidation = true
diff --git a/Tests/CodeEditSourceEditorTests/Controller/TextViewControllerTests.swift b/Tests/CodeEditSourceEditorTests/Controller/TextViewControllerTests.swift
index bef6615bd..d0ec0a942 100644
--- a/Tests/CodeEditSourceEditorTests/Controller/TextViewControllerTests.swift
+++ b/Tests/CodeEditSourceEditorTests/Controller/TextViewControllerTests.swift
@@ -235,6 +235,20 @@ final class TextViewControllerTests: XCTestCase {
         controller.configuration.appearance.letterSpacing = 1.0
     }
 
+    func test_lineNumberFont() {
+        let defaultFont = controller.font.rulerFont
+        XCTAssertNil(controller.lineNumberFont)
+        XCTAssertEqual(controller.gutterView.font, defaultFont)
+
+        let customFont = NSFont.monospacedSystemFont(ofSize: 17, weight: .bold)
+        controller.configuration.appearance.lineNumberFont = customFont
+        XCTAssertEqual(controller.lineNumberFont, customFont)
+        XCTAssertEqual(controller.gutterView.font, customFont)
+
+        controller.configuration.appearance.lineNumberFont = nil
+        XCTAssertEqual(controller.gutterView.font, defaultFont)
+    }
+
     // MARK: Bracket Highlights
 
     func test_bracketHighlights() throws {