Fix down arrow key not working after font size change

Sources/CodeEditSourceEditor/Controller/TextViewController+Lifecycle.swift

@@ -204,13 +204,25 @@ extension TextViewController {
         }
     }
 
+    // MARK: - Key Codes
+
+    static let tabKeyCode: UInt16 = 0x30
+    static let downArrowKeyCode: UInt16 = 125
+    static let upArrowKeyCode: UInt16 = 126
+
+    /// The set of modifier flags relevant to key binding matching.
+    /// Masks out transient flags like Caps Lock, Fn, and numeric pad that would
+    /// prevent exact-match comparisons from succeeding.
+    private static let relevantModifiers: NSEvent.ModifierFlags = [.shift, .control, .option, .command]
+
     func handleEvent(event: NSEvent) -> NSEvent? {
         let modifierFlags = event.modifierFlags.intersection(.deviceIndependentFlagsMask)
+            .intersection(Self.relevantModifiers)
         switch event.type {
         case .keyDown:
-            let tabKey: UInt16 = 0x30
-
-            if event.keyCode == tabKey {
+            if event.keyCode == Self.downArrowKeyCode || event.keyCode == Self.upArrowKeyCode {
+                return self.handleArrowKey(event: event, modifierFlags: modifierFlags)
+            } else if event.keyCode == Self.tabKeyCode {
                 return self.handleTab(event: event, modifierFlags: modifierFlags.rawValue)
             } else {
                 return self.handleCommand(event: event, modifierFlags: modifierFlags)
@@ -276,11 +288,66 @@ extension TextViewController {
             }
             jumpToDefinitionModel.performJump(at: cursor.range)
             return nil
+        case (controlKey, "n"):
+            self.textView.moveDown(nil)
+            return nil
+        case (controlKey, "p"):
+            self.textView.moveUp(nil)
+            return nil
         case (_, _):
             return event
         }
     }
 
+    /// Handles up/down arrow key events for plain, Shift, Option, Command,
+    /// and their combinations among these modifiers.
+    /// Dispatches the appropriate movement method on the text view and consumes the event.
+    ///
+    /// - Returns: `nil` to consume the event after dispatching the movement action,
+    ///   or the original event for unsupported modifier combinations.
+    private func handleArrowKey(event: NSEvent, modifierFlags: NSEvent.ModifierFlags) -> NSEvent? {
+        let isDown = event.keyCode == Self.downArrowKeyCode
+        let shift = modifierFlags.contains(.shift)
+        let option = modifierFlags.contains(.option)
+        let command = modifierFlags.contains(.command)
+
+        switch (isDown, shift, option, command) {
+        // Plain arrow
+        case (true, false, false, false):
+            self.textView.moveDown(nil)
+        case (false, false, false, false):
+            self.textView.moveUp(nil)
+        // Shift+Arrow (extend selection)
+        case (true, true, false, false):
+            self.textView.moveDownAndModifySelection(nil)
+        case (false, true, false, false):
+            self.textView.moveUpAndModifySelection(nil)
+        // Option+Arrow (paragraph)
+        case (true, false, true, false):
+            self.textView.moveToEndOfParagraph(nil)
+        case (false, false, true, false):
+            self.textView.moveToBeginningOfParagraph(nil)
+        // Cmd+Arrow (document)
+        case (true, false, false, true):
+            self.textView.moveToEndOfDocument(nil)
+        case (false, false, false, true):
+            self.textView.moveToBeginningOfDocument(nil)
+        // Shift+Option+Arrow (extend selection to paragraph)
+        case (true, true, true, false):
+            self.textView.moveToEndOfParagraphAndModifySelection(nil)
+        case (false, true, true, false):
+            self.textView.moveToBeginningOfParagraphAndModifySelection(nil)
+        // Shift+Cmd+Arrow (extend selection to document)
+        case (true, true, false, true):
+            self.textView.moveToEndOfDocumentAndModifySelection(nil)
+        case (false, true, false, true):
+            self.textView.moveToBeginningOfDocumentAndModifySelection(nil)
+        default:
+            return event
+        }
+        return nil
+    }
+
     /// Handles the tab key event.
     /// If the Shift key is pressed, it handles unindenting. If no modifier key is pressed, it checks if multiple lines
     /// are highlighted and handles indenting accordingly.

Sources/CodeEditSourceEditor/Controller/TextViewController.swift

@@ -163,6 +163,21 @@ public class TextViewController: NSViewController {
     /// Toggle the visibility of the gutter view in the editor.
     public var showGutter: Bool { configuration.peripherals.showGutter }
 
+    /// Optional provider for custom gutter decorations.
+    public var gutterDecorationProvider: (any GutterDecorationProviding)? {
+        didSet {
+            gutterView.decorationProvider = gutterDecorationProvider
+            gutterView.needsDisplay = true
+        }
+    }
+
+    /// Optional interaction delegate for gutter decorations.
+    public var gutterDecorationInteractionDelegate: (any GutterDecorationInteractionDelegate)? {
+        didSet {
+            gutterView.decorationInteractionDelegate = gutterDecorationInteractionDelegate
+        }
+    }
+
     /// Toggle the visibility of the minimap view in the editor.
     public var showMinimap: Bool { configuration.peripherals.showMinimap }
 
@@ -290,6 +305,16 @@ public class TextViewController: NSViewController {
         self.gutterView.setNeedsDisplay(self.gutterView.frame)
     }
 
+    /// Force the layout manager to recalculate its cached estimated line height.
+    ///
+    /// The estimated line height is cached and not invalidated when the font or line height multiplier changes,
+    /// causing vertical cursor movement (`moveDown:`/`moveUp:`) to use stale values and fail to cross line
+    /// boundaries. Re-assigning `renderDelegate` triggers the cache to refresh.
+    func refreshEstimatedLineHeightCache() {
+        let renderDelegate = textView.layoutManager.renderDelegate
+        textView.layoutManager.renderDelegate = renderDelegate
+    }
+
     deinit {
         if let highlighter {
             textView.removeStorageDelegate(highlighter)

Sources/CodeEditSourceEditor/SourceEditorConfiguration/SourceEditorConfiguration+Appearance.swift

@@ -87,6 +87,7 @@ extension SourceEditorConfiguration {
                 controller.textView.font = font
                 controller.textView.typingAttributes = controller.attributesFor(nil)
                 controller.gutterView.font = font.rulerFont
+                controller.refreshEstimatedLineHeightCache()
                 needsHighlighterInvalidation = true
             }
 
@@ -103,6 +104,7 @@ extension SourceEditorConfiguration {
 
             if oldConfig?.lineHeightMultiple != lineHeightMultiple {
                 controller.textView.layoutManager.lineHeightMultiplier = lineHeightMultiple
+                controller.refreshEstimatedLineHeightCache()
             }
 
             if oldConfig?.wrapLines != wrapLines {