macos: focus split previous/next

macos/Ghostty.xcodeproj/project.pbxproj

@@ -61,6 +61,7 @@
 		A586167C2B7703CC009BDB1D /* fish in Resources */ = {isa = PBXBuildFile; fileRef = A586167B2B7703CC009BDB1D /* fish */; };
 		A586365F2DEE6C2300E04A10 /* SplitTree.swift in Sources */ = {isa = PBXBuildFile; fileRef = A586365E2DEE6C2100E04A10 /* SplitTree.swift */; };
 		A58636662DEF964100E04A10 /* TerminalSplitTreeView.swift in Sources */ = {isa = PBXBuildFile; fileRef = A58636652DEF963F00E04A10 /* TerminalSplitTreeView.swift */; };
+		A586366B2DF0A98C00E04A10 /* Array+Extension.swift in Sources */ = {isa = PBXBuildFile; fileRef = A586366A2DF0A98900E04A10 /* Array+Extension.swift */; };
 		A5874D992DAD751B00E83852 /* CGS.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5874D982DAD751A00E83852 /* CGS.swift */; };
 		A5874D9D2DAD786100E83852 /* NSWindow+Extension.swift in Sources */ = {isa = PBXBuildFile; fileRef = A5874D9C2DAD785F00E83852 /* NSWindow+Extension.swift */; };
 		A59444F729A2ED5200725BBA /* SettingsView.swift in Sources */ = {isa = PBXBuildFile; fileRef = A59444F629A2ED5200725BBA /* SettingsView.swift */; };
@@ -168,6 +169,7 @@
 		A586167B2B7703CC009BDB1D /* fish */ = {isa = PBXFileReference; lastKnownFileType = folder; name = fish; path = "../zig-out/share/fish"; sourceTree = "<group>"; };
 		A586365E2DEE6C2100E04A10 /* SplitTree.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SplitTree.swift; sourceTree = "<group>"; };
 		A58636652DEF963F00E04A10 /* TerminalSplitTreeView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TerminalSplitTreeView.swift; sourceTree = "<group>"; };
+		A586366A2DF0A98900E04A10 /* Array+Extension.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Array+Extension.swift"; sourceTree = "<group>"; };
 		A5874D982DAD751A00E83852 /* CGS.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CGS.swift; sourceTree = "<group>"; };
 		A5874D9C2DAD785F00E83852 /* NSWindow+Extension.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "NSWindow+Extension.swift"; sourceTree = "<group>"; };
 		A59444F629A2ED5200725BBA /* SettingsView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SettingsView.swift; sourceTree = "<group>"; };
@@ -292,6 +294,7 @@
 		A534263D2A7DCBB000EBB7A2 /* Helpers */ = {
 			isa = PBXGroup;
 			children = (
+				A58636692DF0A98100E04A10 /* Extensions */,
 				A5874D9B2DAD781100E83852 /* Private */,
 				A5AEB1642D5BE7BF00513529 /* LastWindowPosition.swift */,
 				A5A6F7292CC41B8700B232A5 /* Xcode.swift */,
@@ -442,6 +445,14 @@
 			path = Splits;
 			sourceTree = "<group>";
 		};
+		A58636692DF0A98100E04A10 /* Extensions */ = {
+			isa = PBXGroup;
+			children = (
+				A586366A2DF0A98900E04A10 /* Array+Extension.swift */,
+			);
+			path = Extensions;
+			sourceTree = "<group>";
+		};
 		A5874D9B2DAD781100E83852 /* Private */ = {
 			isa = PBXGroup;
 			children = (
@@ -721,6 +732,7 @@
 				A55B7BBC29B6FC330055DE60 /* SurfaceView.swift in Sources */,
 				A5333E1C2B5A1CE3008AEFF7 /* CrossKit.swift in Sources */,
 				A5874D992DAD751B00E83852 /* CGS.swift in Sources */,
+				A586366B2DF0A98C00E04A10 /* Array+Extension.swift in Sources */,
 				A59444F729A2ED5200725BBA /* SettingsView.swift in Sources */,
 				A56D58862ACDDB4100508D2C /* Ghostty.Shell.swift in Sources */,
 				A5985CD72C320C4500C57AD3 /* String+Extension.swift in Sources */,

macos/Sources/Features/Splits/SplitTree.swift

@@ -50,6 +50,20 @@ struct SplitTree<ViewType: NSView & Codable>: Codable {
         case down
         case up
     }
+
+    /// The direction that focus can move from a node.
+    enum FocusDirection {
+        // Follow a consistent tree-like structure.
+        case previous
+        case next
+
+        // Geospatially-aware navigation targets. These take into account the
+        // dimensions of the view to find the correct node to go to.
+        case up
+        case down
+        case left
+        case right
+    }
 }
 
 // MARK: SplitTree
@@ -111,6 +125,44 @@ extension SplitTree {
         
         return .init(root: newRoot, zoomed: newZoomed)
     }
+    
+    /// Find the next view to focus based on the current focused node and direction
+    func focusTarget(for direction: FocusDirection, from currentNode: Node) -> ViewType? {
+        guard let root else { return nil }
+        
+        switch direction {
+        case .previous:
+            // For previous, we traverse in order and find the previous leaf from our leftmost
+            let allLeaves = root.leaves()
+            let currentView = currentNode.leftmostLeaf()
+            guard let currentIndex = allLeaves.firstIndex(where: { $0 === currentView }) else {
+                // Shouldn't be possible leftmostLeaf can't return something that doesn't exist!
+                return nil
+            }
+            let index = allLeaves.indexWrapping(before: currentIndex)
+            return allLeaves[index]
+
+        case .next:
+            // For previous, we traverse in order and find the next leaf from our rightmost
+            let allLeaves = root.leaves()
+            let currentView = currentNode.rightmostLeaf()
+            guard let currentIndex = allLeaves.firstIndex(where: { $0 === currentView }) else {
+                return nil
+            }
+            let index = allLeaves.indexWrapping(after: currentIndex)
+            return allLeaves[index]
+
+        case .up, .down, .left, .right:
+            // For directional movement, we need to traverse the tree structure
+            return directionalTarget(for: direction, from: currentNode)
+        }
+    }
+    
+    /// Find focus target in a specific direction by traversing split boundaries
+    private func directionalTarget(for direction: FocusDirection, from currentNode: Node) -> ViewType? {
+        // TODO
+        return nil
+    }
 }
 
 // MARK: SplitTree.Node
@@ -331,6 +383,26 @@ extension SplitTree.Node {
             ))
         }
     }
+    
+    /// Get the leftmost leaf in this subtree
+    func leftmostLeaf() -> ViewType {
+        switch self {
+        case .leaf(let view):
+            return view
+        case .split(let split):
+            return split.left.leftmostLeaf()
+        }
+    }
+    
+    /// Get the rightmost leaf in this subtree
+    func rightmostLeaf() -> ViewType {
+        switch self {
+        case .leaf(let view):
+            return view
+        case .split(let split):
+            return split.right.rightmostLeaf()
+        }
+    }
 }
 
 // MARK: SplitTree.Node Protocols

macos/Sources/Features/Terminal/BaseTerminalController.swift

@@ -145,6 +145,11 @@ class BaseTerminalController: NSWindowController,
             selector: #selector(ghosttyDidEqualizeSplits(_:)),
             name: Ghostty.Notification.didEqualizeSplits,
             object: nil)
+        center.addObserver(
+            self,
+            selector: #selector(ghosttyDidFocusSplit(_:)),
+            name: Ghostty.Notification.ghosttyFocusSplit,
+            object: nil)
 
         // Listen for local events that we need to know of outside of
         // single surface handlers.
@@ -386,6 +391,38 @@ class BaseTerminalController: NSWindowController,
             _ = container.equalize()
         }
     }
+    
+    @objc private func ghosttyDidFocusSplit(_ notification: Notification) {
+        // The target must be within our tree
+        guard let target = notification.object as? Ghostty.SurfaceView else { return }
+        guard surfaceTree2.root?.node(view: target) != nil else { return }
+
+        // Get the direction from the notification
+        guard let directionAny = notification.userInfo?[Ghostty.Notification.SplitDirectionKey] else { return }
+        guard let direction = directionAny as? Ghostty.SplitFocusDirection else { return }
+        
+        // Convert Ghostty.SplitFocusDirection to our SplitTree.FocusDirection
+        let focusDirection: SplitTree<Ghostty.SurfaceView>.FocusDirection
+        switch direction {
+        case .previous: focusDirection = .previous
+        case .next: focusDirection = .next
+        case .up: focusDirection = .up
+        case .down: focusDirection = .down
+        case .left: focusDirection = .left
+        case .right: focusDirection = .right
+        }
+        
+        // Find the node for the target surface
+        guard let targetNode = surfaceTree2.root?.node(view: target) else { return }
+        
+        // Find the next surface to focus
+        guard let nextSurface = surfaceTree2.focusTarget(for: focusDirection, from: targetNode) else {
+            return
+        }
+
+        // Move focus to the next surface
+        Ghostty.moveFocus(to: nextSurface, from: target)
+    }
 
     // MARK: Local Events
 

macos/Sources/Ghostty/Ghostty.App.swift

@@ -921,7 +921,8 @@ extension Ghostty {
                     // we should only be returning true if we actually performed the action,
                     // but this handles the most common case of caring about goto_split performability
                     // which is the no-split case.
-                    guard controller.surfaceTree?.isSplit ?? false else { return false }
+                    // TODO: fix this
+                    //guard controller.surfaceTree?.isSplit ?? false else { return false }
 
                     NotificationCenter.default.post(
                         name: Notification.ghosttyFocusSplit,

macos/Sources/Helpers/Extensions/Array+Extension.swift

@@ -0,0 +1,19 @@
+extension Array {
+    /// Returns the index before i, with wraparound. Assumes i is a valid index.
+    func indexWrapping(before i: Int) -> Int {
+        if i == 0 {
+            return count - 1
+        }
+
+        return i - 1
+    }
+
+    /// Returns the index after i, with wraparound. Assumes i is a valid index.
+    func indexWrapping(after i: Int) -> Int {
+        if i == count - 1 {
+            return 0
+        }
+
+        return i + 1
+    }
+}