macos: setup sequence for SplitTree

macos/Sources/Features/Splits/SplitTree.swift

@@ -350,3 +350,30 @@ extension SplitTree.Node: Equatable {
         }
     }
 }
+
+// MARK: SplitTree Sequences
+
+extension SplitTree.Node {
+    /// Returns all leaf views in this subtree
+    func leaves() -> [NSView] {
+        switch self {
+        case .leaf(let view):
+            return [view]
+            
+        case .split(let split):
+            return split.left.leaves() + split.right.leaves()
+        }
+    }
+}
+
+extension SplitTree: Sequence {
+    func makeIterator() -> [NSView].Iterator {
+        return root?.leaves().makeIterator() ?? [].makeIterator()
+    }
+}
+
+extension SplitTree.Node: Sequence {
+    func makeIterator() -> [NSView].Iterator {
+        return leaves().makeIterator()
+    }
+}

macos/Sources/Features/Terminal/BaseTerminalController.swift

@@ -175,16 +175,16 @@ class BaseTerminalController: NSWindowController,
     /// Update all surfaces with the focus state. This ensures that libghostty has an accurate view about
     /// what surface is focused. This must be called whenever a surface OR window changes focus.
     func syncFocusToSurfaceTree() {
-        guard let tree = self.surfaceTree else { return }
-
-        for leaf in tree {
+        for view in surfaceTree2 {
+            if let surfaceView = view as? Ghostty.SurfaceView {
                 // Our focus state requires that this window is key and our currently
-            // focused surface is the surface in this leaf.
+                // focused surface is the surface in this view.
                 let focused: Bool = (window?.isKeyWindow ?? false) &&
                     !commandPaletteIsShowing &&
                     focusedSurface != nil &&
-                leaf.surface == focusedSurface!
-            leaf.surface.focusDidChange(focused)
+                    surfaceView == focusedSurface!
+                surfaceView.focusDidChange(focused)
+            }
         }
     }
 
@@ -387,21 +387,19 @@ class BaseTerminalController: NSWindowController,
     }
 
     private func localEventFlagsChanged(_ event: NSEvent) -> NSEvent? {
-        // Go through all our surfaces and notify it that the flags changed.
-        if let surfaceTree {
-            var surfaces: [Ghostty.SurfaceView] = surfaceTree.map { $0.surface }
+        // Also update surfaceTree2
+        var surfaces2: [Ghostty.SurfaceView] = surfaceTree2.compactMap { $0 as? Ghostty.SurfaceView }
         
         // If we're the main window receiving key input, then we want to avoid
         // calling this on our focused surface because that'll trigger a double
         // flagsChanged call.
         if NSApp.mainWindow == window {
-                surfaces = surfaces.filter { $0 != focusedSurface }
+            surfaces2 = surfaces2.filter { $0 != focusedSurface }
         }
         
-            for surface in surfaces {
+        for surface in surfaces2 {
             surface.flagsChanged(with: event)
         }
-        }
 
         return event
     }
@@ -675,10 +673,10 @@ class BaseTerminalController: NSWindowController,
     }
 
     func windowDidChangeOcclusionState(_ notification: Notification) {
-        guard let surfaceTree = self.surfaceTree else { return }
         let visible = self.window?.occlusionState.contains(.visible) ?? false
-        for leaf in surfaceTree {
-            if let surface = leaf.surface.surface {
+        for view in surfaceTree2 {
+            if let surfaceView = view as? Ghostty.SurfaceView,
+               let surface = surfaceView.surface {
                 ghostty_surface_set_occlusion(surface, visible)
             }
         }

macos/Sources/Ghostty/Ghostty.SplitNode.swift

@@ -11,7 +11,7 @@ extension Ghostty {
     ///   "container" which has a recursive top/left SplitNode and bottom/right SplitNode. These
     ///   values can further be split infinitely.
     ///
-    enum SplitNode: Equatable, Hashable, Codable, Sequence {
+    enum SplitNode: Equatable, Hashable, Codable {
         case leaf(Leaf)
         case split(Container)