From 22819f8a296e799b75904f03ddf1d4204fd9c6be Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <m@mitchellh.com>
Date: Wed, 4 Jun 2025 11:40:54 -0700
Subject: [PATCH] macos: transfer doesBorderTop

---
 macos/Sources/Features/Splits/SplitTree.swift | 33 +++++++++++++++++++
 .../Terminal/TerminalController.swift         | 10 ++++--
 2 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/macos/Sources/Features/Splits/SplitTree.swift b/macos/Sources/Features/Splits/SplitTree.swift
index f458b5dee..78bed7120 100644
--- a/macos/Sources/Features/Splits/SplitTree.swift
+++ b/macos/Sources/Features/Splits/SplitTree.swift
@@ -774,6 +774,39 @@ extension SplitTree.Spatial {
             }
         }
     }
+
+    /// Returns whether the given node borders the specified side of the spatial bounds.
+    ///
+    /// This method checks if a node's bounds touch the edge of the overall spatial area:
+    /// - **Up**: Node's top edge touches the top of the spatial area (Y=0)
+    /// - **Down**: Node's bottom edge touches the bottom of the spatial area (Y=maxY)
+    /// - **Left**: Node's left edge touches the left of the spatial area (X=0)
+    /// - **Right**: Node's right edge touches the right of the spatial area (X=maxX)
+    ///
+    /// - Parameters:
+    ///   - side: The side of the spatial bounds to check
+    ///   - node: The node to check if it borders the specified side
+    /// - Returns: True if the node borders the specified side, false otherwise
+    func doesBorder(side: Direction, from node: SplitTree.Node) -> Bool {
+        // Find the slot for this node
+        guard let slot = slots.first(where: { $0.node == node }) else { return false }
+        
+        // Calculate the overall bounds of all slots
+        let overallBounds = slots.reduce(CGRect.null) { result, slot in
+            result.union(slot.bounds)
+        }
+        
+        return switch side {
+        case .up: 
+            slot.bounds.minY == overallBounds.minY
+        case .down:
+            slot.bounds.maxY == overallBounds.maxY
+        case .left:
+            slot.bounds.minX == overallBounds.minX
+        case .right:
+            slot.bounds.maxX == overallBounds.maxX
+        }
+    }
 }
 
 // MARK: SplitTree.Node Protocols
diff --git a/macos/Sources/Features/Terminal/TerminalController.swift b/macos/Sources/Features/Terminal/TerminalController.swift
index 120ac6377..eb140b2a3 100644
--- a/macos/Sources/Features/Terminal/TerminalController.swift
+++ b/macos/Sources/Features/Terminal/TerminalController.swift
@@ -282,15 +282,19 @@ class TerminalController: BaseTerminalController {
         // If it does, we match the focused surface. If it doesn't, we use the app
         // configuration.
         let backgroundColor: OSColor
-        if let surfaceTree {
-            if let focusedSurface, surfaceTree.doesBorderTop(view: focusedSurface) {
+        if !surfaceTree2.isEmpty {
+            if let focusedSurface = focusedSurface,
+               let treeRoot = surfaceTree2.root,
+               let focusedNode = treeRoot.node(view: focusedSurface),
+               treeRoot.spatial().doesBorder(side: .up, from: focusedNode) {
                 // Similar to above, an alpha component of "0" causes compositor issues, so
                 // we use 0.001. See: https://github.com/ghostty-org/ghostty/pull/4308
                 backgroundColor = OSColor(focusedSurface.backgroundColor ?? surfaceConfig.backgroundColor).withAlphaComponent(0.001)
             } else {
                 // We don't have a focused surface or our surface doesn't border the
                 // top. We choose to match the color of the top-left most surface.
-                backgroundColor = OSColor(surfaceTree.topLeft().backgroundColor ?? derivedConfig.backgroundColor)
+                let topLeftSurface = surfaceTree2.root?.leftmostLeaf()
+                backgroundColor = OSColor(topLeftSurface?.backgroundColor ?? derivedConfig.backgroundColor)
             }
         } else {
             backgroundColor = OSColor(self.derivedConfig.backgroundColor)