macos: plumb through the split divider color

macos/Sources/Ghostty/Ghostty.Config.swift

@@ -258,5 +258,14 @@ extension Ghostty {
                 blue: blue / 255
             )
         }
+        
+        // This isn't actually a configurable value currently but it could be done day.
+        // We put it here because it is a color that changes depending on the configuration.
+        var splitDividerColor: Color {
+            let backgroundColor = NSColor(backgroundColor)
+            let isLightBackground = backgroundColor.isLightColor
+            let newColor = isLightBackground ? backgroundColor.shadow(withLevel: 0.1) : backgroundColor.shadow(withLevel: 0.4)
+            return Color(nsColor: newColor ?? .gray.withAlphaComponent(0.5))
+        }
     }
 }

macos/Sources/Ghostty/Ghostty.TerminalSplit.swift

@@ -280,6 +280,8 @@ extension Ghostty {
     
     /// This represents a split view that is in the horizontal or vertical split state.
     private struct TerminalSplitContainer: View {
+        @EnvironmentObject var ghostty: Ghostty.App
+
         let neighbors: SplitNode.Neighbors
         @Binding var node: SplitNode?
         @StateObject var container: SplitNode.Container
@@ -288,6 +290,7 @@ extension Ghostty {
             SplitView(
                 container.direction,
                 $container.split,
+                dividerColor: ghostty.config.splitDividerColor,
                 resizeIncrements: .init(width: 1, height: 1),
                 resizePublisher: container.resizeEvent,
                 left: {

macos/Sources/Ghostty/InspectorView.swift

@@ -6,6 +6,8 @@ import GhosttyKit
 extension Ghostty {
     /// InspectableSurface is a type of Surface view that allows an inspector to be attached.
     struct InspectableSurface: View {
+        @EnvironmentObject var ghostty: Ghostty.App
+
         /// Same as SurfaceWrapper, see the doc comments there.
         @ObservedObject var surfaceView: SurfaceView
         var isSplit: Bool = false
@@ -24,7 +26,7 @@ extension Ghostty {
                 if (!surfaceView.inspectorVisible) {
                     SurfaceWrapper(surfaceView: surfaceView, isSplit: isSplit)
                 } else {
-                    SplitView(.vertical, $split, left: {
+                    SplitView(.vertical, $split, dividerColor: ghostty.config.splitDividerColor, left: {
                         SurfaceWrapper(surfaceView: surfaceView, isSplit: isSplit)
                     }, right: {
                         InspectorViewRepresentable(surfaceView: surfaceView)

macos/Sources/Helpers/SplitView/SplitView.Divider.swift

@@ -3,11 +3,10 @@ import SwiftUI
 extension SplitView {
     /// The split divider that is rendered and can be used to resize a split view.
     struct Divider: View {
-        @EnvironmentObject var ghostty: Ghostty.App
-
         let direction: SplitViewDirection
         let visibleSize: CGFloat
         let invisibleSize: CGFloat
+        let color: Color
         
         private var visibleWidth: CGFloat? {
             switch (direction) {
@@ -45,14 +44,6 @@ extension SplitView {
             }
         }
 
-        private var color: Color {
-            let backgroundColor = NSColor(ghostty.config.backgroundColor)
-            let isLightBackground = backgroundColor.isLightColor
-            let newColor = isLightBackground ? backgroundColor.shadow(withLevel: 0.1) : backgroundColor.shadow(withLevel: 0.4)
-
-            return Color(nsColor: newColor ?? .gray.withAlphaComponent(0.5))
-        }
-
         var body: some View {
             ZStack {
                 Color.clear

macos/Sources/Helpers/SplitView/SplitView.swift

@@ -10,6 +10,9 @@ struct SplitView<L: View, R: View>: View {
     /// Direction of the split
     let direction: SplitViewDirection
     
+    /// Divider color
+    let dividerColor: Color
+    
     /// If set, the split view supports programmatic resizing via events sent via the publisher.
     /// Minimum increment (in points) that this split can be resized by, in
     /// each direction. Both `height` and `width` should be whole numbers
@@ -45,7 +48,10 @@ struct SplitView<L: View, R: View>: View {
                 right
                     .frame(width: rightRect.size.width, height: rightRect.size.height)
                     .offset(x: rightRect.origin.x, y: rightRect.origin.y)
-                Divider(direction: direction, visibleSize: splitterVisibleSize, invisibleSize: splitterInvisibleSize)
+                Divider(direction: direction, 
+                        visibleSize: splitterVisibleSize,
+                        invisibleSize: splitterInvisibleSize,
+                        color: dividerColor)
                     .position(splitterPoint)
                     .gesture(dragGesture(geo.size, splitterPoint: splitterPoint))
             }
@@ -57,10 +63,15 @@ struct SplitView<L: View, R: View>: View {
     
     /// Initialize a split view. This view isn't programmatically resizable; it can only be resized
     /// by manually dragging the divider.
-    init(_ direction: SplitViewDirection, _ split: Binding<CGFloat>, @ViewBuilder left: (() -> L), @ViewBuilder right: (() -> R)) {
+    init(_ direction: SplitViewDirection, 
+         _ split: Binding<CGFloat>, 
+         dividerColor: Color,
+         @ViewBuilder left: (() -> L),
+         @ViewBuilder right: (() -> R)) {
         self.init(
             direction,
             split,
+            dividerColor: dividerColor,
             resizeIncrements: .init(width: 1, height: 1),
             resizePublisher: .init(),
             left: left,
@@ -72,6 +83,7 @@ struct SplitView<L: View, R: View>: View {
     init(
         _ direction: SplitViewDirection,
         _ split: Binding<CGFloat>,
+        dividerColor: Color,
         resizeIncrements: NSSize,
         resizePublisher: PassthroughSubject<Double, Never>,
         @ViewBuilder left: (() -> L),
@@ -79,6 +91,7 @@ struct SplitView<L: View, R: View>: View {
     ) {
         self.direction = direction
         self._split = split
+        self.dividerColor = dividerColor
         self.resizeIncrements = resizeIncrements
         self.resizePublisher = resizePublisher
         self.left = left()