macOS: add bottom bar when child exits

macos/Sources/Ghostty/Ghostty.App.swift

@@ -662,8 +662,7 @@ extension Ghostty {
             case GHOSTTY_ACTION_QUIT_TIMER:
                 fallthrough
             case GHOSTTY_ACTION_SHOW_CHILD_EXITED:
-                Ghostty.logger.info("known but unimplemented action action=\(action.tag.rawValue)")
-                return false
+                return showChildExited(app, target: target, v: action.action.child_exited)
             case GHOSTTY_ACTION_COPY_TITLE_TO_CLIPBOARD:
                 return copyTitleToClipboard(app, target: target)
             default:
@@ -1632,6 +1631,25 @@ extension Ghostty {
             }
         }
 
+        private static func showChildExited(
+            _ app: ghostty_app_t,
+            target: ghostty_target_s,
+            v: ghostty_surface_message_childexited_s,
+        ) -> Bool {
+            switch target.tag {
+            case GHOSTTY_TARGET_SURFACE:
+                guard let surface = target.target.surface else { return false }
+                guard let surfaceView = self.surfaceView(from: surface) else { return false }
+                // We handle this when the window is visible and timetime_ms is greater than 0,
+                // which will rule out exit codes on launch
+                guard surfaceView.window != nil, v.timetime_ms > 0 else { return false }
+                surfaceView.setChildExitedMessage(.init(v))
+                return true
+            default:
+                return false
+            }
+        }
+
         private static func copyTitleToClipboard(
             _ app: ghostty_app_t,
             target: ghostty_target_s) -> Bool {

macos/Sources/Ghostty/Ghostty.ChildExitedMessage.swift

@@ -0,0 +1,23 @@
+import Foundation
+import GhosttyKit
+import SwiftUI
+
+extension Ghostty {
+    struct ChildExitedMessage {
+        enum Level {
+            case success, error
+        }
+        let text: String
+        let level: Level
+
+        init(_ message: ghostty_surface_message_childexited_s) {
+            switch Int(message.exit_code) {
+            case Int(EXIT_SUCCESS):
+                level = .success
+            default:
+                level = .error
+            }
+            text = "Process exited. Press any key to close the terminal."
+        }
+    }
+}

macos/Sources/Ghostty/Surface View/ChildExitedMessageBar.swift

@@ -0,0 +1,46 @@
+import SwiftUI
+
+struct ChildExitedMessageBar: View {
+    let msg: Ghostty.ChildExitedMessage
+    @State private var isHovered: Bool = false
+
+    var body: some View {
+        HStack(spacing: 6) {
+            Text(msg.text)
+                .fontWeight(.medium)
+                .lineLimit(1)
+                .truncationMode(.tail)
+        }
+        .padding(.horizontal, 8)
+        .padding(.vertical, 4)
+        .frame(maxWidth: .infinity, alignment: .center)
+        .background(msg.level.backgroundStyle)
+        .foregroundColor(msg.level.foregroundColor)
+        .contentShape(.rect)
+        .accessibilityLabel(msg.text)
+        .transition(.move(edge: .bottom))
+        .opacity(isHovered ? 0 : 1)
+        .allowsHitTesting(false)
+        .overlay {
+            Color.clear
+                .onHover {
+                    isHovered = $0
+                }
+        }
+    }
+}
+
+private extension Ghostty.ChildExitedMessage.Level {
+    var foregroundColor: Color {
+        .primary
+    }
+
+    var backgroundStyle: AnyShapeStyle {
+        switch self {
+        case .success:
+            AnyShapeStyle(.background)
+        case .error:
+            AnyShapeStyle(.red.opacity(0.5))
+        }
+    }
+}

macos/Sources/Ghostty/Surface View/OSSurfaceView.swift

@@ -51,6 +51,9 @@ extension Ghostty {
         /// True when the surface should show a highlight effect (e.g., when presented via goto_split).
         @Published private(set) var highlighted: Bool = false
 
+        /// A message sent from `ghostty_surface_t` when a child process exited
+        @Published private(set) var childExitedMessage: ChildExitedMessage?
+
         var surface: ghostty_surface_t? {
             nil
         }
@@ -92,6 +95,10 @@ extension Ghostty {
             }
         }
 
+        func setChildExitedMessage(_ message: ChildExitedMessage) {
+            self.childExitedMessage = message
+        }
+
         // MARK: - Placeholders
 
         func focusDidChange(_ focused: Bool) {}

macos/Sources/Ghostty/Surface View/SurfaceView.swift

@@ -137,6 +137,12 @@ extension Ghostty {
                     if let url = surfaceView.hoverUrl {
                         URLHoverBanner(url: url)
                     }
+
+                    // Show a bar to indicate a child process has exited.
+                    if let msg = surfaceView.childExitedMessage {
+                        ChildExitedMessageBar(msg: msg)
+                            .font(.system(size: min(surfaceView.cellSize.height * 0.8, 30)))
+                    }
                 }
                 .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .bottom)