Follow up PR 242: refresh browser under-page background on theme updates (#272)

* Address PR 242 follow-ups for titlebar and browser background

* Restore titlebar border per follow-up scope

* Refresh browser under-page color with Ghostty opacity

* Browser: theme blank page fallback for about:blank

* Browser: keep new tabs webview-less until first nav

Sources/Panels/BrowserPanel.swift

@@ -1005,6 +1005,27 @@ final class BrowserPanel: Panel, ObservableObject {
     /// Shared process pool for cookie sharing across all browser panels
     private static let sharedProcessPool = WKProcessPool()
 
+    private static func clampedGhosttyBackgroundOpacity(_ opacity: Double) -> CGFloat {
+        CGFloat(max(0.0, min(1.0, opacity)))
+    }
+
+    private static func resolvedGhosttyBackgroundColor(from notification: Notification? = nil) -> NSColor {
+        let userInfo = notification?.userInfo
+        let baseColor = (userInfo?[GhosttyNotificationKey.backgroundColor] as? NSColor)
+            ?? GhosttyApp.shared.defaultBackgroundColor
+
+        let opacity: Double
+        if let value = userInfo?[GhosttyNotificationKey.backgroundOpacity] as? Double {
+            opacity = value
+        } else if let value = userInfo?[GhosttyNotificationKey.backgroundOpacity] as? NSNumber {
+            opacity = value.doubleValue
+        } else {
+            opacity = GhosttyApp.shared.defaultBackgroundOpacity
+        }
+
+        return baseColor.withAlphaComponent(clampedGhosttyBackgroundOpacity(opacity))
+    }
+
     let id: UUID
     let panelType: PanelType = .browser
 
@@ -1027,6 +1048,10 @@ final class BrowserPanel: Panel, ObservableObject {
     /// Published URL being displayed
     @Published private(set) var currentURL: URL?
 
+    /// Whether the browser panel should render its WKWebView in the content area.
+    /// New browser tabs stay in an empty "new tab" state until first navigation.
+    @Published private(set) var shouldRenderWebView: Bool = false
+
     /// Published page title
     @Published private(set) var pageTitle: String = ""
 
@@ -1090,7 +1115,7 @@ final class BrowserPanel: Panel, ObservableObject {
         if let url = currentURL {
             return url.host ?? url.absoluteString
         }
-        return "Browser"
+        return "New tab"
     }
 
     var displayIcon: String? {
@@ -1130,7 +1155,7 @@ final class BrowserPanel: Panel, ObservableObject {
 
         // Match the empty-page background to the terminal theme so newly-created browsers
         // don't flash white before content loads.
-        webView.underPageBackgroundColor = GhosttyApp.shared.defaultBackgroundColor
+        webView.underPageBackgroundColor = Self.resolvedGhosttyBackgroundColor()
 
         // Always present as Safari.
         webView.customUserAgent = BrowserUserAgentSettings.safariUserAgent
@@ -1206,6 +1231,7 @@ final class BrowserPanel: Panel, ObservableObject {
 
         // Navigate to initial URL if provided
         if let url = initialURL {
+            shouldRenderWebView = true
             navigate(to: url)
         }
     }
@@ -1295,6 +1321,13 @@ final class BrowserPanel: Panel, ObservableObject {
             }
         }
         webViewObservers.append(progressObserver)
+
+        NotificationCenter.default.publisher(for: .ghosttyDefaultBackgroundDidChange)
+            .sink { [weak self] notification in
+                guard let self else { return }
+                self.webView.underPageBackgroundColor = Self.resolvedGhosttyBackgroundColor(from: notification)
+            }
+            .store(in: &cancellables)
     }
 
     // MARK: - Panel Protocol
@@ -1337,6 +1370,7 @@ final class BrowserPanel: Panel, ObservableObject {
         navigationDelegate = nil
         uiDelegate = nil
         webViewObservers.removeAll()
+        cancellables.removeAll()
         faviconTask?.cancel()
         faviconTask = nil
     }
@@ -1547,6 +1581,7 @@ final class BrowserPanel: Panel, ObservableObject {
         guard let url = request.url else { return }
         // Some installs can end up with a legacy Chrome UA override; keep this pinned.
         webView.customUserAgent = BrowserUserAgentSettings.safariUserAgent
+        shouldRenderWebView = true
         if recordTypedNavigation {
             BrowserHistoryStore.shared.recordTypedNavigation(url: url)
         }
@@ -1649,6 +1684,7 @@ final class BrowserPanel: Panel, ObservableObject {
             BrowserWindowPortalRegistry.detach(webView: webView)
         }
         webViewObservers.removeAll()
+        cancellables.removeAll()
     }
 }
 

Sources/Panels/BrowserPanelView.swift

@@ -548,25 +548,38 @@ struct BrowserPanelView: View {
     }
 
     private var webView: some View {
-        WebViewRepresentable(
-            panel: panel,
-            shouldAttachWebView: isVisibleInUI,
-            shouldFocusWebView: isFocused && !addressBarFocused,
-            isPanelFocused: isFocused,
-            portalZPriority: portalPriority
-        )
-            // Keep the representable identity stable across bonsplit structural updates.
-            // This reduces WKWebView reparenting churn (and the associated WebKit crashes).
-            .id(panel.id)
-            .contentShape(Rectangle())
-            .simultaneousGesture(TapGesture().onEnded {
-                // Chrome-like behavior: clicking web content while editing the
-                // omnibar should commit blur and revert transient edits.
-                if addressBarFocused {
-                    addressBarFocused = false
-                }
-            })
-            .zIndex(0)
+        Group {
+            if panel.shouldRenderWebView {
+                WebViewRepresentable(
+                    panel: panel,
+                    shouldAttachWebView: isVisibleInUI,
+                    shouldFocusWebView: isFocused && !addressBarFocused,
+                    isPanelFocused: isFocused,
+                    portalZPriority: portalPriority
+                )
+                // Keep the representable identity stable across bonsplit structural updates.
+                // This reduces WKWebView reparenting churn (and the associated WebKit crashes).
+                .id(panel.id)
+                .contentShape(Rectangle())
+                .simultaneousGesture(TapGesture().onEnded {
+                    // Chrome-like behavior: clicking web content while editing the
+                    // omnibar should commit blur and revert transient edits.
+                    if addressBarFocused {
+                        addressBarFocused = false
+                    }
+                })
+            } else {
+                Color(nsColor: GhosttyApp.shared.defaultBackgroundColor)
+                    .contentShape(Rectangle())
+                    .onTapGesture {
+                        onRequestPanelFocus()
+                        if addressBarFocused {
+                            addressBarFocused = false
+                        }
+                    }
+            }
+        }
+        .zIndex(0)
     }
 
     private func triggerFocusFlashAnimation() {

cmuxTests/CmuxWebViewKeyEquivalentTests.swift

@@ -214,6 +214,41 @@ final class BrowserDeveloperToolsConfigurationTests: XCTestCase {
             XCTAssertTrue(panel.webView.isInspectable)
         }
     }
+
+    func testBrowserPanelRefreshesUnderPageBackgroundColorWhenGhosttyBackgroundChanges() {
+        let panel = BrowserPanel(workspaceId: UUID())
+        let updatedColor = NSColor(srgbRed: 0.18, green: 0.29, blue: 0.44, alpha: 1.0)
+        let updatedOpacity = 0.57
+
+        NotificationCenter.default.post(
+            name: .ghosttyDefaultBackgroundDidChange,
+            object: nil,
+            userInfo: [
+                GhosttyNotificationKey.backgroundColor: updatedColor,
+                GhosttyNotificationKey.backgroundOpacity: updatedOpacity
+            ]
+        )
+
+        guard let actual = panel.webView.underPageBackgroundColor?.usingColorSpace(.sRGB),
+              let expected = updatedColor.withAlphaComponent(updatedOpacity).usingColorSpace(.sRGB) else {
+            XCTFail("Expected sRGB-convertible under-page background colors")
+            return
+        }
+
+        XCTAssertEqual(actual.redComponent, expected.redComponent, accuracy: 0.005)
+        XCTAssertEqual(actual.greenComponent, expected.greenComponent, accuracy: 0.005)
+        XCTAssertEqual(actual.blueComponent, expected.blueComponent, accuracy: 0.005)
+        XCTAssertEqual(actual.alphaComponent, expected.alphaComponent, accuracy: 0.005)
+    }
+
+    func testBrowserPanelStartsAsNewTabWithoutLoadingAboutBlank() {
+        let panel = BrowserPanel(workspaceId: UUID())
+
+        XCTAssertEqual(panel.displayTitle, "New tab")
+        XCTAssertFalse(panel.shouldRenderWebView)
+        XCTAssertNil(panel.webView.url)
+        XCTAssertNil(panel.currentURL)
+    }
 }
 
 @MainActor