Fix browser pane flicker during multi-split resize

Sources/BrowserWindowPortal.swift

@@ -8,6 +8,7 @@ private var cmuxWindowBrowserPortalKey: UInt8 = 0
 private var cmuxWindowBrowserPortalCloseObserverKey: UInt8 = 0
 private var cmuxBrowserSearchOverlayPanelIdAssociationKey: UInt8 = 0
 private var cmuxBrowserPortalNeedsRenderingStateReattachKey: UInt8 = 0
+private var cmuxWindowInteractiveSplitDividerDragKey: UInt8 = 0
 
 #if DEBUG
 private func browserPortalDebugToken(_ view: NSView?) -> String {
@@ -44,6 +45,35 @@ private extension NSResponder {
     }
 }
 
+private extension NSWindow {
+    var browserPortalHasInteractiveSplitDividerDrag: Bool {
+        get {
+            let isActive =
+                (objc_getAssociatedObject(self, &cmuxWindowInteractiveSplitDividerDragKey) as? NSNumber)?
+                    .boolValue ?? false
+            guard isActive else { return false }
+            guard (NSEvent.pressedMouseButtons & 1) != 0 else {
+                objc_setAssociatedObject(
+                    self,
+                    &cmuxWindowInteractiveSplitDividerDragKey,
+                    NSNumber(value: false),
+                    .OBJC_ASSOCIATION_RETAIN_NONATOMIC
+                )
+                return false
+            }
+            return true
+        }
+        set {
+            objc_setAssociatedObject(
+                self,
+                &cmuxWindowInteractiveSplitDividerDragKey,
+                NSNumber(value: newValue),
+                .OBJC_ASSOCIATION_RETAIN_NONATOMIC
+            )
+        }
+    }
+}
+
 private extension WKWebView {
     private var browserPortalNeedsRenderingStateReattach: Bool {
         get {
@@ -2057,6 +2087,13 @@ final class WindowBrowserSlotView: NSView {
 final class WindowBrowserPortal: NSObject {
     private static let transientRecoveryRetryBudget: Int = 12
 
+    private static func dividerHitRectContains(_ point: NSPoint, rect: NSRect) -> Bool {
+        point.x >= rect.minX &&
+            point.x <= rect.maxX &&
+            point.y >= rect.minY &&
+            point.y <= rect.maxY
+    }
+
     private weak var window: NSWindow?
     private let hostView = WindowBrowserHostView(frame: .zero)
     private weak var installedContainerView: NSView?
@@ -2119,7 +2156,60 @@ final class WindowBrowserPortal: NSObject {
         return !isInteractiveSplitDividerDrag(in: window)
     }
 
+    private static func noteInteractiveSplitDividerDragIfNeeded(
+        _ splitView: NSSplitView,
+        window: NSWindow,
+        hostView: WindowBrowserHostView
+    ) {
+        guard splitView.window === window else { return }
+        guard !splitView.isDescendant(of: hostView) else { return }
+        guard (NSEvent.pressedMouseButtons & 1) != 0 else { return }
+        guard let event = NSApp.currentEvent else { return }
+        let now = ProcessInfo.processInfo.systemUptime
+        guard (now - event.timestamp) < 0.1 else { return }
+        guard event.window === window else { return }
+        switch event.type {
+        case .leftMouseDown, .leftMouseDragged:
+            break
+        default:
+            return
+        }
+        guard splitView.arrangedSubviews.count >= 2 else { return }
+
+        let location = splitView.convert(event.locationInWindow, from: nil)
+        let first = splitView.arrangedSubviews[0].frame
+        let second = splitView.arrangedSubviews[1].frame
+        let thickness = splitView.dividerThickness
+        let dividerRect: NSRect
+
+        if splitView.isVertical {
+            guard first.width > 1, second.width > 1 else { return }
+            dividerRect = NSRect(
+                x: max(0, first.maxX),
+                y: 0,
+                width: thickness,
+                height: splitView.bounds.height
+            )
+        } else {
+            guard first.height > 1, second.height > 1 else { return }
+            dividerRect = NSRect(
+                x: 0,
+                y: max(0, first.maxY),
+                width: splitView.bounds.width,
+                height: thickness
+            )
+        }
+
+        let hitRect = dividerRect.insetBy(dx: -5, dy: -5)
+        if dividerHitRectContains(location, rect: hitRect) {
+            window.browserPortalHasInteractiveSplitDividerDrag = true
+        }
+    }
+
     private static func isInteractiveSplitDividerDrag(in window: NSWindow) -> Bool {
+        if window.browserPortalHasInteractiveSplitDividerDrag {
+            return true
+        }
         guard (NSEvent.pressedMouseButtons & 1) != 0 else { return false }
         guard let event = NSApp.currentEvent else { return false }
         let now = ProcessInfo.processInfo.systemUptime
@@ -2155,6 +2245,22 @@ final class WindowBrowserPortal: NSObject {
                 self?.scheduleExternalGeometrySynchronize()
             }
         })
+        geometryObservers.append(center.addObserver(
+            forName: NSSplitView.willResizeSubviewsNotification,
+            object: nil,
+            queue: .main
+        ) { [weak self] notification in
+            MainActor.assumeIsolated {
+                guard let self,
+                      let splitView = notification.object as? NSSplitView,
+                      let window = self.window else { return }
+                Self.noteInteractiveSplitDividerDragIfNeeded(
+                    splitView,
+                    window: window,
+                    hostView: self.hostView
+                )
+            }
+        })
         geometryObservers.append(center.addObserver(
             forName: NSSplitView.didResizeSubviewsNotification,
             object: nil,

Sources/TabManager.swift

@@ -1503,6 +1503,20 @@ class TabManager: ObservableObject {
         }
     }
 
+    private func scheduleInitialWorkspaceGitMetadataRefresh(
+        workspaceId: UUID,
+        panelId: UUID,
+        directory: String
+    ) {
+        scheduleWorkspaceGitMetadataRefresh(
+            workspaceId: workspaceId,
+            panelId: panelId,
+            directory: directory,
+            delays: Self.initialWorkspaceGitProbeDelays,
+            reason: "initial"
+        )
+    }
+
     private func scheduleWorkspaceGitMetadataRefresh(
         workspaceId: UUID,
         panelId: UUID,

cmuxTests/TabManagerUnitTests.swift

@@ -710,8 +710,8 @@ final class TabManagerPullRequestProbeTests: XCTestCase {
             return
         }
 
-        workspace.updatePanelDirectory(panelId: panelId, directory: repoURL.path)
-        workspace.updatePanelGitBranch(panelId: panelId, branch: "feature/sidebar-pr", isDirty: false)
+        manager.updateSurfaceDirectory(tabId: workspace.id, surfaceId: panelId, directory: repoURL.path)
+        manager.updateSurfaceGitBranch(tabId: workspace.id, surfaceId: panelId, branch: "feature/sidebar-pr", isDirty: false)
         workspace.updatePanelPullRequest(
             panelId: panelId,
             number: 1052,