Fix splitter hitbox overlap and terminal scrollbar width resync (#1950)

* test: add splitter and scrollbar regressions

* fix: narrow sidebar overlap and resync terminal width

* test: unwrap pending surface width in scrollbar regression

* fix: restore hosted inspector divider drag path

Author: austinywang

Sources/BrowserWindowPortal.swift

@@ -732,8 +732,8 @@ final class WindowBrowserHostView: NSView {
             return false
         }
 
-        let regionMinX = dividerX - SidebarResizeInteraction.hitWidthPerSide
-        let regionMaxX = dividerX + SidebarResizeInteraction.hitWidthPerSide
+        let regionMinX = dividerX - SidebarResizeInteraction.sidebarSideHitWidth
+        let regionMaxX = dividerX + SidebarResizeInteraction.contentSideHitWidth
         return point.x >= regionMinX && point.x <= regionMaxX
     }
 

Sources/ContentView.swift

@@ -336,11 +336,13 @@ final class SidebarState: ObservableObject {
 }
 
 enum SidebarResizeInteraction {
-    static let handleWidth: CGFloat = 6
-    static let hitInset: CGFloat = 3
+    // Keep a generous drag target inside the sidebar itself, but make the
+    // terminal-side overlap very small so column-0 text selection still wins.
+    static let sidebarSideHitWidth: CGFloat = 6
+    static let contentSideHitWidth: CGFloat = 2
 
-    static var hitWidthPerSide: CGFloat {
-        hitInset + (handleWidth / 2)
+    static var totalHitWidth: CGFloat {
+        sidebarSideHitWidth + contentSideHitWidth
     }
 }
 
@@ -2025,8 +2027,12 @@ struct ContentView: View {
         case divider
     }
 
-    private var sidebarResizerHitWidthPerSide: CGFloat {
-        SidebarResizeInteraction.hitWidthPerSide
+    private var sidebarResizerSidebarHitWidth: CGFloat {
+        SidebarResizeInteraction.sidebarSideHitWidth
+    }
+
+    private var sidebarResizerContentHitWidth: CGFloat {
+        SidebarResizeInteraction.contentSideHitWidth
     }
 
     private func maxSidebarWidth(availableWidth: CGFloat? = nil) -> CGFloat {
@@ -2102,8 +2108,8 @@ struct ContentView: View {
 
     private func dividerBandContains(pointInContent point: NSPoint, contentBounds: NSRect) -> Bool {
         guard point.y >= contentBounds.minY, point.y <= contentBounds.maxY else { return false }
-        let minX = sidebarWidth - sidebarResizerHitWidthPerSide
-        let maxX = sidebarWidth + sidebarResizerHitWidthPerSide
+        let minX = sidebarWidth - sidebarResizerSidebarHitWidth
+        let maxX = sidebarWidth + sidebarResizerContentHitWidth
         return point.x >= minX && point.x <= maxX
     }
 
@@ -2283,7 +2289,7 @@ struct ContentView: View {
         GeometryReader { proxy in
             let totalWidth = max(0, proxy.size.width)
             let dividerX = min(max(sidebarWidth, 0), totalWidth)
-            let leadingWidth = max(0, dividerX - sidebarResizerHitWidthPerSide)
+            let leadingWidth = max(0, dividerX - sidebarResizerSidebarHitWidth)
 
             HStack(spacing: 0) {
                 Color.clear
@@ -2292,7 +2298,7 @@ struct ContentView: View {
 
                 sidebarResizerHandleOverlay(
                     .divider,
-                    width: sidebarResizerHitWidthPerSide * 2,
+                    width: SidebarResizeInteraction.totalHitWidth,
                     availableWidth: totalWidth,
                     accessibilityIdentifier: "SidebarResizer"
                 )

Sources/GhosttyTerminalView.swift

@@ -4468,6 +4468,12 @@ class GhosttyNSView: NSView, NSUserInterfaceValidations {
         updateSurfaceSize(size: size)
     }
 
+#if DEBUG
+    fileprivate func debugPendingSurfaceSize() -> CGSize? {
+        pendingSurfaceSize
+    }
+#endif
+
     /// Force a full size reconciliation for the current bounds.
     /// Keep the drawable-size cache intact so redundant refresh paths do not
     /// reallocate Metal drawables when the pixel size is unchanged.
@@ -7032,6 +7038,17 @@ final class GhosttySurfaceScrollView: NSView {
         ) { [weak self] _ in
             self?.synchronizeScrollView()
         })
+
+        observers.append(NotificationCenter.default.addObserver(
+            forName: NSScroller.preferredScrollerStyleDidChangeNotification,
+            object: nil,
+            // Match AppKit's geometry change immediately so the terminal width
+            // does not stay stuck behind a legacy scrollbar gutter.
+            queue: nil
+        ) { [weak self] _ in
+            self?.handlePreferredScrollerStyleChange()
+        })
+
     }
 
     required init?(coder: NSCoder) {
@@ -8061,6 +8078,10 @@ final class GhosttySurfaceScrollView: NSView {
         surfaceView.debugSimulateFileDrop(paths: paths)
     }
 
+    func debugPendingSurfaceSize() -> CGSize? {
+        surfaceView.debugPendingSurfaceSize()
+    }
+
     func debugRegisteredDropTypes() -> [String] {
         surfaceView.debugRegisteredDropTypes()
     }
@@ -9072,6 +9093,21 @@ final class GhosttySurfaceScrollView: NSView {
         synchronizeScrollView()
     }
 
+    private func handlePreferredScrollerStyleChange() {
+        guard Thread.isMainThread else {
+            DispatchQueue.main.async { [weak self] in
+                self?.handlePreferredScrollerStyleChange()
+            }
+            return
+        }
+
+        // Retile just the scroll view so contentSize reflects the current
+        // scrollbar mode without perturbing viewport origin or hosted view
+        // geometry; the broader reconcile path caused visible content glitches.
+        scrollView.tile()
+        _ = synchronizeCoreSurface()
+    }
+
     private func documentHeight() -> CGFloat {
         let contentHeight = scrollView.contentSize.height
         let cellHeight = surfaceView.cellSize.height

Sources/Panels/BrowserPanelView.swift

@@ -5037,10 +5037,12 @@ struct WebViewRepresentable: NSViewRepresentable {
                 // Origin-only frame churn is common while the surrounding split layout
                 // settles. Reapplying the side-docked inspector at the same size fights
                 // WebKit's own dock layout and shows up as visible flicker.
-                if !isHostedInspectorSideDockActive() &&
-                    !isHostedInspectorDividerDragActive &&
-                    !hasStoredHostedInspectorWidthPreference {
-                    captureHostedInspectorPreferredWidthFromCurrentLayout(reason: "host.layout.sameSize")
+                if !isHostedInspectorDividerDragActive {
+                    if hasStoredHostedInspectorWidthPreference {
+                        reapplyHostedInspectorDividerToStoredWidthIfNeeded(reason: "host.layout.sameSize")
+                    } else if !isHostedInspectorSideDockActive() {
+                        captureHostedInspectorPreferredWidthFromCurrentLayout(reason: "host.layout.sameSize")
+                    }
                 }
                 updateHostedInspectorDockControlAvailabilityIfNeeded(reason: "host.layout.sameSize")
                 notifyGeometryChangedIfNeeded()
@@ -5052,7 +5054,9 @@ struct WebViewRepresentable: NSViewRepresentable {
             lastHostedInspectorLayoutBoundsSize = bounds.size
             if isHostedInspectorSideDockActive() {
                 layoutHostedInspectorSideDockIfNeeded(reason: "host.layout.sideDock")
-            } else if !hasStoredHostedInspectorWidthPreference {
+            } else if hasStoredHostedInspectorWidthPreference {
+                reapplyHostedInspectorDividerToStoredWidthIfNeeded(reason: "host.layout")
+            } else {
                 captureHostedInspectorPreferredWidthFromCurrentLayout(reason: "host.layout")
             }
             updateHostedInspectorDockControlAvailabilityIfNeeded(reason: "host.layout")
@@ -5130,26 +5134,24 @@ struct WebViewRepresentable: NSViewRepresentable {
                 return nil
             }
             if let hostedInspectorHit {
-                let isSideDockHit = isHostedInspectorSideDockHit(hostedInspectorHit)
                 if let nativeHit = nativeHostedInspectorHit(at: point, hostedInspectorHit: hostedInspectorHit) {
 #if DEBUG
                     debugLogHitTest(stage: "hitTest.hostedInspectorNative", point: point, passThrough: false, hitView: nativeHit)
 #endif
-                    if !isSideDockHit ||
-                        (nativeHit !== hostedInspectorHit.inspectorView &&
-                            !hostedInspectorHit.inspectorView.isDescendant(of: nativeHit)) {
+                    if nativeHit !== hostedInspectorHit.inspectorView &&
+                        !hostedInspectorHit.inspectorView.isDescendant(of: nativeHit) {
                         return nativeHit
                     }
                 }
 #if DEBUG
                 debugLogHitTest(
-                    stage: isSideDockHit ? "hitTest.hostedInspectorManual" : "hitTest.hostedInspectorFallback",
+                    stage: "hitTest.hostedInspectorManual",
                     point: point,
                     passThrough: false,
-                    hitView: hostedInspectorHit.inspectorView
+                    hitView: self
                 )
 #endif
-                return isSideDockHit ? self : hostedInspectorHit.inspectorView
+                return self
             }
             let hit = super.hitTest(point)
 #if DEBUG
@@ -5160,8 +5162,7 @@ struct WebViewRepresentable: NSViewRepresentable {
 
         override func mouseDown(with event: NSEvent) {
             let point = convert(event.locationInWindow, from: nil)
-            guard let hostedInspectorHit = hostedInspectorDividerHit(at: point),
-                  isHostedInspectorSideDockHit(hostedInspectorHit) else {
+            guard let hostedInspectorHit = hostedInspectorDividerHit(at: point) else {
                 super.mouseDown(with: event)
                 return
             }
@@ -5258,7 +5259,7 @@ struct WebViewRepresentable: NSViewRepresentable {
                     )
                 )
 #endif
-                layoutHostedInspectorSideDockIfNeeded(reason: "drag.end")
+                reapplyHostedInspectorDividerToStoredWidthIfNeeded(reason: "drag.end")
             }
             super.mouseUp(with: event)
         }
@@ -5273,7 +5274,7 @@ struct WebViewRepresentable: NSViewRepresentable {
             // Pass through a narrow leading-edge band so the shared sidebar divider
             // handle can receive hover/click even when WKWebView is attached here.
             // Keeping this deterministic avoids flicker from dynamic left-edge scans.
-            guard point.x >= 0, point.x <= SidebarResizeInteraction.hitWidthPerSide else {
+            guard point.x >= 0, point.x <= SidebarResizeInteraction.contentSideHitWidth else {
                 return false
             }
             guard let window, let contentView = window.contentView else {
@@ -5495,9 +5496,9 @@ struct WebViewRepresentable: NSViewRepresentable {
                 guard let self else { return }
                 self.hostedInspectorReapplyWorkItem = nil
                 _ = self.promoteHostedInspectorSideDockFromCurrentLayoutIfNeeded()
-                if self.isHostedInspectorSideDockActive() {
+                if self.hasStoredHostedInspectorWidthPreference {
                     self.reapplyHostedInspectorDividerToStoredWidthIfNeeded(reason: reason)
-                } else if !self.hasStoredHostedInspectorWidthPreference {
+                } else {
                     self.captureHostedInspectorPreferredWidthFromCurrentLayout(reason: reason)
                 }
             }
@@ -5558,7 +5559,6 @@ struct WebViewRepresentable: NSViewRepresentable {
         private func reapplyHostedInspectorDividerToStoredWidthIfNeeded(reason: String) {
             guard !isApplyingHostedInspectorLayout else { return }
             guard let hit = hostedInspectorDividerCandidate() else { return }
-            guard isHostedInspectorSideDockHit(hit) else { return }
             guard let preferredWidth = resolvedPreferredHostedInspectorWidth(in: hit.containerView.bounds) else {
                 return
             }

Sources/TerminalWindowPortal.swift

@@ -243,8 +243,8 @@ final class WindowTerminalHostView: NSView {
             return false
         }
 
-        let regionMinX = dividerX - SidebarResizeInteraction.hitWidthPerSide
-        let regionMaxX = dividerX + SidebarResizeInteraction.hitWidthPerSide
+        let regionMinX = dividerX - SidebarResizeInteraction.sidebarSideHitWidth
+        let regionMaxX = dividerX + SidebarResizeInteraction.contentSideHitWidth
         return point.x >= regionMinX && point.x <= regionMaxX
     }
 

cmuxTests/BrowserPanelTests.swift

@@ -547,7 +547,7 @@ final class WindowBrowserHostViewTests: XCTestCase {
 
         XCTAssertLessThanOrEqual(inspectorSplit.arrangedSubviews[0].frame.width, 1.5)
         XCTAssertTrue(
-            abs(dividerPointInHost.x - slot.frame.minX) <= SidebarResizeInteraction.hitWidthPerSide,
+            abs(dividerPointInHost.x - slot.frame.minX) <= 2,
             "Expected collapsed hosted divider to overlap the browser slot leading-edge resizer zone"
         )
 
@@ -905,7 +905,7 @@ final class WindowBrowserHostViewTests: XCTestCase {
         let dividerPointInWindow = slot.convert(dividerPointInSlot, to: nil)
         let dividerPointInHost = host.convert(dividerPointInWindow, from: nil)
 
-        XCTAssertLessThanOrEqual(dividerPointInHost.x - slot.frame.minX, SidebarResizeInteraction.hitWidthPerSide)
+        XCTAssertLessThanOrEqual(dividerPointInHost.x - slot.frame.minX, 2)
         let dividerHit = host.hitTest(dividerPointInHost)
         XCTAssertTrue(
             isInspectorOwnedHit(dividerHit, inspectorView: inspectorView, pageView: pageView),