Fix tab drag never starting on second-click presses

Sources/Bonsplit/Internal/Views/TabBarView.swift

@@ -1962,7 +1962,7 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
     typealias BeginTabDrag = @MainActor (
         _ tabId: UUID,
         _ sourceView: NSView,
-        _ mouseDownEvent: NSEvent,
+        _ dragEvent: NSEvent,
         _ draggingFrame: NSRect,
         _ dragImage: NSImage
     ) -> Bool
@@ -1997,7 +1997,6 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
     final class TabBarBackgroundNSView: NSView, BonsplitTabItemHitRegionProviding {
         private struct PendingTabDrag {
             let tabId: UUID
-            let mouseDownEvent: NSEvent
             let startPoint: NSPoint
             let frame: NSRect
         }
@@ -2179,8 +2178,12 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
 
         private func trackTabMouseDown(_ event: NSEvent) {
             pendingTabDrag = nil
-            guard event.clickCount == 1,
-                  !event.modifierFlags.contains(.control),
+            // Accept any clickCount: AppKit keeps counting presses that land
+            // near the same point inside the double-click interval, so the
+            // common "click to select, then drag" flow arrives as clickCount 2.
+            // A stationary double-click is unaffected because the drag only
+            // begins once the pointer crosses the movement threshold.
+            guard !event.modifierFlags.contains(.control),
                   let window,
                   event.windowNumber == window.windowNumber else {
                 return
@@ -2195,7 +2198,6 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
             }
             pendingTabDrag = PendingTabDrag(
                 tabId: tabId,
-                mouseDownEvent: event,
                 startPoint: point,
                 frame: frame
             )
@@ -2216,15 +2218,21 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
             }
             self.pendingTabDrag = nil
 
-            guard let dragImage = dragImage(for: pendingTabDrag.frame),
+            // Focus/hover can reveal an accessory or scroll the strip between
+            // the press and the threshold event. Refresh the source frame so
+            // AppKit's item and the destination's geometry snapshot agree at
+            // the moment the session starts.
+            let draggingFrame = geometryRegistry?.frame(for: pendingTabDrag.tabId, in: self)
+                ?? pendingTabDrag.frame
+            guard let dragImage = dragImage(for: draggingFrame),
                   let onBeginTabDrag else {
                 return event
             }
             _ = onBeginTabDrag(
                 pendingTabDrag.tabId,
                 self,
-                pendingTabDrag.mouseDownEvent,
-                pendingTabDrag.frame,
+                event,
+                draggingFrame,
                 dragImage
             )
             // SwiftUI already received the mouse-down. Forward the threshold-
@@ -2249,6 +2257,11 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
             return image
         }
 
+        /// Returns whether the pointer is over a native control that owns its
+        /// own gesture. SwiftUI renders static tab titles through AppKit text
+        /// controls too; treating every ``NSControl`` as interactive therefore
+        /// made drag arming depend on title width and renderer details. Only
+        /// controls that can actually consume the press veto the tab source.
         private static func isNativeInteraction(
             at windowPoint: NSPoint,
             in window: NSWindow
@@ -2257,7 +2270,19 @@ struct TabBarDragAndHoverView: NSViewRepresentable {
             let contentPoint = contentView.convert(windowPoint, from: nil)
             guard var candidate = contentView.hitTest(contentPoint) else { return false }
             while true {
-                if candidate is NSControl || candidate is NSTextView {
+                if let button = candidate as? NSButton, button.isEnabled {
+                    return true
+                }
+                if let textField = candidate as? NSTextField, textField.isEditable {
+                    return true
+                }
+                if let textView = candidate as? NSTextView, textView.isEditable {
+                    return true
+                }
+                if let control = candidate as? NSControl,
+                   control.isEnabled,
+                   control.target != nil,
+                   control.action != nil {
                     return true
                 }
                 guard let parent = candidate.superview else { return false }

Tests/BonsplitTests/TabBarDragEventRoutingTests.swift

@@ -19,14 +19,16 @@ import Testing
         let tabId = UUID()
         let geometryRegistry = TabBarItemGeometryRegistry()
         var beganTabId: UUID?
+        var beganEvent: NSEvent?
 
         contentView.addSubview(sourceView)
         sourceView.addSubview(tabView)
         geometryRegistry.register(tabView, for: tabId)
         sourceView.geometryRegistry = geometryRegistry
         sourceView.tabIds = [tabId]
-        sourceView.onBeginTabDrag = { tabId, _, _, _, _ in
+        sourceView.onBeginTabDrag = { tabId, _, event, _, _ in
             beganTabId = tabId
+            beganEvent = event
             return true
         }
         window.makeKeyAndOrderFront(nil)
@@ -45,12 +47,158 @@ import Testing
         #expect(sourceView.handleTabDragEvent(mouseDown) === mouseDown)
         #expect(sourceView.handleTabDragEvent(mouseDragged) === mouseDragged)
         #expect(beganTabId == tabId)
+        #expect(beganEvent === mouseDragged)
+    }
+
+    @Test func secondClickOfDoubleClickStillArmsTabDrag() throws {
+        // Regression (issue 10033): selecting a tab and immediately dragging it
+        // delivers the press with clickCount == 2, because AppKit keeps counting
+        // clicks that land near the same point inside the double-click interval.
+        // Drag arming must accept those presses or the drag silently never starts.
+        let window = NSWindow(
+            contentRect: NSRect(x: 0, y: 0, width: 240, height: 80),
+            styleMask: [.borderless],
+            backing: .buffered,
+            defer: false
+        )
+        defer { window.orderOut(nil) }
+        let contentView = try #require(window.contentView)
+        let sourceView = TabBarDragAndHoverView.TabBarBackgroundNSView(frame: contentView.bounds)
+        let tabView = NSView(frame: NSRect(x: 20, y: 20, width: 120, height: 30))
+        let tabId = UUID()
+        let geometryRegistry = TabBarItemGeometryRegistry()
+        var beganTabId: UUID?
+
+        contentView.addSubview(sourceView)
+        sourceView.addSubview(tabView)
+        geometryRegistry.register(tabView, for: tabId)
+        sourceView.geometryRegistry = geometryRegistry
+        sourceView.tabIds = [tabId]
+        sourceView.onBeginTabDrag = { tabId, _, _, _, _ in
+            beganTabId = tabId
+            return true
+        }
+        window.makeKeyAndOrderFront(nil)
+
+        let mouseDown = try mouseEvent(
+            type: .leftMouseDown,
+            in: sourceView,
+            at: NSPoint(x: 40, y: 35),
+            clickCount: 2
+        )
+        let mouseDragged = try mouseEvent(
+            type: .leftMouseDragged,
+            in: sourceView,
+            at: NSPoint(x: 50, y: 45),
+            clickCount: 2
+        )
+
+        _ = sourceView.handleTabDragEvent(mouseDown)
+        _ = sourceView.handleTabDragEvent(mouseDragged)
+
+        #expect(beganTabId == tabId)
+    }
+
+    @Test func staticTitleControlDoesNotBlockTabDragArming() throws {
+        let window = NSWindow(
+            contentRect: NSRect(x: 0, y: 0, width: 240, height: 80),
+            styleMask: [.borderless],
+            backing: .buffered,
+            defer: false
+        )
+        defer { window.orderOut(nil) }
+        let contentView = try #require(window.contentView)
+        let sourceView = TabBarDragAndHoverView.TabBarBackgroundNSView(frame: contentView.bounds)
+        let tabId = UUID()
+        let geometryRegistry = TabBarItemGeometryRegistry()
+        let tabView = NSView(frame: NSRect(x: 20, y: 20, width: 180, height: 30))
+        let title = NSTextField(labelWithString: "A very wide tab title")
+        title.frame = tabView.bounds.insetBy(dx: 8, dy: 4)
+        var began = false
+
+        contentView.addSubview(sourceView)
+        sourceView.addSubview(tabView)
+        tabView.addSubview(title)
+        geometryRegistry.register(tabView, for: tabId)
+        sourceView.geometryRegistry = geometryRegistry
+        sourceView.tabIds = [tabId]
+        sourceView.onBeginTabDrag = { _, _, _, _, _ in
+            began = true
+            return true
+        }
+        window.makeKeyAndOrderFront(nil)
+
+        let mouseDown = try mouseEvent(
+            type: .leftMouseDown,
+            in: sourceView,
+            at: NSPoint(x: 80, y: 35)
+        )
+        let mouseDragged = try mouseEvent(
+            type: .leftMouseDragged,
+            in: sourceView,
+            at: NSPoint(x: 92, y: 35)
+        )
+
+        _ = sourceView.handleTabDragEvent(mouseDown)
+        _ = sourceView.handleTabDragEvent(mouseDragged)
+
+        #expect(began)
+    }
+
+    @Test func actionableButtonKeepsOwnershipOfTabPress() throws {
+        let window = NSWindow(
+            contentRect: NSRect(x: 0, y: 0, width: 240, height: 80),
+            styleMask: [.borderless],
+            backing: .buffered,
+            defer: false
+        )
+        defer { window.orderOut(nil) }
+        let contentView = try #require(window.contentView)
+        let sourceView = TabBarDragAndHoverView.TabBarBackgroundNSView(frame: contentView.bounds)
+        let tabId = UUID()
+        let geometryRegistry = TabBarItemGeometryRegistry()
+        let tabView = NSView(frame: NSRect(x: 20, y: 20, width: 180, height: 30))
+        let button = NSButton(title: "Close", target: nil, action: nil)
+        button.frame = NSRect(x: 150, y: 4, width: 26, height: 22)
+        var began = false
+
+        contentView.addSubview(sourceView)
+        sourceView.addSubview(tabView)
+        tabView.addSubview(button)
+        geometryRegistry.register(tabView, for: tabId)
+        sourceView.geometryRegistry = geometryRegistry
+        sourceView.tabIds = [tabId]
+        sourceView.onBeginTabDrag = { _, _, _, _, _ in
+            began = true
+            return true
+        }
+        window.makeKeyAndOrderFront(nil)
+
+        let hitPoint = sourceView.convert(NSPoint(x: 183, y: 31), to: nil)
+        #expect(contentView.hitTest(contentView.convert(hitPoint, from: nil)) === button)
+
+        let mouseDown = try mouseEvent(
+            type: .leftMouseDown,
+            in: sourceView,
+            at: NSPoint(x: 183, y: 31)
+        )
+        let mouseDragged = try mouseEvent(
+            type: .leftMouseDragged,
+            in: sourceView,
+            at: NSPoint(x: 195, y: 31)
+        )
+
+        _ = sourceView.handleTabDragEvent(mouseDown)
+        _ = sourceView.handleTabDragEvent(mouseDragged)
+
+        #expect(!began)
     }
 
     private func mouseEvent(
         type: NSEvent.EventType,
         in view: NSView,
-        at point: NSPoint
+        at point: NSPoint,
+        clickCount: Int = 1
     ) throws -> NSEvent {
         let window = try #require(view.window)
         return try #require(NSEvent.mouseEvent(
@@ -61,7 +209,7 @@ import Testing
             windowNumber: window.windowNumber,
             context: nil,
             eventNumber: 0,
-            clickCount: 1,
+            clickCount: clickCount,
             pressure: 1
         ))
     }