Fix titlebar text dragging while preserving folder icon drag

Sources/WindowDragHandleView.swift

@@ -1,23 +1,184 @@
 import AppKit
+import Bonsplit
 import SwiftUI
 
+private func windowDragHandleFormatPoint(_ point: NSPoint) -> String {
+    String(format: "(%.1f,%.1f)", point.x, point.y)
+}
+
+private var windowDragSuppressionDepthKey: UInt8 = 0
+
+func beginWindowDragSuppression(window: NSWindow?) -> Int? {
+    guard let window else { return nil }
+    let current = windowDragSuppressionDepth(window: window)
+    let next = current + 1
+    objc_setAssociatedObject(
+        window,
+        &windowDragSuppressionDepthKey,
+        NSNumber(value: next),
+        .OBJC_ASSOCIATION_RETAIN_NONATOMIC
+    )
+    return next
+}
+
+@discardableResult
+func endWindowDragSuppression(window: NSWindow?) -> Int {
+    guard let window else { return 0 }
+    let current = windowDragSuppressionDepth(window: window)
+    let next = max(0, current - 1)
+    if next == 0 {
+        objc_setAssociatedObject(window, &windowDragSuppressionDepthKey, nil, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
+    } else {
+        objc_setAssociatedObject(
+            window,
+            &windowDragSuppressionDepthKey,
+            NSNumber(value: next),
+            .OBJC_ASSOCIATION_RETAIN_NONATOMIC
+        )
+    }
+    return next
+}
+
+func windowDragSuppressionDepth(window: NSWindow?) -> Int {
+    guard let window,
+          let value = objc_getAssociatedObject(window, &windowDragSuppressionDepthKey) as? NSNumber else {
+        return 0
+    }
+    return value.intValue
+}
+
+func isWindowDragSuppressed(window: NSWindow?) -> Bool {
+    windowDragSuppressionDepth(window: window) > 0
+}
+
+/// Temporarily enables window movability for explicit drag-handle drags, then
+/// restores the previous movability state after `body` finishes.
+@discardableResult
+func withTemporaryWindowMovableEnabled(window: NSWindow?, _ body: () -> Void) -> Bool? {
+    guard let window else {
+        body()
+        return nil
+    }
+
+    let previousMovableState = window.isMovable
+    if !previousMovableState {
+        window.isMovable = true
+    }
+    defer {
+        if window.isMovable != previousMovableState {
+            window.isMovable = previousMovableState
+        }
+    }
+
+    body()
+    return previousMovableState
+}
+
+private enum WindowDragHandleHitTestState {
+    static var isResolvingTopHit = false
+}
+
+/// SwiftUI/AppKit hosting wrappers can appear as the top hit even for empty
+/// titlebar space. Treat those as pass-through so explicit sibling checks decide.
+func windowDragHandleShouldTreatTopHitAsPassiveHost(_ view: NSView) -> Bool {
+    let className = String(describing: type(of: view))
+    if className.contains("HostContainerView")
+        || className.contains("AppKitWindowHostingView")
+        || className.contains("NSHostingView") {
+        return true
+    }
+    if let window = view.window, view === window.contentView {
+        return true
+    }
+    return false
+}
+
 /// Returns whether the titlebar drag handle should capture a hit at `point`.
 /// We only claim the hit when no sibling view already handles it, so interactive
 /// controls layered in the titlebar (e.g. proxy folder icon) keep their gestures.
 func windowDragHandleShouldCaptureHit(_ point: NSPoint, in dragHandleView: NSView) -> Bool {
-    guard dragHandleView.bounds.contains(point) else { return false }
-    guard let superview = dragHandleView.superview else { return true }
+    if isWindowDragSuppressed(window: dragHandleView.window) {
+        #if DEBUG
+        let depth = windowDragSuppressionDepth(window: dragHandleView.window)
+        dlog(
+            "titlebar.dragHandle.hitTest capture=false reason=suppressed depth=\(depth) point=\(windowDragHandleFormatPoint(point))"
+        )
+        #endif
+        return false
+    }
+
+    guard dragHandleView.bounds.contains(point) else {
+        #if DEBUG
+        dlog("titlebar.dragHandle.hitTest capture=false reason=outside point=\(windowDragHandleFormatPoint(point))")
+        #endif
+        return false
+    }
+
+    guard let superview = dragHandleView.superview else {
+        #if DEBUG
+        dlog("titlebar.dragHandle.hitTest capture=true reason=noSuperview point=\(windowDragHandleFormatPoint(point))")
+        #endif
+        return true
+    }
+
+    if let window = dragHandleView.window,
+       let contentView = window.contentView,
+       !WindowDragHandleHitTestState.isResolvingTopHit {
+        let pointInWindow = dragHandleView.convert(point, to: nil)
+        let pointInContent = contentView.convert(pointInWindow, from: nil)
+
+        WindowDragHandleHitTestState.isResolvingTopHit = true
+        let topHit = contentView.hitTest(pointInContent)
+        WindowDragHandleHitTestState.isResolvingTopHit = false
+
+        if let topHit {
+            let ownsTopHit = topHit === dragHandleView || topHit.isDescendant(of: dragHandleView)
+            let isPassiveHostHit = windowDragHandleShouldTreatTopHitAsPassiveHost(topHit)
+            #if DEBUG
+            dlog(
+                "titlebar.dragHandle.hitTest capture=\(ownsTopHit) strategy=windowTopHit point=\(windowDragHandleFormatPoint(point)) top=\(type(of: topHit)) passiveHost=\(isPassiveHostHit)"
+            )
+            #endif
+            if ownsTopHit {
+                return true
+            }
+            if !isPassiveHostHit {
+                return false
+            }
+        }
+    }
+
+    #if DEBUG
+    let siblingCount = superview.subviews.count
+    #endif
 
     for sibling in superview.subviews.reversed() {
         guard sibling !== dragHandleView else { continue }
         guard !sibling.isHidden, sibling.alphaValue > 0 else { continue }
 
         let pointInSibling = dragHandleView.convert(point, to: sibling)
-        if sibling.hitTest(pointInSibling) != nil {
+        if let hitView = sibling.hitTest(pointInSibling) {
+            let passiveHostHit = windowDragHandleShouldTreatTopHitAsPassiveHost(hitView)
+            if passiveHostHit {
+                #if DEBUG
+                dlog(
+                    "titlebar.dragHandle.hitTest capture=defer point=\(windowDragHandleFormatPoint(point)) sibling=\(type(of: sibling)) hit=\(type(of: hitView)) passiveHost=true"
+                )
+                #endif
+                continue
+            }
+            #if DEBUG
+            dlog(
+                "titlebar.dragHandle.hitTest capture=false point=\(windowDragHandleFormatPoint(point)) siblingCount=\(siblingCount) sibling=\(type(of: sibling)) hit=\(type(of: hitView)) passiveHost=false"
+            )
+            #endif
             return false
         }
     }
 
+    #if DEBUG
+    dlog("titlebar.dragHandle.hitTest capture=true point=\(windowDragHandleFormatPoint(point)) siblingCount=\(siblingCount)")
+    #endif
     return true
 }
 
@@ -34,9 +195,53 @@ struct WindowDragHandleView: NSViewRepresentable {
     }
 
     private final class DraggableView: NSView {
-        override var mouseDownCanMoveWindow: Bool { true }
+        override var mouseDownCanMoveWindow: Bool { false }
+
         override func hitTest(_ point: NSPoint) -> NSView? {
-            windowDragHandleShouldCaptureHit(point, in: self) ? self : nil
+            let shouldCapture = windowDragHandleShouldCaptureHit(point, in: self)
+            #if DEBUG
+            dlog(
+                "titlebar.dragHandle.hitTestResult capture=\(shouldCapture) point=\(windowDragHandleFormatPoint(point)) window=\(window != nil)"
+            )
+            #endif
+            return shouldCapture ? self : nil
+        }
+
+        override func mouseDown(with event: NSEvent) {
+            #if DEBUG
+            let point = convert(event.locationInWindow, from: nil)
+            let depth = windowDragSuppressionDepth(window: window)
+            dlog(
+                "titlebar.dragHandle.mouseDown point=\(windowDragHandleFormatPoint(point)) clickCount=\(event.clickCount) depth=\(depth)"
+            )
+            #endif
+
+            if event.clickCount >= 2 {
+                window?.zoom(nil)
+                #if DEBUG
+                dlog("titlebar.dragHandle.mouseDownDoubleClick zoom=1")
+                #endif
+                return
+            }
+
+            guard !isWindowDragSuppressed(window: window) else {
+                #if DEBUG
+                dlog("titlebar.dragHandle.mouseDownIgnored reason=suppressed")
+                #endif
+                return
+            }
+
+            if let window {
+                let previousMovableState = withTemporaryWindowMovableEnabled(window: window) {
+                    window.performDrag(with: event)
+                }
+                #if DEBUG
+                let restored = previousMovableState.map { String($0) } ?? "nil"
+                dlog("titlebar.dragHandle.mouseDownComplete restoredMovable=\(restored) nowMovable=\(window.isMovable)")
+                #endif
+            } else {
+                super.mouseDown(with: event)
+            }
         }
     }
 }