Fix browser panel mouse back/forward buttons and middle-click (#131) (#139)

Handle multi-button mouse events in the browser panel's WKWebView:

- Mouse back button (button 3) triggers goBack(), forward button
  (button 4) triggers goForward(), enabling side-button navigation
  on mice like Logitech
- Middle-click (button 2) on a link opens it in a new browser tab
  by hit-testing the click position via JavaScript and routing through
  the existing openLinkInNewTab mechanism

Sources/Panels/BrowserPanelView.swift

@@ -107,6 +107,14 @@ struct BrowserPanelView: View {
         }) { _ in
             onRequestPanelFocus()
         }
+        .onReceive(NotificationCenter.default.publisher(for: .webViewMiddleClickedLink).filter { [weak panel] note in
+            guard let webView = note.object as? CmuxWebView else { return false }
+            return webView === panel?.webView
+        }) { note in
+            if let url = note.userInfo?["url"] as? URL {
+                panel.openLinkInNewTab(url: url)
+            }
+        }
         .onAppear {
             UserDefaults.standard.register(defaults: [
                 BrowserSearchSettings.searchEngineKey: BrowserSearchSettings.defaultSearchEngine.rawValue,

Sources/Panels/CmuxWebView.swift

@@ -43,6 +43,65 @@ final class CmuxWebView: WKWebView {
         super.mouseDown(with: event)
     }
 
+    // MARK: - Mouse back/forward buttons & middle-click
+
+    override func otherMouseDown(with event: NSEvent) {
+        // Button 3 = back, button 4 = forward (multi-button mice like Logitech).
+        // Consume the event so WebKit doesn't handle it.
+        switch event.buttonNumber {
+        case 3:
+            goBack()
+            return
+        case 4:
+            goForward()
+            return
+        default:
+            break
+        }
+        super.otherMouseDown(with: event)
+    }
+
+    override func otherMouseUp(with event: NSEvent) {
+        // Middle-click (button 2) on a link opens it in a new tab.
+        if event.buttonNumber == 2 {
+            let point = convert(event.locationInWindow, from: nil)
+            findLinkAtPoint(point) { [weak self] url in
+                guard let self, let url else { return }
+                NotificationCenter.default.post(
+                    name: .webViewMiddleClickedLink,
+                    object: self,
+                    userInfo: ["url": url]
+                )
+            }
+            return
+        }
+        super.otherMouseUp(with: event)
+    }
+
+    /// Use JavaScript to find the nearest anchor element at the given view-local point.
+    private func findLinkAtPoint(_ point: NSPoint, completion: @escaping (URL?) -> Void) {
+        // WKWebView's coordinate system is flipped (origin top-left for web content).
+        let flippedY = bounds.height - point.y
+        let js = """
+        (() => {
+            let el = document.elementFromPoint(\(point.x), \(flippedY));
+            while (el) {
+                if (el.tagName === 'A' && el.href) return el.href;
+                el = el.parentElement;
+            }
+            return '';
+        })();
+        """
+        evaluateJavaScript(js) { result, _ in
+            guard let href = result as? String, !href.isEmpty,
+                  let url = URL(string: href) else {
+                completion(nil)
+                return
+            }
+            completion(url)
+        }
+    }
+
     // MARK: - Drag-and-drop passthrough
 
     // WKWebView inherently calls registerForDraggedTypes with public.text (and others).

Sources/TabManager.swift

@@ -2489,4 +2489,5 @@ extension Notification.Name {
     static let browserDidFocusAddressBar = Notification.Name("browserDidFocusAddressBar")
     static let browserDidBlurAddressBar = Notification.Name("browserDidBlurAddressBar")
     static let webViewDidReceiveClick = Notification.Name("webViewDidReceiveClick")
+    static let webViewMiddleClickedLink = Notification.Name("webViewMiddleClickedLink")
 }