feat: add multi BrowserView support to BrowserWindow (#16148)

* feat: add multi BrowserView support to BrowserWindow

Add functions addBrowserView, removeBroserView, getBrowserViews to
BrowserWindow class. Existing API as setBrowserView and
getBrowserView code replaced to use new api inside.

* fix: for lint and osx compile errors

* fix: lint error in test code

* feat: add multi BrowserView support to BrowserWindow

Add functions addBrowserView, removeBroserView, getBrowserViews to
BrowserWindow class. Existing API as setBrowserView and
getBrowserView code replaced to use new api inside.

* fix: for lint and osx compile errors

* fix: lint error in test code

* fix: method to be accessible on mac api impl

* fix: missed function declarations for mac impl

* fix: use base class reset function

atom/browser/api/atom_api_browser_window.cc

@@ -304,7 +304,29 @@ void BrowserWindow::SetBackgroundColor(const std::string& color_name) {
 }
 
 void BrowserWindow::SetBrowserView(v8::Local<v8::Value> value) {
-  TopLevelWindow::SetBrowserView(value);
+  TopLevelWindow::ResetBrowserViews();
+  TopLevelWindow::AddBrowserView(value);
+#if defined(OS_MACOSX)
+  UpdateDraggableRegions(nullptr, draggable_regions_);
+#endif
+}
+
+void BrowserWindow::AddBrowserView(v8::Local<v8::Value> value) {
+  TopLevelWindow::AddBrowserView(value);
+#if defined(OS_MACOSX)
+  UpdateDraggableRegions(nullptr, draggable_regions_);
+#endif
+}
+
+void BrowserWindow::RemoveBrowserView(v8::Local<v8::Value> value) {
+  TopLevelWindow::RemoveBrowserView(value);
+#if defined(OS_MACOSX)
+  UpdateDraggableRegions(nullptr, draggable_regions_);
+#endif
+}
+
+void BrowserWindow::ResetBrowserViews() {
+  TopLevelWindow::ResetBrowserViews();
 #if defined(OS_MACOSX)
   UpdateDraggableRegions(nullptr, draggable_regions_);
 #endif

atom/browser/api/atom_api_browser_window.h

@@ -72,6 +72,9 @@ class BrowserWindow : public TopLevelWindow,
   void Blur() override;
   void SetBackgroundColor(const std::string& color_name) override;
   void SetBrowserView(v8::Local<v8::Value> value) override;
+  void AddBrowserView(v8::Local<v8::Value> value) override;
+  void RemoveBrowserView(v8::Local<v8::Value> value) override;
+  void ResetBrowserViews() override;
   void SetVibrancy(v8::Isolate* isolate, v8::Local<v8::Value> value) override;
 
   // BrowserWindow APIs.

atom/browser/api/atom_api_browser_window_mac.mm

@@ -108,8 +108,10 @@ void BrowserWindow::UpdateDraggableRegions(
         DraggableRegionsToSkRegion(regions), webViewWidth, webViewHeight);
   }
 
-  if (window_->browser_view())
+  auto browser_views = window_->browser_views();
-    window_->browser_view()->UpdateDraggableRegions(drag_exclude_rects);
+  for (NativeBrowserView* view : browser_views) {
+    (view)->UpdateDraggableRegions(drag_exclude_rects);
+  }
 
   // Create and add a ControlRegionView for each region that needs to be
   // excluded from the dragging.

atom/browser/api/atom_api_top_level_window.cc

@@ -159,7 +159,7 @@ void TopLevelWindow::OnWindowClosed() {
   Emit("closed");
 
   RemoveFromParentChildWindows();
-  ResetBrowserView();
+  TopLevelWindow::ResetBrowserViews();
 
   // Destroy the native class when window is closed.
   base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE, GetDestroyClosure());
@@ -294,6 +294,7 @@ void TopLevelWindow::OnWindowMessage(UINT message,
 #endif
 
 void TopLevelWindow::SetContentView(mate::Handle<View> view) {
+  ResetBrowserViews();
   content_view_.Reset(isolate(), view.ToV8());
   window_->SetContentView(view->view());
 }
@@ -681,18 +682,37 @@ void TopLevelWindow::SetParentWindow(v8::Local<v8::Value> value,
 }
 
 void TopLevelWindow::SetBrowserView(v8::Local<v8::Value> value) {
-  ResetBrowserView();
+  ResetBrowserViews();
+  AddBrowserView(value);
+}
 
+void TopLevelWindow::AddBrowserView(v8::Local<v8::Value> value) {
   mate::Handle<BrowserView> browser_view;
-  if (value->IsNull() || value->IsUndefined()) {
+  if (value->IsObject() &&
-    window_->SetBrowserView(nullptr);
+      mate::ConvertFromV8(isolate(), value, &browser_view)) {
-  } else if (mate::ConvertFromV8(isolate(), value, &browser_view)) {
+    auto get_that_view = browser_views_.find(browser_view->weak_map_id());
-    window_->SetBrowserView(browser_view->view());
+    if (get_that_view == browser_views_.end()) {
-    browser_view->web_contents()->SetOwnerWindow(window_.get());
+      window_->AddBrowserView(browser_view->view());
-    browser_view_.Reset(isolate(), value);
+      browser_view->web_contents()->SetOwnerWindow(window_.get());
+      browser_views_[browser_view->weak_map_id()].Reset(isolate(), value);
+    }
   }
 }
 
+void TopLevelWindow::RemoveBrowserView(v8::Local<v8::Value> value) {
+  mate::Handle<BrowserView> browser_view;
+  if (value->IsObject() &&
+      mate::ConvertFromV8(isolate(), value, &browser_view)) {
+    auto get_that_view = browser_views_.find(browser_view->weak_map_id());
+    if (get_that_view != browser_views_.end()) {
+      window_->RemoveBrowserView(browser_view->view());
+      browser_view->web_contents()->SetOwnerWindow(nullptr);
+
+      (*get_that_view).second.Reset(isolate(), value);
+      browser_views_.erase(get_that_view);
+    }
+  }
+}
 v8::Local<v8::Value> TopLevelWindow::GetNativeWindowHandle() {
   // TODO(MarshallOfSound): Replace once
   // https://chromium-review.googlesource.com/c/chromium/src/+/1253094/ has
@@ -847,12 +867,29 @@ std::vector<v8::Local<v8::Object>> TopLevelWindow::GetChildWindows() const {
   return child_windows_.Values(isolate());
 }
 
-v8::Local<v8::Value> TopLevelWindow::GetBrowserView() const {
+v8::Local<v8::Value> TopLevelWindow::GetBrowserView(
-  if (browser_view_.IsEmpty()) {
+    mate::Arguments* args) const {
+  if (browser_views_.size() == 0) {
+    return v8::Null(isolate());
+  } else if (browser_views_.size() == 1) {
+    auto first_view = browser_views_.begin();
+    return v8::Local<v8::Value>::New(isolate(), (*first_view).second);
+  } else {
+    args->ThrowError(
+        "BrowserWindow have multiple BrowserViews, "
+        "Use getBrowserViews() instead");
     return v8::Null(isolate());
   }
+}
 
-  return v8::Local<v8::Value>::New(isolate(), browser_view_);
+std::vector<v8::Local<v8::Value>> TopLevelWindow::GetBrowserViews() const {
+  std::vector<v8::Local<v8::Value>> ret;
+
+  for (auto const& views_iter : browser_views_) {
+    ret.push_back(v8::Local<v8::Value>::New(isolate(), views_iter.second));
+  }
+
+  return ret;
 }
 
 bool TopLevelWindow::IsModal() const {
@@ -944,17 +981,21 @@ int32_t TopLevelWindow::GetID() const {
   return weak_map_id();
 }
 
-void TopLevelWindow::ResetBrowserView() {
+void TopLevelWindow::ResetBrowserViews() {
-  if (browser_view_.IsEmpty())
+  for (auto& item : browser_views_) {
-    return;
+    mate::Handle<BrowserView> browser_view;
+    if (mate::ConvertFromV8(isolate(),
+                            v8::Local<v8::Value>::New(isolate(), item.second),
+                            &browser_view) &&
+        !browser_view.IsEmpty()) {
+      window_->RemoveBrowserView(browser_view->view());
+      browser_view->web_contents()->SetOwnerWindow(nullptr);
+    }
 
-  mate::Handle<BrowserView> browser_view;
+    item.second.Reset();
-  if (mate::ConvertFromV8(isolate(), GetBrowserView(), &browser_view) &&
-      !browser_view.IsEmpty()) {
-    browser_view->web_contents()->SetOwnerWindow(nullptr);
   }
 
-  browser_view_.Reset();
+  browser_views_.clear();
 }
 
 void TopLevelWindow::RemoveFromParentChildWindows() {
@@ -1064,6 +1105,8 @@ void TopLevelWindow::BuildPrototype(v8::Isolate* isolate,
       .SetMethod("setMenu", &TopLevelWindow::SetMenu)
       .SetMethod("setParentWindow", &TopLevelWindow::SetParentWindow)
       .SetMethod("setBrowserView", &TopLevelWindow::SetBrowserView)
+      .SetMethod("addBrowserView", &TopLevelWindow::AddBrowserView)
+      .SetMethod("removeBrowserView", &TopLevelWindow::RemoveBrowserView)
       .SetMethod("getNativeWindowHandle",
                  &TopLevelWindow::GetNativeWindowHandle)
       .SetMethod("setProgressBar", &TopLevelWindow::SetProgressBar)
@@ -1101,6 +1144,7 @@ void TopLevelWindow::BuildPrototype(v8::Isolate* isolate,
       .SetMethod("getParentWindow", &TopLevelWindow::GetParentWindow)
       .SetMethod("getChildWindows", &TopLevelWindow::GetChildWindows)
       .SetMethod("getBrowserView", &TopLevelWindow::GetBrowserView)
+      .SetMethod("getBrowserViews", &TopLevelWindow::GetBrowserViews)
       .SetMethod("isModal", &TopLevelWindow::IsModal)
       .SetMethod("setThumbarButtons", &TopLevelWindow::SetThumbarButtons)
 #if defined(TOOLKIT_VIEWS)

atom/browser/api/atom_api_top_level_window.h

@@ -165,6 +165,10 @@ class TopLevelWindow : public mate::TrackableObject<TopLevelWindow>,
   void SetMenu(v8::Isolate* isolate, v8::Local<v8::Value> menu);
   void SetParentWindow(v8::Local<v8::Value> value, mate::Arguments* args);
   virtual void SetBrowserView(v8::Local<v8::Value> value);
+  virtual void AddBrowserView(v8::Local<v8::Value> value);
+  virtual void RemoveBrowserView(v8::Local<v8::Value> value);
+  virtual std::vector<v8::Local<v8::Value>> GetBrowserViews() const;
+  virtual void ResetBrowserViews();
   v8::Local<v8::Value> GetNativeWindowHandle();
   void SetProgressBar(double progress, mate::Arguments* args);
   void SetOverlayIcon(const gfx::Image& overlay,
@@ -195,7 +199,7 @@ class TopLevelWindow : public mate::TrackableObject<TopLevelWindow>,
   v8::Local<v8::Value> GetContentView() const;
   v8::Local<v8::Value> GetParentWindow() const;
   std::vector<v8::Local<v8::Object>> GetChildWindows() const;
-  v8::Local<v8::Value> GetBrowserView() const;
+  v8::Local<v8::Value> GetBrowserView(mate::Arguments* args) const;
   bool IsModal() const;
 
   // Extra APIs added in JS.
@@ -238,7 +242,7 @@ class TopLevelWindow : public mate::TrackableObject<TopLevelWindow>,
 #endif
 
   v8::Global<v8::Value> content_view_;
-  v8::Global<v8::Value> browser_view_;
+  std::map<int32_t, v8::Global<v8::Value>> browser_views_;
   v8::Global<v8::Value> menu_;
   v8::Global<v8::Value> parent_window_;
   KeyWeakMap<int> child_windows_;

atom/browser/native_window.h

@@ -5,6 +5,7 @@
 #ifndef ATOM_BROWSER_NATIVE_WINDOW_H_
 #define ATOM_BROWSER_NATIVE_WINDOW_H_
 
+#include <list>
 #include <map>
 #include <memory>
 #include <string>
@@ -155,7 +156,8 @@ class NativeWindow : public base::SupportsUserData,
   virtual void SetFocusable(bool focusable);
   virtual void SetMenu(AtomMenuModel* menu);
   virtual void SetParentWindow(NativeWindow* parent);
-  virtual void SetBrowserView(NativeBrowserView* browser_view) = 0;
+  virtual void AddBrowserView(NativeBrowserView* browser_view) = 0;
+  virtual void RemoveBrowserView(NativeBrowserView* browser_view) = 0;
   virtual gfx::NativeView GetNativeView() const = 0;
   virtual gfx::NativeWindow GetNativeWindow() const = 0;
   virtual gfx::AcceleratedWidget GetAcceleratedWidget() const = 0;
@@ -286,10 +288,11 @@ class NativeWindow : public base::SupportsUserData,
   bool transparent() const { return transparent_; }
   bool enable_larger_than_screen() const { return enable_larger_than_screen_; }
 
-  NativeBrowserView* browser_view() const { return browser_view_; }
   NativeWindow* parent() const { return parent_; }
   bool is_modal() const { return is_modal_; }
 
+  std::list<NativeBrowserView*> browser_views() const { return browser_views_; }
+
  protected:
   NativeWindow(const mate::Dictionary& options, NativeWindow* parent);
 
@@ -298,8 +301,13 @@ class NativeWindow : public base::SupportsUserData,
   const views::Widget* GetWidget() const override;
 
   void set_content_view(views::View* view) { content_view_ = view; }
-  void set_browser_view(NativeBrowserView* browser_view) {
+
-    browser_view_ = browser_view;
+  void add_browser_view(NativeBrowserView* browser_view) {
+    browser_views_.push_back(browser_view);
+  }
+  void remove_browser_view(NativeBrowserView* browser_view) {
+    browser_views_.remove_if(
+        [&browser_view](NativeBrowserView* n) { return (n == browser_view); });
   }
 
  private:
@@ -340,7 +348,7 @@ class NativeWindow : public base::SupportsUserData,
   bool is_modal_ = false;
 
   // The browser view layer.
-  NativeBrowserView* browser_view_ = nullptr;
+  std::list<NativeBrowserView*> browser_views_;
 
   // Observers of this window.
   base::ObserverList<NativeWindowObserver> observers_;

atom/browser/native_window_mac.h

@@ -102,7 +102,8 @@ class NativeWindowMac : public NativeWindow {
   bool IsDocumentEdited() override;
   void SetIgnoreMouseEvents(bool ignore, bool forward) override;
   void SetContentProtection(bool enable) override;
-  void SetBrowserView(NativeBrowserView* browser_view) override;
+  void AddBrowserView(NativeBrowserView* browser_view) override;
+  void RemoveBrowserView(NativeBrowserView* browser_view) override;
   void SetParentWindow(NativeWindow* parent) override;
   gfx::NativeView GetNativeView() const override;
   gfx::NativeWindow GetNativeWindow() const override;

atom/browser/native_window_mac.mm

@@ -1069,22 +1069,16 @@ void NativeWindowMac::SetContentProtection(bool enable) {
       setSharingType:enable ? NSWindowSharingNone : NSWindowSharingReadOnly];
 }
 
-void NativeWindowMac::SetBrowserView(NativeBrowserView* view) {
+void NativeWindowMac::AddBrowserView(NativeBrowserView* view) {
   [CATransaction begin];
   [CATransaction setDisableActions:YES];
 
-  if (browser_view()) {
-    [browser_view()->GetInspectableWebContentsView()->GetNativeView()
-            removeFromSuperview];
-    set_browser_view(nullptr);
-  }
-
   if (!view) {
     [CATransaction commit];
     return;
   }
 
-  set_browser_view(view);
+  add_browser_view(view);
   auto* native_view = view->GetInspectableWebContentsView()->GetNativeView();
   [[window_ contentView] addSubview:native_view
                          positioned:NSWindowAbove
@@ -1094,6 +1088,21 @@ void NativeWindowMac::SetBrowserView(NativeBrowserView* view) {
   [CATransaction commit];
 }
 
+void NativeWindowMac::RemoveBrowserView(NativeBrowserView* view) {
+  [CATransaction begin];
+  [CATransaction setDisableActions:YES];
+
+  if (!view) {
+    [CATransaction commit];
+    return;
+  }
+
+  [view->GetInspectableWebContentsView()->GetNativeView() removeFromSuperview];
+  remove_browser_view(view);
+
+  [CATransaction commit];
+}
+
 void NativeWindowMac::SetParentWindow(NativeWindow* parent) {
   InternalSetParentWindow(parent, IsVisible());
 }

atom/browser/native_window_views.cc

@@ -315,11 +315,6 @@ NativeWindowViews::~NativeWindowViews() {
 void NativeWindowViews::SetContentView(views::View* view) {
   if (content_view()) {
     root_view_->RemoveChildView(content_view());
-    if (browser_view()) {
-      content_view()->RemoveChildView(
-          browser_view()->GetInspectableWebContentsView()->GetView());
-      set_browser_view(nullptr);
-    }
   }
   set_content_view(view);
   focused_view_ = view;
@@ -960,27 +955,33 @@ void NativeWindowViews::SetMenu(AtomMenuModel* menu_model) {
   }
 }
 
-void NativeWindowViews::SetBrowserView(NativeBrowserView* view) {
+void NativeWindowViews::AddBrowserView(NativeBrowserView* view) {
   if (!content_view())
     return;
 
-  if (browser_view()) {
-    content_view()->RemoveChildView(
-        browser_view()->GetInspectableWebContentsView()->GetView());
-    set_browser_view(nullptr);
-  }
-
   if (!view) {
     return;
   }
 
-  // Add as child of the main web view to avoid (0, 0) origin from overlapping
+  add_browser_view(view);
-  // with menu bar.
+
-  set_browser_view(view);
   content_view()->AddChildView(
       view->GetInspectableWebContentsView()->GetView());
 }
 
+void NativeWindowViews::RemoveBrowserView(NativeBrowserView* view) {
+  if (!content_view())
+    return;
+
+  if (!view) {
+    return;
+  }
+
+  content_view()->RemoveChildView(
+      view->GetInspectableWebContentsView()->GetView());
+  remove_browser_view(view);
+}
+
 void NativeWindowViews::SetParentWindow(NativeWindow* parent) {
   NativeWindow::SetParentWindow(parent);
 
@@ -1175,6 +1176,26 @@ void NativeWindowViews::OnWidgetActivationChanged(views::Widget* changed_widget,
   root_view_->ResetAltState();
 }
 
+void NativeWindowViews::AutoresizeBrowserView(int width_delta,
+                                              int height_delta,
+                                              NativeBrowserView* browser_view) {
+  const auto flags =
+      static_cast<NativeBrowserViewViews*>(browser_view)->GetAutoResizeFlags();
+  if (!(flags & kAutoResizeWidth)) {
+    width_delta = 0;
+  }
+  if (!(flags & kAutoResizeHeight)) {
+    height_delta = 0;
+  }
+  if (height_delta || width_delta) {
+    auto* view = browser_view->GetInspectableWebContentsView()->GetView();
+    auto new_view_size = view->size();
+    new_view_size.set_width(new_view_size.width() + width_delta);
+    new_view_size.set_height(new_view_size.height() + height_delta);
+    view->SetSize(new_view_size);
+  }
+}
+
 void NativeWindowViews::OnWidgetBoundsChanged(views::Widget* changed_widget,
                                               const gfx::Rect& bounds) {
   if (changed_widget != widget())
@@ -1184,23 +1205,10 @@ void NativeWindowViews::OnWidgetBoundsChanged(views::Widget* changed_widget,
   // handle minimized windows on Windows.
   const auto new_bounds = GetBounds();
   if (widget_size_ != new_bounds.size()) {
-    if (browser_view()) {
+    int width_delta = new_bounds.width() - widget_size_.width();
-      const auto flags = static_cast<NativeBrowserViewViews*>(browser_view())
+    int height_delta = new_bounds.height() - widget_size_.height();
-                             ->GetAutoResizeFlags();
+    for (NativeBrowserView* item : browser_views()) {
-      int width_delta = 0;
+      AutoresizeBrowserView(width_delta, height_delta, item);
-      int height_delta = 0;
-      if (flags & kAutoResizeWidth) {
-        width_delta = new_bounds.width() - widget_size_.width();
-      }
-      if (flags & kAutoResizeHeight) {
-        height_delta = new_bounds.height() - widget_size_.height();
-      }
-
-      auto* view = browser_view()->GetInspectableWebContentsView()->GetView();
-      auto new_view_size = view->size();
-      new_view_size.set_width(new_view_size.width() + width_delta);
-      new_view_size.set_height(new_view_size.height() + height_delta);
-      view->SetSize(new_view_size);
     }
 
     NotifyWindowResize();

atom/browser/native_window_views.h

@@ -112,7 +112,8 @@ class NativeWindowViews : public NativeWindow,
   void SetContentProtection(bool enable) override;
   void SetFocusable(bool focusable) override;
   void SetMenu(AtomMenuModel* menu_model) override;
-  void SetBrowserView(NativeBrowserView* browser_view) override;
+  void AddBrowserView(NativeBrowserView* browser_view) override;
+  void RemoveBrowserView(NativeBrowserView* browser_view) override;
   void SetParentWindow(NativeWindow* parent) override;
   gfx::NativeView GetNativeView() const override;
   gfx::NativeWindow GetNativeWindow() const override;
@@ -157,7 +158,9 @@ class NativeWindowViews : public NativeWindow,
   void OnWidgetActivationChanged(views::Widget* widget, bool active) override;
   void OnWidgetBoundsChanged(views::Widget* widget,
                              const gfx::Rect& bounds) override;
-
+  void AutoresizeBrowserView(int width_delta,
+                             int height_delta,
+                             NativeBrowserView* browser_view);
   // views::WidgetDelegate:
   void DeleteDelegate() override;
   views::View* GetInitiallyFocusedView() override;

docs/api/browser-window.md

@@ -1601,11 +1601,29 @@ removed in future Electron releases.
 
 #### `win.setBrowserView(browserView)` _Experimental_
 
-* `browserView` [BrowserView](browser-view.md)
+* `browserView` [BrowserView](browser-view.md). Attach browserView to win.
+If there is some other browserViews was attached they will be removed from
+this window.  
 
 #### `win.getBrowserView()` _Experimental_
 
-Returns `BrowserView | null` - an attached BrowserView. Returns `null` if none is attached.
+Returns `BrowserView | null` - an BrowserView what is attached. Returns `null`
+if none is attached. Throw error if multiple BrowserViews is attached.
+
+#### `win.addBrowserView(browserView)` _Experimental_
+
+* `browserView` [BrowserView](browser-view.md)
+
+Replacement API for setBrowserView supporting work with multi browser views.
+
+#### `win.removeBrowserView(browserView)` _Experimental_
+
+* `browserView` [BrowserView](browser-view.md)
+
+#### `win.getBrowserViews()` _Experimental_
+
+Returns array of `BrowserView` what was an attached with addBrowserView
+or setBrowserView.
 
 **Note:** The BrowserView API is currently experimental and may change or be
 removed in future Electron releases.

spec/api-browser-view-spec.js

@@ -132,6 +132,54 @@ describe('BrowserView module', () => {
     })
   })
 
+  describe('BrowserWindow.addBrowserView()', () => {
+    it('does not throw for valid args', () => {
+      let view1 = new BrowserView()
+      w.addBrowserView(view1)
+      let view2 = new BrowserView()
+      w.addBrowserView(view2)
+      view1.destroy()
+      view1 = null
+      view2.destroy()
+      view2 = null
+    })
+    it('does not throw if called multiple times with same view', () => {
+      view = new BrowserView()
+      w.addBrowserView(view)
+      w.addBrowserView(view)
+      w.addBrowserView(view)
+    })
+  })
+
+  describe('BrowserWindow.removeBrowserView()', () => {
+    it('does not throw if called multiple times with same view', () => {
+      view = new BrowserView()
+      w.addBrowserView(view)
+      w.removeBrowserView(view)
+      w.removeBrowserView(view)
+    })
+  })
+
+  describe('BrowserWindow.getBrowserViews()', () => {
+    it('returns same views as was added', () => {
+      let view1 = new BrowserView()
+      w.addBrowserView(view1)
+      let view2 = new BrowserView()
+      w.addBrowserView(view2)
+
+      expect(view1.id).to.be.not.null()
+      const views = w.getBrowserViews()
+      expect(views.length).to.equal(2)
+      expect(views[0].webContents.id).to.equal(view1.webContents.id)
+      expect(views[1].webContents.id).to.equal(view2.webContents.id)
+
+      view1.destroy()
+      view1 = null
+      view2.destroy()
+      view2 = null
+    })
+  })
+
   describe('BrowserView.webContents.getOwnerBrowserWindow()', () => {
     it('points to owning window', () => {
       view = new BrowserView()