make draggable regions work

shell/browser/api/electron_api_browser_window.cc

@@ -82,7 +82,6 @@ BrowserWindow::BrowserWindow(gin::Arguments* args,
   gin::Handle<WebContentsView> web_contents_view =
       WebContentsView::Create(isolate, web_preferences);
   DCHECK(web_contents_view.get());
-  window_->AddDraggableRegionProvider(web_contents_view.get());
 
   // Save a reference of the WebContents.
   gin::Handle<WebContents> web_contents =

shell/browser/api/electron_api_web_contents_view.cc

@@ -7,6 +7,7 @@
 #include "base/no_destructor.h"
 #include "shell/browser/api/electron_api_web_contents.h"
 #include "shell/browser/browser.h"
+#include "shell/browser/native_window.h"
 #include "shell/browser/ui/inspectable_web_contents_view.h"
 #include "shell/browser/web_contents_preferences.h"
 #include "shell/common/gin_converters/gfx_converter.h"
@@ -19,6 +20,7 @@
 #include "ui/base/hit_test.h"
 #include "ui/views/layout/flex_layout_types.h"
 #include "ui/views/view_class_properties.h"
+#include "ui/views/widget/widget.h"
 
 #if BUILDFLAG(IS_MAC)
 #include "shell/browser/ui/cocoa/delayed_native_view_host.h"
@@ -90,6 +92,26 @@ void WebContentsView::WebContentsDestroyed() {
   web_contents_.Reset();
 }
 
+void WebContentsView::OnViewAddedToWidget(views::View* observed_view) {
+  DCHECK_EQ(observed_view, view());
+  views::Widget* widget = view()->GetWidget();
+  auto* native_window = static_cast<NativeWindow*>(
+      widget->GetNativeWindowProperty(electron::kElectronNativeWindowKey));
+  if (!native_window)
+    return;
+  native_window->AddDraggableRegionProvider(this);
+}
+
+void WebContentsView::OnViewRemovedFromWidget(views::View* observed_view) {
+  DCHECK_EQ(observed_view, view());
+  views::Widget* widget = view()->GetWidget();
+  auto* native_window = static_cast<NativeWindow*>(
+      widget->GetNativeWindowProperty(kElectronNativeWindowKey));
+  if (!native_window)
+    return;
+  native_window->RemoveDraggableRegionProvider(this);
+}
+
 // static
 gin::Handle<WebContentsView> WebContentsView::Create(
     v8::Isolate* isolate,

shell/browser/api/electron_api_web_contents_view.h

@@ -47,6 +47,10 @@ class WebContentsView : public View,
   // content::WebContentsObserver:
   void WebContentsDestroyed() override;
 
+  // views::ViewObserver
+  void OnViewAddedToWidget(views::View* view) override;
+  void OnViewRemovedFromWidget(views::View* view) override;
+
  private:
   static gin_helper::WrappableBase* New(gin_helper::Arguments* args);
 

shell/browser/native_window.cc

@@ -84,6 +84,8 @@ gfx::Size GetExpandedWindowSize(const NativeWindow* window, gfx::Size size) {
 
 }  // namespace
 
+const char kElectronNativeWindowKey[] = "__ELECTRON_NATIVE_WINDOW__";
+
 NativeWindow::NativeWindow(const gin_helper::Dictionary& options,
                            NativeWindow* parent)
     : widget_(std::make_unique<views::Widget>()), parent_(parent) {

shell/browser/native_window.h

@@ -49,6 +49,8 @@ class PersistentDictionary;
 
 namespace electron {
 
+extern const char kElectronNativeWindowKey[];
+
 class ElectronMenuModel;
 
 namespace api {

shell/browser/native_window_mac.mm

@@ -248,6 +248,7 @@ NativeWindowMac::NativeWindowMac(const gin_helper::Dictionary& options,
   params.native_widget =
       new ElectronNativeWidgetMac(this, windowType, styleMask, widget());
   widget()->Init(std::move(params));
+  widget()->SetNativeWindowProperty(kElectronNativeWindowKey, this);
   SetCanResize(resizable);
   window_ = static_cast<ElectronNSWindow*>(
       widget()->GetNativeWindow().GetNativeNSWindow());

shell/browser/native_window_views.cc

@@ -280,6 +280,7 @@ NativeWindowViews::NativeWindowViews(const gin_helper::Dictionary& options,
 #endif
 
   widget()->Init(std::move(params));
+  widget()->SetNativeWindowProperty(kElectronNativeWindowKey, this);
   SetCanResize(resizable_);
 
   bool fullscreen = false;