Remove the native window hardware acceleration support for widgets.

This experiment served its purpose and is now more often broken
than useful.

Change-Id: I73ea68c99dedcc8a3fe9004d130518daf146b493
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>

lib/web_contents_adapter_client.h

@@ -74,8 +74,7 @@ class QWEBENGINE_EXPORT WebContentsAdapterClient {
 public:
     enum CompositingMode {
         NoCompositing,
-        DelegatedCompositing,
-        ForcedGpuProcessCompositing
+        DelegatedCompositing
     };
 
     // This must match window_open_disposition_list.h.

lib/web_contents_view_qt.cpp

@@ -76,8 +76,6 @@ content::RenderWidgetHostView* WebContentsViewQt::CreateViewForPopupWidget(conte
     WebContentsAdapterClient::CompositingMode compositingMode = WebContentsAdapterClient::NoCompositing;
     if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableDelegatedRenderer))
         compositingMode = WebContentsAdapterClient::DelegatedCompositing;
-    else if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kForceCompositingMode))
-        compositingMode = WebContentsAdapterClient::ForcedGpuProcessCompositing;
 
     Q_ASSERT(m_factoryClient);
     view->setDelegate(m_factoryClient->CreateRenderWidgetHostViewQtDelegate(view, compositingMode));

lib/widgets/Api/qwebenginepage.cpp

@@ -60,7 +60,8 @@ QWebEnginePagePrivate::~QWebEnginePagePrivate()
 
 RenderWidgetHostViewQtDelegate *QWebEnginePagePrivate::CreateRenderWidgetHostViewQtDelegate(RenderWidgetHostViewQtDelegateClient *client, CompositingMode mode)
 {
-    return new RenderWidgetHostViewQtDelegateWidget(client, mode);
+    Q_UNUSED(mode);
+    return new RenderWidgetHostViewQtDelegateWidget(client);
 }
 
 void QWebEnginePagePrivate::titleChanged(const QString &title)

lib/widgets/render_widget_host_view_qt_delegate_widget.cpp

@@ -51,7 +51,7 @@
 #include <QWindow>
 #include <QtWidgets/QApplication>
 
-RenderWidgetHostViewQtDelegateWidget::RenderWidgetHostViewQtDelegateWidget(RenderWidgetHostViewQtDelegateClient *client, WebContentsAdapterClient::CompositingMode mode, QWidget *parent)
+RenderWidgetHostViewQtDelegateWidget::RenderWidgetHostViewQtDelegateWidget(RenderWidgetHostViewQtDelegateClient *client, QWidget *parent)
     : QWidget(parent)
     , m_client(client)
 {
@@ -59,21 +59,6 @@ RenderWidgetHostViewQtDelegateWidget::RenderWidgetHostViewQtDelegateWidget(Rende
     setMouseTracking(true);
     setAttribute(Qt::WA_AcceptTouchEvents);
     setAttribute(Qt::WA_OpaquePaintEvent);
-
-#if defined(Q_OS_LINUX)
-    // FOR TESTING ONLY, use at your own risks.
-    // Supporting this properly on all platforms would require duplicating
-    // many tricks done by RenderWidgetHostView[Win|Mac].
-    if (mode == WebContentsAdapterClient::ForcedGpuProcessCompositing) {
-        // This sets Qt::WA_NativeWindow and force a native window creation
-        // that we can give to the GPU process for it to render directly
-        // on through windowHandle().
-        winId();
-        // This makes sure that we won't try to paint the regular backing store
-        // on the window at the same time as the compositor.
-        setUpdatesEnabled(false);
-    }
-#endif
 }
 
 void RenderWidgetHostViewQtDelegateWidget::initAsChild(WebContentsAdapterClient* container)
@@ -124,8 +109,8 @@ bool RenderWidgetHostViewQtDelegateWidget::isVisible() const
 
 WId RenderWidgetHostViewQtDelegateWidget::nativeWindowIdForCompositor() const
 {
-    QWindow* window = QWidget::windowHandle();
-    return window ? window->winId() : 0;
+    // The QtWidgets API doesn't support hardware acceleration.
+    return 0;
 }
 
 QWindow* RenderWidgetHostViewQtDelegateWidget::window() const

lib/widgets/render_widget_host_view_qt_delegate_widget.h

@@ -56,7 +56,7 @@ QT_END_NAMESPACE
 class RenderWidgetHostViewQtDelegateWidget : public QWidget, public RenderWidgetHostViewQtDelegate
 {
 public:
-    RenderWidgetHostViewQtDelegateWidget(RenderWidgetHostViewQtDelegateClient *client, WebContentsAdapterClient::CompositingMode mode, QWidget *parent = 0);
+    RenderWidgetHostViewQtDelegateWidget(RenderWidgetHostViewQtDelegateClient *client, QWidget *parent = 0);
 
     virtual void initAsChild(WebContentsAdapterClient* container);
     virtual void initAsPopup(const QRect&);