Split RootScrollerController into top-document and child-document classes

third_party/WebKit/Source/core/page/scrolling/TopDocumentRootScrollerController.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/page/scrolling/TopDocumentRootScrollerController.h"
+
+#include "core/dom/Document.h"
+#include "core/dom/Element.h"
+#include "core/frame/FrameHost.h"
+#include "core/frame/FrameView.h"
+#include "core/page/ChromeClient.h"
+#include "core/page/scrolling/OverscrollController.h"
+#include "core/page/scrolling/ViewportScrollCallback.h"
+#include "platform/scroll/ScrollableArea.h"
+
+namespace blink {
+
+// static
+TopDocumentRootScrollerController* TopDocumentRootScrollerController::create(
+    Document& document)
+{
+    return new TopDocumentRootScrollerController(document);
+}
+
+TopDocumentRootScrollerController::TopDocumentRootScrollerController(
+    Document& document)
+    : RootScrollerController(document)
+{
+}
+
+DEFINE_TRACE(TopDocumentRootScrollerController)
+{
+    visitor->trace(m_viewportApplyScroll);
+    visitor->trace(m_currentViewportApplyScrollHost);
+    RootScrollerController::trace(visitor);
+}
+
+void TopDocumentRootScrollerController::updateEffectiveRootScroller()
+{
+    RootScrollerController::updateEffectiveRootScroller();
+    setViewportApplyScrollOnRootScroller();
+}
+
+void TopDocumentRootScrollerController::setViewportApplyScrollOnRootScroller()
+{
+    if (!m_viewportApplyScroll || !effectiveRootScroller())
+        return;
+
+    ScrollableArea* targetScroller =
+        scrollableAreaFor(*effectiveRootScroller());
+
+    if (!targetScroller)
+        return;
+
+    if (m_currentViewportApplyScrollHost)
+        m_currentViewportApplyScrollHost->removeApplyScroll();
+
+    // Use disable-native-scroll since the ViewportScrollCallback needs to
+    // apply scroll actions both before (TopControls) and after (overscroll)
+    // scrolling the element so it will apply scroll to the element itself.
+    effectiveRootScroller()->setApplyScroll(
+        m_viewportApplyScroll, "disable-native-scroll");
+
+    m_currentViewportApplyScrollHost = effectiveRootScroller();
+
+    // Ideally, scroll customization would pass the current element to scroll to
+    // the apply scroll callback but this doesn't happen today so we set it
+    // through a back door here. This is also needed by the
+    // ViewportScrollCallback to swap the target into the layout viewport
+    // in RootFrameViewport.
+    m_viewportApplyScroll->setScroller(targetScroller);
+}
+
+void TopDocumentRootScrollerController::didUpdateCompositing()
+{
+    FrameHost* frameHost = m_document->frameHost();
+
+    // Let the compositor-side counterpart know about this change.
+    if (frameHost)
+        frameHost->chromeClient().registerViewportLayers();
+}
+
+void TopDocumentRootScrollerController::didAttachDocument()
+{
+    FrameHost* frameHost = m_document->frameHost();
+    FrameView* frameView = m_document->view();
+
+    if (!frameHost || !frameView)
+        return;
+
+    RootFrameViewport* rootFrameViewport = frameView->getRootFrameViewport();
+    DCHECK(rootFrameViewport);
+
+    m_viewportApplyScroll = ViewportScrollCallback::create(
+        &frameHost->topControls(),
+        &frameHost->overscrollController(),
+        *rootFrameViewport);
+
+    updateEffectiveRootScroller();
+}
+
+bool TopDocumentRootScrollerController::isViewportScrollCallback(
+    const ScrollStateCallback* callback) const
+{
+    if (!callback)
+        return false;
+
+    return callback == m_viewportApplyScroll.get();
+}
+
+} // namespace blink