Move viewport actions into an ApplyScroll callback.

third_party/WebKit/Source/core/page/scrolling/ViewportScrollCallback.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/ViewportScrollCallback.h"
+
+#include "core/dom/Document.h"
+#include "core/frame/FrameHost.h"
+#include "core/frame/FrameView.h"
+#include "core/frame/Settings.h"
+#include "core/frame/TopControls.h"
+#include "core/frame/VisualViewport.h"
+#include "core/input/EventHandler.h"
+#include "core/layout/LayoutView.h"
+#include "core/page/scrolling/ScrollState.h"
+#include "platform/geometry/FloatSize.h"
+#include "platform/scroll/ScrollableArea.h"
+
+namespace blink {
+
+ViewportScrollCallback::ViewportScrollCallback(Document& document,
+    FrameHost& frameHost)
+    : m_document(&document)
+    , m_frameHost(&frameHost)
+{
+    // Only the root document can have a viewport scroll callback for now.
+    ASSERT(!document.ownerElement());
+}
+
+ViewportScrollCallback::~ViewportScrollCallback()
+{
+}
+
+DEFINE_TRACE(ViewportScrollCallback)
+{
+    visitor->trace(m_frameHost);
+    visitor->trace(m_document);
+    ScrollStateCallback::trace(visitor);
+}
+
+bool ViewportScrollCallback::shouldScrollTopControls(const FloatSize& delta,
+    ScrollGranularity granularity) const
+{
+    if (granularity != ScrollByPixel && granularity != ScrollByPrecisePixel)
+        return false;
+
+    ScrollableArea* rootFrameViewport = getRootFrameViewport();
+    if (!rootFrameViewport)
+        return false;
+
+    DoublePoint maxScroll = rootFrameViewport->maximumScrollPositionDouble();
+    DoublePoint scrollPosition = rootFrameViewport->scrollPositionDouble();
+
+    // Always give the delta to the top controls if the scroll is in
+    // the direction to show the top controls. If it's in the
+    // direction to hide the top controls, only give the delta to the
+    // top controls when the frame can scroll.
+    return delta.height() < 0 || scrollPosition.y() < maxScroll.y();
+}
+
+void ViewportScrollCallback::handleEvent(ScrollState* state)
+{
+    if (!m_frameHost || !m_document)
+        return;
+
+    TopControls& topControls = m_frameHost->topControls();
+
+    // Scroll top controls.
+    if (state->isBeginning())
+        topControls.scrollBegin();
+
+    FloatSize delta(state->deltaX(), state->deltaY());
+    ScrollGranularity granularity =
+        ScrollGranularity(static_cast<int>(state->deltaGranularity()));
+    FloatSize remainingDelta = delta;
+
+    if (shouldScrollTopControls(delta, granularity))
+        remainingDelta = topControls.scrollBy(delta);
+
+    bool topControlsConsumedScroll = remainingDelta.height() != delta.height();
+
+    // Do the native scroll.
+    ScrollableArea* rootFrameViewport = getRootFrameViewport();
+    if (!rootFrameViewport)
+        return;
+
+    ScrollResult result =
+        rootFrameViewport->userScroll(granularity, remainingDelta);
+
+    // We consider top controls movement to be scrolling.
+    result.didScrollY |= topControlsConsumedScroll;
+
+    // Handle Overscroll.
+    FloatPoint position(state->positionX(), state->positionY());
+    FloatSize velocity(state->velocityX(), state->velocityY());
+
+    m_document->frame()->eventHandler().handleOverscroll(
+        result, position, velocity);
+
+    // The viewport consumes everything.
+    state->consumeDeltaNative(
+        state->deltaX() - result.unusedScrollDeltaX,
+        state->deltaY() - result.unusedScrollDeltaY);
+}
+
+ScrollableArea* ViewportScrollCallback::getRootFrameViewport() const
+{
+    if (!m_document->layoutView())
+        return nullptr;
+
+    FrameView* frameView = m_document->layoutView()->frameView();
+    if (!frameView)
+        return nullptr;
+
+    ScrollableArea* rootFrameViewport = frameView->getScrollableArea();
+    ASSERT(rootFrameViewport);
+
+    return rootFrameViewport;
+}
+
+} // namespace blink