Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.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/frame/ScrollAndScaleEmulator.h"
+
+#include "core/frame/Frame.h"
+#include "core/frame/FrameHost.h"
+#include "core/frame/FrameView.h"
+#include "core/frame/PageScaleConstraintsSet.h"
+#include "core/frame/Settings.h"
+#include "core/frame/VisualViewport.h"
+#include "core/layout/compositing/PaintLayerCompositor.h"
+#include "core/page/Page.h"
+#include "core/page/scrolling/ScrollingCoordinator.h"
+#include "platform/geometry/FloatSize.h"
+
+namespace blink {
+
+// static
+ScrollAndScaleEmulator* ScrollAndScaleEmulator::create(FrameHost* frameHost)
+{
+    DCHECK(frameHost->page().mainFrame());
+    DCHECK(frameHost->page().mainFrame()->isLocalFrame());
+
+    return new ScrollAndScaleEmulator(frameHost);
+}
+
+DEFINE_TRACE(ScrollAndScaleEmulator)
+{
+    visitor->trace(m_frameHost);
+}
+
+void ScrollAndScaleEmulator::update(const IntPoint& framePosition, const DoublePoint& visualViewportPosition, float pageScale)
+{
+    bool changed = false;
+
+    if (m_framePosition != framePosition) {
+        m_framePosition = framePosition;
+        changed = true;
+    }
+
+    if (m_visualViewportPosition != visualViewportPosition) {
+        m_visualViewportPosition = visualViewportPosition;
+        changed = true;
+    }
+
+    if (m_pageScale != pageScale) {
+        m_pageScale = pageScale;
+        changed = true;
+    }
+
+    if (changed) {
+        if (FrameView* view = m_frameHost->page().deprecatedLocalMainFrame()->view())
+            view->setScrollAndScaleEmulator(this);
+        m_frameHost->setUserAgentPageScaleConstraints(pageScaleConstraints());
+        m_frameHost->visualViewport().setScrollAndScaleEmulator(this);
+    }
+}
+
+void ScrollAndScaleEmulator::clear()
+{
+    setThreadedScrollingEnabled(m_originalThreadedScrollingEnabled);
+    if (FrameView* view = m_frameHost->page().deprecatedLocalMainFrame()->view())
+        view->setScrollAndScaleEmulator(nullptr);
+    m_frameHost->setUserAgentPageScaleConstraints(m_originalPageScaleConstraints);
+    m_frameHost->visualViewport().setScrollAndScaleEmulator(nullptr);
+
+    m_framePosition = IntPoint(-1, -1);
+    m_visualViewportPosition = DoublePoint(-1, -1);
+    m_pageScale = 0;
+    m_frameHost = nullptr;
+}
+
+IntPoint ScrollAndScaleEmulator::applyFramePositionOverride(const IntPoint& position)
+{
+    return applyPositionOverride(position, m_framePosition);
+}
+
+DoublePoint ScrollAndScaleEmulator::applyVisualViewportPositionOverride(const DoublePoint& position)
+{
+    return applyPositionOverride(position, m_visualViewportPosition);
+}
+
+IntSize ScrollAndScaleEmulator::mainFrameSize(const IntSize& webViewSize)
+{
+    // We may have overridden the minimum scale in the user-agent constraints,
+    // so reconstruct the original constraints before computing the frame size.
+    PageScaleConstraintsSet constraints = m_frameHost->pageScaleConstraintsSet();
+    constraints.setUserAgentConstraints(m_originalPageScaleConstraints);
+    constraints.computeFinalConstraints();
+
+    FloatSize frameSize(webViewSize);
+    frameSize.scale(1 / constraints.finalConstraints().minimumScale);
+    return expandedIntSize(frameSize);
+}
+
+ScrollAndScaleEmulator::ScrollAndScaleEmulator(FrameHost* frameHost)
+    : m_framePosition(IntPoint(-1, -1))
+    , m_visualViewportPosition(DoublePoint(-1, -1))
+    , m_pageScale(0)
+    , m_frameHost(frameHost)
+    , m_originalThreadedScrollingEnabled(frameHost->settings().threadedScrollingEnabled())
+    , m_originalPageScaleConstraints(frameHost->pageScaleConstraintsSet().userAgentConstraints())
+{
+    // Force main thread scrolling, because we do not apply scroll position
+    // overrides in the compositor thread.
+    // TODO(eseckler): This does not prevent scroll position changes in the
+    // context of pinch gestures on the compositor thread (crbug.com/626277).
+    setThreadedScrollingEnabled(false);
+}
+
+void ScrollAndScaleEmulator::setThreadedScrollingEnabled(bool enabled)
+{
+    m_frameHost->settings().setThreadedScrollingEnabled(enabled);
+
+    // Ensure that the setting is propagated through ScrollingCoordinator::mainThreadScrollingReasons().
+    m_frameHost->page().scrollingCoordinator()->notifyGeometryChanged();
+
+    FrameView* view = m_frameHost->page().deprecatedLocalMainFrame()->view();
+    if (PaintLayerCompositor* compositor =
+        (view && !view->layoutViewItem().isNull())
+            ? view->layoutViewItem().compositor()
+            : nullptr)
+        compositor->setNeedsCompositingUpdate(CompositingUpdateAfterCompositingInputChange);
+}
+
+PageScaleConstraints ScrollAndScaleEmulator::pageScaleConstraints()
+{
+    if (m_pageScale > 0)
+        return PageScaleConstraints(m_pageScale, m_pageScale, m_pageScale);
+    return m_originalPageScaleConstraints;
+}
+
+template <typename Point>
+Point ScrollAndScaleEmulator::applyPositionOverride(const Point& position, const Point& override)
+{
+    Point newPosition = position;
+    if (override.x() >= 0)
+        newPosition.setX(override.x());
+    if (override.y() >= 0)
+        newPosition.setY(override.y());
+    return newPosition;
+}
+
+} // namespace blink