Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.cpp

Index: third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.cpp
diff --git a/third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.cpp b/third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..9379854862d7b2f04595b43894c08d9115158bd7
--- /dev/null
+++ b/third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.cpp
@@ -0,0 +1,196 @@
+/*
+ * Copyright (C) 2016 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#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 {
+
+namespace {
+
+FrameView* frameViewFromPage(Page* page)
+{
+    if (!page->mainFrame() || !page->mainFrame()->isLocalFrame())

[bokan, 2016/07/04 22:44:09]

It might be more clear to make sure that we never create a
ScrollAndScaleEmulator from a remote iframe and simply ASSERT that the main
frame is local in the create method.

[Eric Seckler, 2016/07/05 16:46:51]

Done.

+        return nullptr;
+    return page->deprecatedLocalMainFrame()->view();
+}
+
+} // namespace
+
+// static
+PassRefPtr<ScrollAndScaleEmulator> ScrollAndScaleEmulator::create(Page* page)
+{
+    ScrollAndScaleEmulator* emulator = new ScrollAndScaleEmulator();
+
+    // Force main thread scrolling, because we do not apply scroll position
+    // overrides in the compositor thread.
+    emulator->disableThreadedScrolling(page);

[bokan, 2016/07/04 22:44:09]

Similarly to the UA constraints, store m_originalThreadedScrollingEnabled from
this method as well. As it is, calling disableThreadedScrolling twice would
overwrite that.

[Eric Seckler, 2016/07/05 16:46:51]

Done.

+
+    emulator->setOriginalPageScaleConstraints(
+        page->frameHost().pageScaleConstraintsSet().userAgentConstraints());
+
+    return adoptRef(emulator);
+}
+
+void ScrollAndScaleEmulator::update(Page* page, 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 = frameViewFromPage(page))
+            view->setScrollAndScaleEmulator(this);
+        page->frameHost().setUserAgentPageScaleConstraints(pageScaleConstraints());
+        page->frameHost().visualViewport().setScrollAndScaleEmulator(this);
+    }
+}
+
+void ScrollAndScaleEmulator::clear(Page* page)
+{
+    m_framePosition = IntPoint(-1, -1);
+    m_visualViewportPosition = DoublePoint(-1, -1);
+    m_pageScale = 0;
+
+    restoreThreadedScrolling(page);
+
+    if (FrameView* view = frameViewFromPage(page))
+        view->setScrollAndScaleEmulator(nullptr);
+    page->frameHost().setUserAgentPageScaleConstraints(m_originalPageScaleConstraints);
+    page->frameHost().visualViewport().setScrollAndScaleEmulator(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(Page* page, const IntSize& webViewSize)
+{
+    PageScaleConstraintsSet constraints = page->frameHost().pageScaleConstraintsSet();
+    constraints.setUserAgentConstraints(m_originalPageScaleConstraints);

[bokan, 2016/07/04 22:44:09]

Add a short comment as to why this is necessary.

[Eric Seckler, 2016/07/05 16:46:51]

Done.

+    constraints.computeFinalConstraints();
+
+    FloatSize frameSize(webViewSize);
+    frameSize.scale(1 / constraints.finalConstraints().minimumScale);
+    return expandedIntSize(frameSize);
+}
+
+ScrollAndScaleEmulator::ScrollAndScaleEmulator()
+    : m_framePosition(IntPoint(-1, -1))
+    , m_visualViewportPosition(DoublePoint(-1, -1))
+    , m_pageScale(0)
+    , m_originalThreadedScrollingEnabled(true)
+{
+}
+
+void ScrollAndScaleEmulator::disableThreadedScrolling(Page* page)
+{
+    m_originalThreadedScrollingEnabled = page->settings().threadedScrollingEnabled();
+    page->settings().setThreadedScrollingEnabled(false);
+
+    // Ensure that the setting is propagated through ScrollingCoordinator::mainThreadScrollingReasons().
+    page->scrollingCoordinator()->notifyGeometryChanged();

[bokan, 2016/07/04 22:44:09]

Factor the notifyGeometryChanged and needsCompositingUpdate calls into a helper.

[Eric Seckler, 2016/07/05 16:46:51]

Done.

+
+    FrameView* view = frameViewFromPage(page);
+    if (PaintLayerCompositor* compositor =
+        (view && !view->layoutViewItem().isNull())
+            ? view->layoutViewItem().compositor()
+            : nullptr)
+        compositor->setNeedsCompositingUpdate(CompositingUpdateAfterCompositingInputChange);
+}
+
+void ScrollAndScaleEmulator::restoreThreadedScrolling(Page* page)
+{
+    page->settings().setThreadedScrollingEnabled(m_originalThreadedScrollingEnabled);
+
+    // Ensure that the setting is propagated through ScrollingCoordinator::mainThreadScrollingReasons().
+    page->scrollingCoordinator()->notifyGeometryChanged();
+
+    FrameView* view = frameViewFromPage(page);
+    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;
+}
+
+void ScrollAndScaleEmulator::setOriginalPageScaleConstraints(const PageScaleConstraints& constraints)
+{
+    m_originalPageScaleConstraints = constraints;
+}
+
+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