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..118d18ce74501b5513284e30c37205c63f7723c0
--- /dev/null
+++ b/third_party/WebKit/Source/core/frame/ScrollAndScaleEmulator.cpp
@@ -0,0 +1,123 @@
+/*
+ * 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/PageScaleConstraints.h"
+#include "core/frame/Settings.h"
+#include "core/page/Page.h"
+#include "core/page/scrolling/ScrollingCoordinator.h"
+#include "platform/geometry/DoublePoint.h"
+#include "public/platform/WebFloatPoint.h"
+#include "public/platform/WebPoint.h"
+#include "wtf/PassRefPtr.h"
+
+namespace blink {
+
+// static
+PassRefPtr<ScrollAndScaleEmulator> ScrollAndScaleEmulator::create()
+{
+    return adoptRef(new ScrollAndScaleEmulator);
+}
+
+bool ScrollAndScaleEmulator::update(const IntPoint& framePosition, const DoublePoint& visualViewportPosition, float pageScale)
+{
+    bool changed = false;
+
+    if (m_framePosition != framePosition) {
+        m_framePosition = framePosition;
+        changed |= true;

[bokan, 2016/07/01 21:05:12]

These can all just be `changed = true`

[Eric Seckler, 2016/07/04 14:33:08]

Done.

+    }
+
+    if (m_visualViewportPosition != visualViewportPosition) {
+        m_visualViewportPosition = visualViewportPosition;
+        changed |= true;
+    }
+
+    if (m_pageScale != pageScale) {
+        m_pageScale = pageScale;
+        changed |= true;
+    }
+
+    return changed;
+}
+
+IntPoint ScrollAndScaleEmulator::applyFramePositionOverride(const IntPoint& position, const IntPoint& minimum, const IntPoint& maximum)
+{
+    return applyPositionOverride(position, minimum, maximum, m_framePosition);
+}
+
+DoublePoint ScrollAndScaleEmulator::applyVisualViewportPositionOverride(const DoublePoint& position, const DoublePoint& minimum, const DoublePoint& maximum)
+{
+    return applyPositionOverride(position, minimum, maximum, m_visualViewportPosition);
+}
+
+PageScaleConstraints ScrollAndScaleEmulator::pageScaleConstraints()
+{
+    if (m_pageScale > 0)
+        return PageScaleConstraints(m_pageScale, m_pageScale, m_pageScale);
+    return PageScaleConstraints();
+}
+
+void ScrollAndScaleEmulator::disableThreadedScrolling(Page* page)
+{
+    m_threadedScrollingEnabledByDefault = (page->settings().threadedScrollingEnabled());

[bokan, 2016/07/01 21:05:12]

nit: no need for wrapping parenthesis here

[Eric Seckler, 2016/07/04 14:33:08]

Done.

+    page->settings().setThreadedScrollingEnabled(false);
+
+    // Ensure that the setting is propagated through ScrollingCoordinator::mainThreadScrollingReasons().
+    page->scrollingCoordinator()->notifyGeometryChanged();

[bokan, 2016/07/01 21:05:12]

I suspect you'll also need to call setNeedsCompositingUpdate on the root element
but I'm not very familiar here. We should loop in someone who knows. +vollick@

[Eric Seckler, 2016/07/04 14:33:08]

I think you're right. We need to make sure that
ScrollingCoordinator::updateAfterCompositingChangeIfNeeded() is called
eventually. I've added a
setNeedsCompositingUpdate(CompositingUpdateAfterGeometryChange) call to the
layoutView's compositor. vollick@, please let me know if this is the right way
to enforce this :)

[Ian Vollick, 2016/07/04 14:48:13]

Whether or not scrolling is updated is, I believe, a compositing input. I'd
think you want CompositingUpdateAfterCompositingInputChange in case compositing
gets enabled/disabled due to changing this setting.

[Eric Seckler, 2016/07/04 15:06:12]

Sounds good, changed to ..InputChange. Thanks, Ian!

+}
+
+void ScrollAndScaleEmulator::restoreThreadedScrolling(Page* page)
+{
+    page->settings().setThreadedScrollingEnabled(m_threadedScrollingEnabledByDefault);
+
+    // Ensure that the setting is propagated through ScrollingCoordinator::mainThreadScrollingReasons().
+    page->scrollingCoordinator()->notifyGeometryChanged();
+}
+
+ScrollAndScaleEmulator::ScrollAndScaleEmulator()
+    : m_pageScale(0)
+    , m_threadedScrollingEnabledByDefault(true)
+{
+}
+
+template <typename Point>
+Point ScrollAndScaleEmulator::applyPositionOverride(const Point& position, const Point& minimum, const Point& maximum, const Point& override)
+{
+    Point newPosition = position;
+    if (override.x() >= 0)
+        newPosition.setX(override.x());
+    if (override.y() >= 0)
+        newPosition.setY(override.y());
+    return newPosition.expandedTo(minimum).shrunkTo(maximum);
+}
+
+} // namespace blink