Adds scroll position/scale emulation to DevTools.

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

+// 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.
+
+#ifndef ScrollAndScaleEmulator_h
+#define ScrollAndScaleEmulator_h
+
+#include "core/CoreExport.h"
+#include "core/frame/PageScaleConstraints.h"
+#include "platform/geometry/DoublePoint.h"
+#include "platform/geometry/IntPoint.h"
+#include "platform/heap/Handle.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/PassRefPtr.h"
+#include "wtf/RefCounted.h"
+
+namespace blink {
+
+class FrameHost;
+class IntSize;
+
+// Overrides the scroll positions of frame and visual viewport and the page
+// scale with fixed values.
+//
+// Scroll position overrides are enforced within VisualViewport and FrameView
+// by manipulating their minimum/maximum scroll positions. The override is then
+// applied when the scroll position is clamped to these min/max values.
+//
+// Similarly, the scale override is enforced through setting custom user-agent
+// PageScaleConstraints in WebViewImpl.
+class CORE_EXPORT ScrollAndScaleEmulator final : public GarbageCollected<ScrollAndScaleEmulator> {
+    WTF_MAKE_NONCOPYABLE(ScrollAndScaleEmulator);
+public:
+    // Create a new emulator instance. Also disables threaded scrolling for the
+    // frame's page while the override is in effect.
+    static ScrollAndScaleEmulator* create(FrameHost*);
+
+    DECLARE_TRACE();
+
+    // Enforce new override values, notify viewports about changes.
+    void update(const IntPoint& framePosition, const DoublePoint& visualViewportPosition, float pageScale);
+
+    // Clear overrides, notify viewports about changes. Also restores threaded
+    // scrolling settings and original user-agent PageScaleConstraints.
+    void clear();
+
+    // Return main frame scroll position with active overrides for individual
+    // coordinates applied.
+    IntPoint applyFramePositionOverride(const IntPoint&);
+
+    // Return visual viewport scroll position with active overrides for
+    // individual coordinates applied.
+    DoublePoint applyVisualViewportPositionOverride(const DoublePoint&);
+
+    // Calculate and return main frame size for original PageScaleConstraints.
+    IntSize mainFrameSize(const IntSize& webViewSize);
+
+private:
+    ScrollAndScaleEmulator(FrameHost*);
+
+    // Return PageScaleConstraints that enforce any active page scale override.
+    // Defaults to original constraints if no override is active.
+    PageScaleConstraints pageScaleConstraints();
+
+    void setThreadedScrollingEnabled(bool);
+
+    template <typename Point>
+    Point applyPositionOverride(const Point& position, const Point& override);
+
+    // Scroll position of frame. |x < 0| or |y < 0| disables the override for the respective coordinate.
+    IntPoint m_framePosition;
+
+    // Scroll position of visual viewport. |x < 0| or |y < 0| disables the override for the respective coordinate.
+    DoublePoint m_visualViewportPosition;
+
+    // Simulates visual viewport pinch zoom. |pageScale == 0| disables the override.
+    double m_pageScale;
+
+    Member<FrameHost> m_frameHost;
+
+    bool m_originalThreadedScrollingEnabled;
+    PageScaleConstraints m_originalPageScaleConstraints;
+};
+
+} // namespace blink
+
+#endif // ScrollAndScaleEmulator_h