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-rw-r--r--gfx/layers/apz/src/DragTracker.h39
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diff --git a/gfx/layers/apz/src/DragTracker.h b/gfx/layers/apz/src/DragTracker.h
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+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_DragTracker_h
+#define mozilla_layers_DragTracker_h
+
+#include "mozilla/EventForwards.h"
+#include "mozilla/Maybe.h"
+
+namespace mozilla {
+
+class MouseInput;
+
+namespace layers {
+
+// DragTracker simply tracks a sequence of mouse inputs and allows us to tell
+// if we are in a drag or not (i.e. the left mouse button went down and hasn't
+// gone up yet).
+class DragTracker
+{
+public:
+ DragTracker();
+ static bool StartsDrag(const MouseInput& aInput);
+ static bool EndsDrag(const MouseInput& aInput);
+ void Update(const MouseInput& aInput);
+ bool InDrag() const;
+ bool IsOnScrollbar(bool aOnScrollbar);
+
+private:
+ Maybe<bool> mOnScrollbar;
+ bool mInDrag;
+};
+
+} // namespace layers
+} // namespace mozilla
+
+#endif /* mozilla_layers_DragTracker_h */