1 files changed, 70 insertions, 0 deletions
diff --git a/gfx/layers/apz/src/DragTracker.cpp b/gfx/layers/apz/src/DragTracker.cpp
new file mode 100644
index 000000000..ecd3ff16f
--- /dev/null
+++ b/gfx/layers/apz/src/DragTracker.cpp
@@ -0,0 +1,70 @@
+/* -*- 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/. */
+
+#include "DragTracker.h"
+
+#include "InputData.h"
+
+#define DRAG_LOG(...)
+// #define DRAG_LOG(...) printf_stderr("DRAG: " __VA_ARGS__)
+
+namespace mozilla {
+namespace layers {
+
+DragTracker::DragTracker()
+  : mInDrag(false)
+{
+}
+
+/*static*/ bool
+DragTracker::StartsDrag(const MouseInput& aInput)
+{
+  return aInput.IsLeftButton() && aInput.mType == MouseInput::MOUSE_DOWN;
+}
+
+/*static*/ bool
+DragTracker::EndsDrag(const MouseInput& aInput)
+{
+  // On Windows, we don't receive a MOUSE_UP at the end of a drag if an
+  // actual drag session took place. As a backup, we detect the end of the
+  // drag using the MOUSE_DRAG_END event, which normally is routed directly
+  // to content, but we're specially routing to APZ for this purpose. Bug
+  // 1265105 tracks a solution to this at the Windows widget layer; once
+  // that is implemented, this workaround can be removed.
+  return (aInput.IsLeftButton() && aInput.mType == MouseInput::MOUSE_UP)
+      || aInput.mType == MouseInput::MOUSE_DRAG_END;
+}
+
+void
+DragTracker::Update(const MouseInput& aInput)
+{
+  if (StartsDrag(aInput)) {
+    DRAG_LOG("Starting drag\n");
+    mInDrag = true;
+  } else if (EndsDrag(aInput)) {
+    DRAG_LOG("Ending drag\n");
+    mInDrag = false;
+    mOnScrollbar = Nothing();
+  }
+}
+
+bool
+DragTracker::InDrag() const
+{
+  return mInDrag;
+}
+
+bool
+DragTracker::IsOnScrollbar(bool aOnScrollbar)
+{
+  if (!mOnScrollbar) {
+    DRAG_LOG("Setting hitscrollbar %d\n", aOnScrollbar);
+    mOnScrollbar = Some(aOnScrollbar);
+  }
+  return mOnScrollbar.value();
+}
+
+} // namespace layers
+} // namespace mozilla