1 files changed, 59 insertions, 0 deletions
diff --git a/gfx/layers/apz/src/DragTracker.cpp b/gfx/layers/apz/src/DragTracker.cpp
new file mode 100644
index 0000000000..aa3b2a34f7
--- /dev/null
+++ b/gfx/layers/apz/src/DragTracker.cpp
@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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"
+#include "mozilla/Logging.h"
+
+static mozilla::LazyLogModule sApzDrgLog("apz.drag");
+#define DRAG_LOG(...) MOZ_LOG(sApzDrgLog, LogLevel::Debug, (__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