1 files changed, 175 insertions, 0 deletions
diff --git a/gfx/layers/apz/src/OverscrollHandoffState.cpp b/gfx/layers/apz/src/OverscrollHandoffState.cpp
new file mode 100644
index 000000000..577303fdd
--- /dev/null
+++ b/gfx/layers/apz/src/OverscrollHandoffState.cpp
@@ -0,0 +1,175 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et 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 "OverscrollHandoffState.h"
+
+#include <algorithm>              // for std::stable_sort
+#include "mozilla/Assertions.h"
+#include "AsyncPanZoomController.h"
+
+namespace mozilla {
+namespace layers {
+
+OverscrollHandoffChain::~OverscrollHandoffChain() {}
+
+void
+OverscrollHandoffChain::Add(AsyncPanZoomController* aApzc)
+{
+  mChain.push_back(aApzc);
+}
+
+struct CompareByScrollPriority
+{
+  bool operator()(const RefPtr<AsyncPanZoomController>& a,
+                  const RefPtr<AsyncPanZoomController>& b) const
+  {
+    return a->HasScrollgrab() && !b->HasScrollgrab();
+  }
+};
+
+void
+OverscrollHandoffChain::SortByScrollPriority()
+{
+  // The sorting being stable ensures that the relative order between
+  // non-scrollgrabbing APZCs remains child -> parent.
+  // (The relative order between scrollgrabbing APZCs will also remain
+  // child -> parent, though that's just an artefact of the implementation
+  // and users of 'scrollgrab' should not rely on this.)
+  std::stable_sort(mChain.begin(), mChain.end(), CompareByScrollPriority());
+}
+
+const RefPtr<AsyncPanZoomController>&
+OverscrollHandoffChain::GetApzcAtIndex(uint32_t aIndex) const
+{
+  MOZ_ASSERT(aIndex < Length());
+  return mChain[aIndex];
+}
+
+uint32_t
+OverscrollHandoffChain::IndexOf(const AsyncPanZoomController* aApzc) const
+{
+  uint32_t i;
+  for (i = 0; i < Length(); ++i) {
+    if (mChain[i] == aApzc) {
+      break;
+    }
+  }
+  return i;
+}
+
+void
+OverscrollHandoffChain::ForEachApzc(APZCMethod aMethod) const
+{
+  for (uint32_t i = 0; i < Length(); ++i) {
+    (mChain[i]->*aMethod)();
+  }
+}
+
+bool
+OverscrollHandoffChain::AnyApzc(APZCPredicate aPredicate) const
+{
+  MOZ_ASSERT(Length() > 0);
+  for (uint32_t i = 0; i < Length(); ++i) {
+    if ((mChain[i]->*aPredicate)()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void
+OverscrollHandoffChain::FlushRepaints() const
+{
+  ForEachApzc(&AsyncPanZoomController::FlushRepaintForOverscrollHandoff);
+}
+
+void
+OverscrollHandoffChain::CancelAnimations(CancelAnimationFlags aFlags) const
+{
+  MOZ_ASSERT(Length() > 0);
+  for (uint32_t i = 0; i < Length(); ++i) {
+    mChain[i]->CancelAnimation(aFlags);
+  }
+}
+
+void
+OverscrollHandoffChain::ClearOverscroll() const
+{
+  ForEachApzc(&AsyncPanZoomController::ClearOverscroll);
+}
+
+void
+OverscrollHandoffChain::SnapBackOverscrolledApzc(const AsyncPanZoomController* aStart) const
+{
+  uint32_t i = IndexOf(aStart);
+  for (; i < Length(); ++i) {
+    AsyncPanZoomController* apzc = mChain[i];
+    if (!apzc->IsDestroyed()) {
+      apzc->SnapBackIfOverscrolled();
+    }
+  }
+}
+
+bool
+OverscrollHandoffChain::CanBePanned(const AsyncPanZoomController* aApzc) const
+{
+  // Find |aApzc| in the handoff chain.
+  uint32_t i = IndexOf(aApzc);
+
+  // See whether any APZC in the handoff chain starting from |aApzc|
+  // has room to be panned.
+  for (uint32_t j = i; j < Length(); ++j) {
+    if (mChain[j]->IsPannable()) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool
+OverscrollHandoffChain::CanScrollInDirection(const AsyncPanZoomController* aApzc,
+                                             Layer::ScrollDirection aDirection) const
+{
+  // Find |aApzc| in the handoff chain.
+  uint32_t i = IndexOf(aApzc);
+
+  // See whether any APZC in the handoff chain starting from |aApzc|
+  // has room to scroll in the given direction.
+  for (uint32_t j = i; j < Length(); ++j) {
+    if (mChain[j]->CanScroll(aDirection)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool
+OverscrollHandoffChain::HasOverscrolledApzc() const
+{
+  return AnyApzc(&AsyncPanZoomController::IsOverscrolled);
+}
+
+bool
+OverscrollHandoffChain::HasFastFlungApzc() const
+{
+  return AnyApzc(&AsyncPanZoomController::IsFlingingFast);
+}
+
+RefPtr<AsyncPanZoomController>
+OverscrollHandoffChain::FindFirstScrollable(const InputData& aInput) const
+{
+  for (size_t i = 0; i < Length(); i++) {
+    if (mChain[i]->CanScroll(aInput)) {
+      return mChain[i];
+    }
+  }
+  return nullptr;
+}
+
+} // namespace layers
+} // namespace mozilla