1 files changed, 74 insertions, 0 deletions
diff --git a/gfx/layers/apz/util/TouchCounter.cpp b/gfx/layers/apz/util/TouchCounter.cpp
new file mode 100644
index 0000000000..9e4d6f1ba6
--- /dev/null
+++ b/gfx/layers/apz/util/TouchCounter.cpp
@@ -0,0 +1,74 @@
+/* -*- 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 "TouchCounter.h"
+
+#include "InputData.h"
+#include "mozilla/TouchEvents.h"
+
+namespace mozilla {
+namespace layers {
+
+TouchCounter::TouchCounter() : mActiveTouchCount(0) {}
+
+void TouchCounter::Update(const MultiTouchInput& aInput) {
+  switch (aInput.mType) {
+    case MultiTouchInput::MULTITOUCH_START:
+      // touch-start event contains all active touches of the current session
+      mActiveTouchCount = aInput.mTouches.Length();
+      break;
+    case MultiTouchInput::MULTITOUCH_END:
+      if (mActiveTouchCount >= aInput.mTouches.Length()) {
+        // touch-end event contains only released touches
+        mActiveTouchCount -= aInput.mTouches.Length();
+      } else {
+        NS_WARNING("Got an unexpected touchend");
+        mActiveTouchCount = 0;
+      }
+      break;
+    case MultiTouchInput::MULTITOUCH_CANCEL:
+      mActiveTouchCount = 0;
+      break;
+    case MultiTouchInput::MULTITOUCH_MOVE:
+      break;
+  }
+}
+
+void TouchCounter::Update(const WidgetTouchEvent& aEvent) {
+  switch (aEvent.mMessage) {
+    case eTouchStart:
+      // touch-start event contains all active touches of the current session
+      mActiveTouchCount = aEvent.mTouches.Length();
+      break;
+    case eTouchEnd: {
+      // touch-end contains all touches, but ones being lifted are marked as
+      // changed
+      uint32_t liftedTouches = 0;
+      for (const auto& touch : aEvent.mTouches) {
+        if (touch->mChanged) {
+          liftedTouches++;
+        }
+      }
+      if (mActiveTouchCount >= liftedTouches) {
+        mActiveTouchCount -= liftedTouches;
+      } else {
+        NS_WARNING("Got an unexpected touchend");
+        mActiveTouchCount = 0;
+      }
+      break;
+    }
+    case eTouchCancel:
+      mActiveTouchCount = 0;
+      break;
+    default:
+      break;
+  }
+}
+
+uint32_t TouchCounter::GetActiveTouchCount() const { return mActiveTouchCount; }
+
+}  // namespace layers
+}  // namespace mozilla