1 files changed, 237 insertions, 0 deletions
diff --git a/gfx/layers/apz/src/FocusState.cpp b/gfx/layers/apz/src/FocusState.cpp
new file mode 100644
index 0000000000..0230676e7e
--- /dev/null
+++ b/gfx/layers/apz/src/FocusState.cpp
@@ -0,0 +1,237 @@
+/* -*- 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 "FocusState.h"
+
+#include "mozilla/Logging.h"
+#include "mozilla/layers/APZThreadUtils.h"
+
+static mozilla::LazyLogModule sApzFstLog("apz.focusstate");
+#define FS_LOG(...) MOZ_LOG(sApzFstLog, LogLevel::Debug, (__VA_ARGS__))
+
+namespace mozilla {
+namespace layers {
+
+FocusState::FocusState()
+    : mMutex("FocusStateMutex"),
+      mLastAPZProcessedEvent(1),
+      mLastContentProcessedEvent(0),
+      mFocusHasKeyEventListeners(false),
+      mReceivedUpdate(false),
+      mFocusLayersId{0},
+      mFocusHorizontalTarget(ScrollableLayerGuid::NULL_SCROLL_ID),
+      mFocusVerticalTarget(ScrollableLayerGuid::NULL_SCROLL_ID) {}
+
+uint64_t FocusState::LastAPZProcessedEvent() const {
+  APZThreadUtils::AssertOnControllerThread();
+  MutexAutoLock lock(mMutex);
+
+  return mLastAPZProcessedEvent;
+}
+
+bool FocusState::IsCurrent(const MutexAutoLock& aProofOfLock) const {
+  FS_LOG("Checking IsCurrent() with cseq=%" PRIu64 ", aseq=%" PRIu64 "\n",
+         mLastContentProcessedEvent, mLastAPZProcessedEvent);
+  MOZ_ASSERT(mLastContentProcessedEvent <= mLastAPZProcessedEvent);
+  return mLastContentProcessedEvent == mLastAPZProcessedEvent;
+}
+
+void FocusState::ReceiveFocusChangingEvent() {
+  APZThreadUtils::AssertOnControllerThread();
+  MutexAutoLock lock(mMutex);
+
+  if (!mReceivedUpdate) {
+    // In the initial state don't advance mLastAPZProcessedEvent because we
+    // might blow away the information that we're in a freshly-restarted GPU
+    // process. This information (i.e. that mLastAPZProcessedEvent == 1) needs
+    // to be preserved until the first call to Update() which will then advance
+    // mLastAPZProcessedEvent to match the content-side sequence number.
+    return;
+  }
+  mLastAPZProcessedEvent += 1;
+  FS_LOG("Focus changing event incremented aseq to %" PRIu64 ", (%p)\n",
+         mLastAPZProcessedEvent, this);
+}
+
+void FocusState::Update(LayersId aRootLayerTreeId,
+                        LayersId aOriginatingLayersId,
+                        const FocusTarget& aState) {
+  // This runs on the updater thread, it's not worth passing around extra raw
+  // pointers just to assert it.
+
+  MutexAutoLock lock(mMutex);
+
+  FS_LOG("Update with rlt=%" PRIu64 ", olt=%" PRIu64 ", ft=(%s, %" PRIu64 ")\n",
+         aRootLayerTreeId.mId, aOriginatingLayersId.mId, aState.Type(),
+         aState.mSequenceNumber);
+  mReceivedUpdate = true;
+
+  // Update the focus tree with the latest target
+  mFocusTree[aOriginatingLayersId] = aState;
+
+  // Reset our internal state so we can recalculate it
+  mFocusHasKeyEventListeners = false;
+  mFocusLayersId = aRootLayerTreeId;
+  mFocusHorizontalTarget = ScrollableLayerGuid::NULL_SCROLL_ID;
+  mFocusVerticalTarget = ScrollableLayerGuid::NULL_SCROLL_ID;
+
+  // To update the focus state for the entire APZCTreeManager, we need
+  // to traverse the focus tree to find the current leaf which is the global
+  // focus target we can use for async keyboard scrolling
+  while (true) {
+    auto currentNode = mFocusTree.find(mFocusLayersId);
+    if (currentNode == mFocusTree.end()) {
+      FS_LOG("Setting target to nil (cannot find lt=%" PRIu64 ")\n",
+             mFocusLayersId.mId);
+      return;
+    }
+
+    const FocusTarget& target = currentNode->second;
+
+    // Accumulate event listener flags on the path to the focus target
+    mFocusHasKeyEventListeners |= target.mFocusHasKeyEventListeners;
+
+    // Match on the data stored in mData
+    // The match functions return true or false depending on whether the
+    // enclosing method, FocusState::Update, should return or continue to the
+    // next iteration of the while loop, respectively.
+    struct FocusTargetDataMatcher {
+      FocusState& mFocusState;
+      const uint64_t mSequenceNumber;
+
+      bool operator()(const FocusTarget::NoFocusTarget& aNoFocusTarget) {
+        FS_LOG("Setting target to nil (reached a nil target) with seq=%" PRIu64
+               ", (%p)\n",
+               mSequenceNumber, &mFocusState);
+
+        // Mark what sequence number this target has for debugging purposes so
+        // we can always accurately report on whether we are stale or not
+        mFocusState.mLastContentProcessedEvent = mSequenceNumber;
+
+        // If this focus state was just created and content has experienced more
+        // events then us, then assume we were recreated and sync focus sequence
+        // numbers.
+        if (mFocusState.mLastAPZProcessedEvent == 1 &&
+            mFocusState.mLastContentProcessedEvent >
+                mFocusState.mLastAPZProcessedEvent) {
+          mFocusState.mLastAPZProcessedEvent =
+              mFocusState.mLastContentProcessedEvent;
+        }
+        return true;
+      }
+
+      bool operator()(const LayersId& aRefLayerId) {
+        // Guard against infinite loops
+        MOZ_ASSERT(mFocusState.mFocusLayersId != aRefLayerId);
+        if (mFocusState.mFocusLayersId == aRefLayerId) {
+          FS_LOG(
+              "Setting target to nil (bailing out of infinite loop, lt=%" PRIu64
+              ")\n",
+              mFocusState.mFocusLayersId.mId);
+          return true;
+        }
+
+        FS_LOG("Looking for target in lt=%" PRIu64 "\n", aRefLayerId.mId);
+
+        // The focus target is in a child layer tree
+        mFocusState.mFocusLayersId = aRefLayerId;
+        return false;
+      }
+
+      bool operator()(const FocusTarget::ScrollTargets& aScrollTargets) {
+        FS_LOG("Setting target to h=%" PRIu64 ", v=%" PRIu64
+               ", and seq=%" PRIu64 "(%p)\n",
+               aScrollTargets.mHorizontal, aScrollTargets.mVertical,
+               mSequenceNumber, &mFocusState);
+
+        // This is the global focus target
+        mFocusState.mFocusHorizontalTarget = aScrollTargets.mHorizontal;
+        mFocusState.mFocusVerticalTarget = aScrollTargets.mVertical;
+
+        // Mark what sequence number this target has so we can determine whether
+        // it is stale or not
+        mFocusState.mLastContentProcessedEvent = mSequenceNumber;
+
+        // If this focus state was just created and content has experienced more
+        // events then us, then assume we were recreated and sync focus sequence
+        // numbers.
+        if (mFocusState.mLastAPZProcessedEvent == 1 &&
+            mFocusState.mLastContentProcessedEvent >
+                mFocusState.mLastAPZProcessedEvent) {
+          mFocusState.mLastAPZProcessedEvent =
+              mFocusState.mLastContentProcessedEvent;
+        }
+        return true;
+      }
+    };  // struct FocusTargetDataMatcher
+
+    if (target.mData.match(
+            FocusTargetDataMatcher{*this, target.mSequenceNumber})) {
+      return;
+    }
+  }
+}
+
+void FocusState::RemoveFocusTarget(LayersId aLayersId) {
+  // This runs on the updater thread, it's not worth passing around extra raw
+  // pointers just to assert it.
+  MutexAutoLock lock(mMutex);
+
+  mFocusTree.erase(aLayersId);
+}
+
+Maybe<ScrollableLayerGuid> FocusState::GetHorizontalTarget() const {
+  APZThreadUtils::AssertOnControllerThread();
+  MutexAutoLock lock(mMutex);
+
+  // There is not a scrollable layer to async scroll if
+  //   1. We aren't current
+  //   2. There are event listeners that could change the focus
+  //   3. The target has not been layerized
+  if (!IsCurrent(lock) || mFocusHasKeyEventListeners ||
+      mFocusHorizontalTarget == ScrollableLayerGuid::NULL_SCROLL_ID) {
+    return Nothing();
+  }
+  return Some(ScrollableLayerGuid(mFocusLayersId, 0, mFocusHorizontalTarget));
+}
+
+Maybe<ScrollableLayerGuid> FocusState::GetVerticalTarget() const {
+  APZThreadUtils::AssertOnControllerThread();
+  MutexAutoLock lock(mMutex);
+
+  // There is not a scrollable layer to async scroll if:
+  //   1. We aren't current
+  //   2. There are event listeners that could change the focus
+  //   3. The target has not been layerized
+  if (!IsCurrent(lock) || mFocusHasKeyEventListeners ||
+      mFocusVerticalTarget == ScrollableLayerGuid::NULL_SCROLL_ID) {
+    return Nothing();
+  }
+  return Some(ScrollableLayerGuid(mFocusLayersId, 0, mFocusVerticalTarget));
+}
+
+bool FocusState::CanIgnoreKeyboardShortcutMisses() const {
+  APZThreadUtils::AssertOnControllerThread();
+  MutexAutoLock lock(mMutex);
+
+  return IsCurrent(lock) && !mFocusHasKeyEventListeners;
+}
+
+void FocusState::Reset() {
+  MutexAutoLock lock(mMutex);
+
+  mLastAPZProcessedEvent = 1;
+  mLastContentProcessedEvent = 0;
+  mFocusHasKeyEventListeners = false;
+  mReceivedUpdate = false;
+  mFocusLayersId = {0};
+  mFocusHorizontalTarget = ScrollableLayerGuid::NULL_SCROLL_ID;
+  mFocusVerticalTarget = ScrollableLayerGuid::NULL_SCROLL_ID;
+  mFocusTree = {};
+}
+
+}  // namespace layers
+}  // namespace mozilla