1 files changed, 546 insertions, 0 deletions
diff --git a/gfx/layers/apz/src/APZUpdater.cpp b/gfx/layers/apz/src/APZUpdater.cpp
new file mode 100644
index 0000000000..2bbad6e1a7
--- /dev/null
+++ b/gfx/layers/apz/src/APZUpdater.cpp
@@ -0,0 +1,546 @@
+/* -*- 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 "mozilla/layers/APZUpdater.h"
+
+#include "APZCTreeManager.h"
+#include "AsyncPanZoomController.h"
+#include "base/task.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/layers/APZThreadUtils.h"
+#include "mozilla/layers/CompositorThread.h"
+#include "mozilla/layers/SynchronousTask.h"
+#include "mozilla/layers/WebRenderScrollDataWrapper.h"
+#include "mozilla/webrender/WebRenderAPI.h"
+
+namespace mozilla {
+namespace layers {
+
+StaticMutex APZUpdater::sWindowIdLock;
+StaticAutoPtr<std::unordered_map<uint64_t, APZUpdater*>>
+    APZUpdater::sWindowIdMap;
+
+APZUpdater::APZUpdater(const RefPtr<APZCTreeManager>& aApz,
+                       bool aConnectedToWebRender)
+    : mApz(aApz),
+      mDestroyed(false),
+      mConnectedToWebRender(aConnectedToWebRender),
+      mThreadIdLock("APZUpdater::ThreadIdLock"),
+      mQueueLock("APZUpdater::QueueLock") {
+  MOZ_ASSERT(aApz);
+  mApz->SetUpdater(this);
+}
+
+APZUpdater::~APZUpdater() {
+  mApz->SetUpdater(nullptr);
+
+  StaticMutexAutoLock lock(sWindowIdLock);
+  if (mWindowId) {
+    MOZ_ASSERT(sWindowIdMap);
+    // Ensure that ClearTree was called and the task got run
+    MOZ_ASSERT(sWindowIdMap->find(wr::AsUint64(*mWindowId)) ==
+               sWindowIdMap->end());
+  }
+}
+
+bool APZUpdater::HasTreeManager(const RefPtr<APZCTreeManager>& aApz) {
+  return aApz.get() == mApz.get();
+}
+
+void APZUpdater::SetWebRenderWindowId(const wr::WindowId& aWindowId) {
+  StaticMutexAutoLock lock(sWindowIdLock);
+  MOZ_ASSERT(!mWindowId);
+  mWindowId = Some(aWindowId);
+  if (!sWindowIdMap) {
+    sWindowIdMap = new std::unordered_map<uint64_t, APZUpdater*>();
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "APZUpdater::ClearOnShutdown", [] { ClearOnShutdown(&sWindowIdMap); }));
+  }
+  (*sWindowIdMap)[wr::AsUint64(aWindowId)] = this;
+}
+
+/*static*/
+void APZUpdater::SetUpdaterThread(const wr::WrWindowId& aWindowId) {
+  if (RefPtr<APZUpdater> updater = GetUpdater(aWindowId)) {
+    MutexAutoLock lock(updater->mThreadIdLock);
+    updater->mUpdaterThreadId = Some(PlatformThread::CurrentId());
+  }
+}
+
+// Takes a conditional lock!
+/*static*/
+void APZUpdater::PrepareForSceneSwap(const wr::WrWindowId& aWindowId)
+    MOZ_NO_THREAD_SAFETY_ANALYSIS {
+  if (RefPtr<APZUpdater> updater = GetUpdater(aWindowId)) {
+    updater->mApz->LockTree();
+  }
+}
+
+// Assumes we took a conditional lock!
+/*static*/
+void APZUpdater::CompleteSceneSwap(const wr::WrWindowId& aWindowId,
+                                   const wr::WrPipelineInfo& aInfo) {
+  RefPtr<APZUpdater> updater = GetUpdater(aWindowId);
+  if (!updater) {
+    // This should only happen in cases where PrepareForSceneSwap also got a
+    // null updater. No updater-thread tasks get run between PrepareForSceneSwap
+    // and this function, so there is no opportunity for the updater mapping
+    // to have gotten removed from sWindowIdMap in between the two calls.
+    return;
+  }
+  updater->mApz->mTreeLock.AssertCurrentThreadIn();
+
+  for (const auto& removedPipeline : aInfo.removed_pipelines) {
+    LayersId layersId = wr::AsLayersId(removedPipeline.pipeline_id);
+    updater->mEpochData.erase(layersId);
+  }
+  // Reset the built info for all pipelines, then put it back for the ones
+  // that got built in this scene swap.
+  for (auto& i : updater->mEpochData) {
+    i.second.mBuilt = Nothing();
+  }
+  for (const auto& epoch : aInfo.epochs) {
+    LayersId layersId = wr::AsLayersId(epoch.pipeline_id);
+    updater->mEpochData[layersId].mBuilt = Some(epoch.epoch);
+  }
+
+  // Run any tasks that got unblocked, then unlock the tree. The order is
+  // important because we want to run all the tasks up to and including the
+  // UpdateHitTestingTree calls corresponding to the built epochs, and we
+  // want to run those before we release the lock (i.e. atomically with the
+  // scene swap). This ensures that any hit-tests always encounter a consistent
+  // state between the APZ tree and the built scene in WR.
+  //
+  // While we could add additional information to the queued tasks to figure
+  // out the minimal set of tasks we want to run here, it's easier and harmless
+  // to just run all the queued and now-unblocked tasks inside the lock.
+  //
+  // Note that the ProcessQueue here might remove the window id -> APZUpdater
+  // mapping from sWindowIdMap, but we still unlock the tree successfully to
+  // leave things in a good state.
+  updater->ProcessQueue();
+
+  updater->mApz->UnlockTree();
+}
+
+/*static*/
+void APZUpdater::ProcessPendingTasks(const wr::WrWindowId& aWindowId) {
+  if (RefPtr<APZUpdater> updater = GetUpdater(aWindowId)) {
+    updater->ProcessQueue();
+  }
+}
+
+void APZUpdater::ClearTree(LayersId aRootLayersId) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RefPtr<APZUpdater> self = this;
+  RunOnUpdaterThread(aRootLayersId,
+                     NS_NewRunnableFunction("APZUpdater::ClearTree", [=]() {
+                       self->mApz->ClearTree();
+                       self->mDestroyed = true;
+
+                       // Once ClearTree is called on the APZCTreeManager, we
+                       // are in a shutdown phase. After this point it's ok if
+                       // WebRender cannot get a hold of the updater via the
+                       // window id, and it's a good point to remove the mapping
+                       // and avoid leaving a dangling pointer to this object.
+                       StaticMutexAutoLock lock(sWindowIdLock);
+                       if (self->mWindowId) {
+                         MOZ_ASSERT(sWindowIdMap);
+                         sWindowIdMap->erase(wr::AsUint64(*(self->mWindowId)));
+                       }
+                     }));
+}
+
+void APZUpdater::UpdateFocusState(LayersId aRootLayerTreeId,
+                                  LayersId aOriginatingLayersId,
+                                  const FocusTarget& aFocusTarget) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RunOnUpdaterThread(aOriginatingLayersId,
+                     NewRunnableMethod<LayersId, LayersId, FocusTarget>(
+                         "APZUpdater::UpdateFocusState", mApz,
+                         &APZCTreeManager::UpdateFocusState, aRootLayerTreeId,
+                         aOriginatingLayersId, aFocusTarget));
+}
+
+void APZUpdater::UpdateScrollDataAndTreeState(
+    LayersId aRootLayerTreeId, LayersId aOriginatingLayersId,
+    const wr::Epoch& aEpoch, WebRenderScrollData&& aScrollData) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RefPtr<APZUpdater> self = this;
+  // Insert an epoch requirement update into the queue, so that
+  // tasks inserted into the queue after this point only get executed
+  // once the epoch requirement is satisfied. In particular, the
+  // UpdateHitTestingTree call below needs to wait until the epoch requirement
+  // is satisfied, which is why it is a separate task in the queue.
+  RunOnUpdaterThread(
+      aOriginatingLayersId,
+      NS_NewRunnableFunction("APZUpdater::UpdateEpochRequirement", [=]() {
+        if (aRootLayerTreeId == aOriginatingLayersId) {
+          self->mEpochData[aOriginatingLayersId].mIsRoot = true;
+        }
+        self->mEpochData[aOriginatingLayersId].mRequired = aEpoch;
+      }));
+  RunOnUpdaterThread(
+      aOriginatingLayersId,
+      NS_NewRunnableFunction(
+          "APZUpdater::UpdateHitTestingTree",
+          [=, aScrollData = std::move(aScrollData)]() mutable {
+            auto isFirstPaint = aScrollData.IsFirstPaint();
+            auto paintSequenceNumber = aScrollData.GetPaintSequenceNumber();
+
+            self->mScrollData[aOriginatingLayersId] = std::move(aScrollData);
+            auto root = self->mScrollData.find(aRootLayerTreeId);
+            if (root == self->mScrollData.end()) {
+              return;
+            }
+            self->mApz->UpdateHitTestingTree(
+                WebRenderScrollDataWrapper(*self, &(root->second)),
+                isFirstPaint, aOriginatingLayersId, paintSequenceNumber);
+          }));
+}
+
+void APZUpdater::UpdateScrollOffsets(LayersId aRootLayerTreeId,
+                                     LayersId aOriginatingLayersId,
+                                     ScrollUpdatesMap&& aUpdates,
+                                     uint32_t aPaintSequenceNumber) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RefPtr<APZUpdater> self = this;
+  RunOnUpdaterThread(
+      aOriginatingLayersId,
+      NS_NewRunnableFunction(
+          "APZUpdater::UpdateScrollOffsets",
+          [=, updates = std::move(aUpdates)]() mutable {
+            self->mScrollData[aOriginatingLayersId].ApplyUpdates(
+                std::move(updates), aPaintSequenceNumber);
+            auto root = self->mScrollData.find(aRootLayerTreeId);
+            if (root == self->mScrollData.end()) {
+              return;
+            }
+            self->mApz->UpdateHitTestingTree(
+                WebRenderScrollDataWrapper(*self, &(root->second)),
+                /*isFirstPaint*/ false, aOriginatingLayersId,
+                aPaintSequenceNumber);
+          }));
+}
+
+void APZUpdater::NotifyLayerTreeAdopted(LayersId aLayersId,
+                                        const RefPtr<APZUpdater>& aOldUpdater) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RunOnUpdaterThread(aLayersId,
+                     NewRunnableMethod<LayersId, RefPtr<APZCTreeManager>>(
+                         "APZUpdater::NotifyLayerTreeAdopted", mApz,
+                         &APZCTreeManager::NotifyLayerTreeAdopted, aLayersId,
+                         aOldUpdater ? aOldUpdater->mApz : nullptr));
+}
+
+void APZUpdater::NotifyLayerTreeRemoved(LayersId aLayersId) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RefPtr<APZUpdater> self = this;
+  RunOnUpdaterThread(
+      aLayersId,
+      NS_NewRunnableFunction("APZUpdater::NotifyLayerTreeRemoved", [=]() {
+        self->mEpochData.erase(aLayersId);
+        self->mScrollData.erase(aLayersId);
+        self->mApz->NotifyLayerTreeRemoved(aLayersId);
+      }));
+}
+
+bool APZUpdater::GetAPZTestData(LayersId aLayersId, APZTestData* aOutData) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+
+  RefPtr<APZCTreeManager> apz = mApz;
+  bool ret = false;
+  SynchronousTask waiter("APZUpdater::GetAPZTestData");
+  RunOnUpdaterThread(
+      aLayersId, NS_NewRunnableFunction("APZUpdater::GetAPZTestData", [&]() {
+        AutoCompleteTask notifier(&waiter);
+        ret = apz->GetAPZTestData(aLayersId, aOutData);
+      }));
+
+  // Wait until the task posted above has run and populated aOutData and ret
+  waiter.Wait();
+
+  return ret;
+}
+
+void APZUpdater::SetTestAsyncScrollOffset(
+    LayersId aLayersId, const ScrollableLayerGuid::ViewID& aScrollId,
+    const CSSPoint& aOffset) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RefPtr<APZCTreeManager> apz = mApz;
+  RunOnUpdaterThread(
+      aLayersId,
+      NS_NewRunnableFunction("APZUpdater::SetTestAsyncScrollOffset", [=]() {
+        RefPtr<AsyncPanZoomController> apzc =
+            apz->GetTargetAPZC(aLayersId, aScrollId);
+        if (apzc) {
+          apzc->SetTestAsyncScrollOffset(aOffset);
+        } else {
+          NS_WARNING("Unable to find APZC in SetTestAsyncScrollOffset");
+        }
+      }));
+}
+
+void APZUpdater::SetTestAsyncZoom(LayersId aLayersId,
+                                  const ScrollableLayerGuid::ViewID& aScrollId,
+                                  const LayerToParentLayerScale& aZoom) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+  RefPtr<APZCTreeManager> apz = mApz;
+  RunOnUpdaterThread(
+      aLayersId, NS_NewRunnableFunction("APZUpdater::SetTestAsyncZoom", [=]() {
+        RefPtr<AsyncPanZoomController> apzc =
+            apz->GetTargetAPZC(aLayersId, aScrollId);
+        if (apzc) {
+          apzc->SetTestAsyncZoom(aZoom);
+        } else {
+          NS_WARNING("Unable to find APZC in SetTestAsyncZoom");
+        }
+      }));
+}
+
+const WebRenderScrollData* APZUpdater::GetScrollData(LayersId aLayersId) const {
+  AssertOnUpdaterThread();
+  auto it = mScrollData.find(aLayersId);
+  return (it == mScrollData.end() ? nullptr : &(it->second));
+}
+
+void APZUpdater::AssertOnUpdaterThread() const {
+  if (APZThreadUtils::GetThreadAssertionsEnabled()) {
+    MOZ_ASSERT(IsUpdaterThread());
+  }
+}
+
+void APZUpdater::RunOnUpdaterThread(LayersId aLayersId,
+                                    already_AddRefed<Runnable> aTask) {
+  RefPtr<Runnable> task = aTask;
+
+  // In the scenario where IsConnectedToWebRender() is true, this function
+  // might get called early (before mUpdaterThreadId is set). In that case
+  // IsUpdaterThread() will return false and we'll queue the task onto
+  // mUpdaterQueue. This is fine; the task is still guaranteed to run (barring
+  // catastrophic failure) because the WakeSceneBuilder call will still trigger
+  // the callback to run tasks.
+
+  if (IsUpdaterThread()) {
+    // This function should only be called from the updater thread in test
+    // scenarios where we are not connected to WebRender. If it were called from
+    // the updater thread when we are connected to WebRender, running the task
+    // right away would be incorrect (we'd need to check that |aLayersId|
+    // isn't blocked, and if it is then enqueue the task instead).
+    MOZ_ASSERT(!IsConnectedToWebRender());
+    task->Run();
+    return;
+  }
+
+  if (IsConnectedToWebRender()) {
+    // If the updater thread is a WebRender thread, and we're not on it
+    // right now, save the task in the queue. We will run tasks from the queue
+    // during the callback from the updater thread, which we trigger by the
+    // call to WakeSceneBuilder.
+
+    bool sendWakeMessage = true;
+    {  // scope lock
+      MutexAutoLock lock(mQueueLock);
+      for (const auto& queuedTask : mUpdaterQueue) {
+        if (queuedTask.mLayersId == aLayersId) {
+          // If there's already a task in the queue with this layers id, then
+          // we must have previously sent a WakeSceneBuilder message (when
+          // adding the first task with this layers id to the queue). Either
+          // that hasn't been fully processed yet, or the layers id is blocked
+          // waiting for an epoch - in either case there's no point in sending
+          // another WakeSceneBuilder message.
+          sendWakeMessage = false;
+          break;
+        }
+      }
+      mUpdaterQueue.push_back(QueuedTask{aLayersId, task});
+    }
+    if (sendWakeMessage) {
+      RefPtr<wr::WebRenderAPI> api = mApz->GetWebRenderAPI();
+      if (api) {
+        api->WakeSceneBuilder();
+      } else {
+        // Not sure if this can happen, but it might be possible. If it does,
+        // the task is in the queue, but if we didn't get a WebRenderAPI it
+        // might never run, or it might run later if we manage to get a
+        // WebRenderAPI later. For now let's just emit a warning, this can
+        // probably be upgraded to an assert later.
+        NS_WARNING("Possibly dropping task posted to updater thread");
+      }
+    }
+    return;
+  }
+
+  if (CompositorThread()) {
+    CompositorThread()->Dispatch(task.forget());
+  } else {
+    // Could happen during startup
+    NS_WARNING("Dropping task posted to updater thread");
+  }
+}
+
+bool APZUpdater::IsUpdaterThread() const {
+  if (IsConnectedToWebRender()) {
+    // If the updater thread id isn't set yet then we cannot be running on the
+    // updater thread (because we will have the thread id before we run any
+    // C++ code on it, and this function is only ever invoked from C++ code),
+    // so return false in that scenario.
+    MutexAutoLock lock(mThreadIdLock);
+    return mUpdaterThreadId && PlatformThread::CurrentId() == *mUpdaterThreadId;
+  }
+  return CompositorThreadHolder::IsInCompositorThread();
+}
+
+void APZUpdater::RunOnControllerThread(LayersId aLayersId,
+                                       already_AddRefed<Runnable> aTask) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
+
+  RefPtr<Runnable> task = aTask;
+
+  RunOnUpdaterThread(
+      aLayersId,
+      NewRunnableFunction("APZUpdater::RunOnControllerThread",
+                          &APZThreadUtils::RunOnControllerThread,
+                          std::move(task), nsIThread::DISPATCH_NORMAL));
+}
+
+bool APZUpdater::IsConnectedToWebRender() const {
+  return mConnectedToWebRender;
+}
+
+/*static*/
+already_AddRefed<APZUpdater> APZUpdater::GetUpdater(
+    const wr::WrWindowId& aWindowId) {
+  RefPtr<APZUpdater> updater;
+  StaticMutexAutoLock lock(sWindowIdLock);
+  if (sWindowIdMap) {
+    auto it = sWindowIdMap->find(wr::AsUint64(aWindowId));
+    if (it != sWindowIdMap->end()) {
+      updater = it->second;
+    }
+  }
+  return updater.forget();
+}
+
+void APZUpdater::ProcessQueue() {
+  MOZ_ASSERT(!mDestroyed);
+
+  {  // scope lock to check for emptiness
+    MutexAutoLock lock(mQueueLock);
+    if (mUpdaterQueue.empty()) {
+      return;
+    }
+  }
+
+  std::deque<QueuedTask> blockedTasks;
+  while (true) {
+    QueuedTask task;
+
+    {  // scope lock to extract a task
+      MutexAutoLock lock(mQueueLock);
+      if (mUpdaterQueue.empty()) {
+        // If we're done processing mUpdaterQueue, swap the tasks that are
+        // still blocked back in and finish
+        std::swap(mUpdaterQueue, blockedTasks);
+        break;
+      }
+      task = mUpdaterQueue.front();
+      mUpdaterQueue.pop_front();
+    }
+
+    // We check the task to see if it is blocked. Note that while this
+    // ProcessQueue function is executing, a particular layers id cannot go
+    // from blocked to unblocked, because only CompleteSceneSwap can unblock
+    // a layers id, and that also runs on the updater thread. If somehow
+    // a layers id gets unblocked while we're processing the queue, then it
+    // might result in tasks getting executed out of order.
+
+    auto it = mEpochData.find(task.mLayersId);
+    if (it != mEpochData.end() && it->second.IsBlocked()) {
+      // If this task is blocked, put it into the blockedTasks queue that
+      // we will replace mUpdaterQueue with
+      blockedTasks.push_back(task);
+    } else {
+      // Run and discard the task
+      task.mRunnable->Run();
+    }
+  }
+
+  if (mDestroyed) {
+    // If we get here, then we must have just run the ClearTree task for
+    // this updater. There might be tasks in the queue from content subtrees
+    // of this window that are blocked due to stale epochs. This can happen
+    // if the tasks were queued after the root pipeline was removed in
+    // WebRender, which prevents scene builds (and therefore prevents us
+    // from getting updated epochs via CompleteSceneSwap). See bug 1465658
+    // comment 43 for some more context.
+    // To avoid leaking these tasks, we discard the contents of the queue.
+    // This happens during window shutdown so if we don't run the tasks it's
+    // not going to matter much.
+    MutexAutoLock lock(mQueueLock);
+    if (!mUpdaterQueue.empty()) {
+      mUpdaterQueue.clear();
+    }
+  }
+}
+
+void APZUpdater::MarkAsDetached(LayersId aLayersId) {
+  mApz->MarkAsDetached(aLayersId);
+}
+
+APZUpdater::EpochState::EpochState() : mRequired{0}, mIsRoot(false) {}
+
+bool APZUpdater::EpochState::IsBlocked() const {
+  // The root is a special case because we basically assume it is "visible"
+  // even before it is built for the first time. This is because building the
+  // scene automatically makes it visible, and we need to make sure the APZ
+  // scroll data gets applied atomically with that happening.
+  //
+  // Layer subtrees on the other hand do not automatically become visible upon
+  // being built, because there must be a another layer tree update to change
+  // the visibility (i.e. an ancestor layer tree update that adds the necessary
+  // reflayer to complete the chain of reflayers).
+  //
+  // So in the case of non-visible subtrees, we know that no hit-test will
+  // actually end up hitting that subtree either before or after the scene swap,
+  // because the subtree will remain non-visible. That in turns means that we
+  // can apply the APZ scroll data for that subtree epoch before the scene is
+  // built, because it's not going to get used anyway. And that means we don't
+  // need to block the queue for non-visible subtrees. Which is a good thing,
+  // because in practice it seems like we often have non-visible subtrees sent
+  // to the compositor from content.
+  if (mIsRoot && !mBuilt) {
+    return true;
+  }
+  return mBuilt && (*mBuilt < mRequired);
+}
+
+}  // namespace layers
+}  // namespace mozilla
+
+// Rust callback implementations
+
+void apz_register_updater(mozilla::wr::WrWindowId aWindowId) {
+  mozilla::layers::APZUpdater::SetUpdaterThread(aWindowId);
+}
+
+void apz_pre_scene_swap(mozilla::wr::WrWindowId aWindowId) {
+  mozilla::layers::APZUpdater::PrepareForSceneSwap(aWindowId);
+}
+
+void apz_post_scene_swap(mozilla::wr::WrWindowId aWindowId,
+                         const mozilla::wr::WrPipelineInfo* aInfo) {
+  mozilla::layers::APZUpdater::CompleteSceneSwap(aWindowId, *aInfo);
+}
+
+void apz_run_updater(mozilla::wr::WrWindowId aWindowId) {
+  mozilla::layers::APZUpdater::ProcessPendingTasks(aWindowId);
+}
+
+void apz_deregister_updater(mozilla::wr::WrWindowId aWindowId) {
+  // Run anything that's still left.
+  mozilla::layers::APZUpdater::ProcessPendingTasks(aWindowId);
+}