1 files changed, 160 insertions, 0 deletions
diff --git a/gfx/thebes/VsyncSource.cpp b/gfx/thebes/VsyncSource.cpp
new file mode 100644
index 0000000000..d7cfb339aa
--- /dev/null
+++ b/gfx/thebes/VsyncSource.cpp
@@ -0,0 +1,160 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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 "VsyncSource.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+#include "mozilla/VsyncDispatcher.h"
+#include "MainThreadUtils.h"
+#include "gfxPlatform.h"
+
+#ifdef MOZ_WAYLAND
+#  include "WaylandVsyncSource.h"
+#endif
+
+namespace mozilla {
+namespace gfx {
+
+VsyncSource::VsyncSource() : mState("VsyncSource::State") {
+  MOZ_ASSERT(NS_IsMainThread());
+}
+
+VsyncSource::~VsyncSource() { MOZ_ASSERT(NS_IsMainThread()); }
+
+// Called on the vsync thread
+void VsyncSource::NotifyVsync(const TimeStamp& aVsyncTimestamp,
+                              const TimeStamp& aOutputTimestamp) {
+  VsyncId vsyncId;
+  nsTArray<DispatcherRefWithCount> dispatchers;
+
+  {
+    auto state = mState.Lock();
+    vsyncId = state->mVsyncId.Next();
+    dispatchers = state->mDispatchers.Clone();
+    state->mVsyncId = vsyncId;
+  }
+
+  // Notify our listeners, outside of the lock.
+  const VsyncEvent event(vsyncId, aVsyncTimestamp, aOutputTimestamp);
+  for (const auto& dispatcher : dispatchers) {
+    dispatcher.mDispatcher->NotifyVsync(event);
+  }
+}
+
+void VsyncSource::AddVsyncDispatcher(VsyncDispatcher* aVsyncDispatcher) {
+  MOZ_ASSERT(aVsyncDispatcher);
+  {
+    auto state = mState.Lock();
+
+    // Find the dispatcher in mDispatchers. If it is already present, increment
+    // the count. If not, add it with a count of 1.
+    bool found = false;
+    for (auto& dispatcherRefWithCount : state->mDispatchers) {
+      if (dispatcherRefWithCount.mDispatcher == aVsyncDispatcher) {
+        dispatcherRefWithCount.mCount++;
+        found = true;
+        break;
+      }
+    }
+    if (!found) {
+      state->mDispatchers.AppendElement(
+          DispatcherRefWithCount{aVsyncDispatcher, 1});
+    }
+  }
+
+  UpdateVsyncStatus();
+}
+
+void VsyncSource::RemoveVsyncDispatcher(VsyncDispatcher* aVsyncDispatcher) {
+  MOZ_ASSERT(aVsyncDispatcher);
+  {
+    auto state = mState.Lock();
+
+    // Find the dispatcher in mDispatchers. If found, decrement the count.
+    // If the count becomes zero, remove it from mDispatchers.
+    for (auto it = state->mDispatchers.begin(); it != state->mDispatchers.end();
+         ++it) {
+      if (it->mDispatcher == aVsyncDispatcher) {
+        it->mCount--;
+        if (it->mCount == 0) {
+          state->mDispatchers.RemoveElementAt(it);
+        }
+        break;
+      }
+    }
+
+    // In the future we should probably MOZ_RELEASE_ASSERT here that we don't
+    // try to remove a dispatcher which isn't in mDispatchers.
+  }
+
+  UpdateVsyncStatus();
+}
+
+// This is the base class implementation. Subclasses override this method.
+TimeDuration VsyncSource::GetVsyncRate() {
+  // If hardware queries fail / are unsupported, we have to just guess.
+  return TimeDuration::FromMilliseconds(1000.0 / 60.0);
+}
+
+void VsyncSource::UpdateVsyncStatus() {
+  if (!NS_IsMainThread()) {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "VsyncSource::UpdateVsyncStatus",
+        [self = RefPtr{this}] { self->UpdateVsyncStatus(); }));
+    return;
+  }
+
+  MOZ_ASSERT(NS_IsMainThread());
+  // WARNING: This function SHOULD NOT BE CALLED WHILE HOLDING LOCKS
+  // NotifyVsync grabs a lock to dispatch vsync events
+  // When disabling vsync, we wait for the underlying thread to stop on some
+  // platforms We can deadlock if we wait for the underlying vsync thread to
+  // stop while the vsync thread is in NotifyVsync.
+  bool enableVsync = false;
+  {  // scope lock
+    auto state = mState.Lock();
+    enableVsync = !state->mDispatchers.IsEmpty();
+  }
+
+  if (enableVsync) {
+    EnableVsync();
+  } else {
+    DisableVsync();
+  }
+
+  if (IsVsyncEnabled() != enableVsync) {
+    NS_WARNING("Vsync status did not change.");
+  }
+}
+
+// static
+Maybe<TimeDuration> VsyncSource::GetFastestVsyncRate() {
+  Maybe<TimeDuration> retVal;
+  if (!gfxPlatform::Initialized()) {
+    return retVal;
+  }
+
+  RefPtr<VsyncDispatcher> vsyncDispatcher =
+      gfxPlatform::GetPlatform()->GetGlobalVsyncDispatcher();
+  RefPtr<VsyncSource> vsyncSource = vsyncDispatcher->GetCurrentVsyncSource();
+  if (vsyncSource->IsVsyncEnabled()) {
+    retVal.emplace(vsyncSource->GetVsyncRate());
+#ifdef MOZ_WAYLAND
+    Maybe<TimeDuration> waylandRate = WaylandVsyncSource::GetFastestVsyncRate();
+    if (waylandRate) {
+      if (!retVal) {
+        retVal.emplace(*waylandRate);
+      } else if (*waylandRate < *retVal) {
+        retVal = waylandRate;
+      }
+    }
+#endif
+  }
+
+  return retVal;
+}
+
+}  // namespace gfx
+}  // namespace mozilla