1 files changed, 76 insertions, 0 deletions
diff --git a/xpcom/threads/MainThreadIdlePeriod.cpp b/xpcom/threads/MainThreadIdlePeriod.cpp
new file mode 100644
index 000000000..4a5f99dd7
--- /dev/null
+++ b/xpcom/threads/MainThreadIdlePeriod.cpp
@@ -0,0 +1,76 @@
+/* -*- 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 "MainThreadIdlePeriod.h"
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Preferences.h"
+#include "nsRefreshDriver.h"
+
+#define DEFAULT_LONG_IDLE_PERIOD 50.0f
+#define DEFAULT_MIN_IDLE_PERIOD 3.0f
+
+namespace mozilla {
+
+NS_IMETHODIMP
+MainThreadIdlePeriod::GetIdlePeriodHint(TimeStamp* aIdleDeadline)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aIdleDeadline);
+
+  Maybe<TimeStamp> deadline = nsRefreshDriver::GetIdleDeadlineHint();
+
+  if (deadline.isSome()) {
+    // If the idle period is too small, then just return a null time
+    // to indicate we are busy. Otherwise return the actual deadline.
+    TimeDuration minIdlePeriod =
+      TimeDuration::FromMilliseconds(GetMinIdlePeriod());
+    bool busySoon = deadline.value().IsNull() ||
+                    (TimeStamp::Now() >= (deadline.value() - minIdlePeriod));
+    *aIdleDeadline = busySoon ? TimeStamp() : deadline.value();
+  } else {
+    *aIdleDeadline =
+      TimeStamp::Now() + TimeDuration::FromMilliseconds(GetLongIdlePeriod());
+  }
+
+  return NS_OK;
+}
+
+/* static */ float
+MainThreadIdlePeriod::GetLongIdlePeriod()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  static float sLongIdlePeriod = DEFAULT_LONG_IDLE_PERIOD;
+  static bool sInitialized = false;
+
+  if (!sInitialized && Preferences::IsServiceAvailable()) {
+    sInitialized = true;
+    Preferences::AddFloatVarCache(&sLongIdlePeriod, "idle_queue.long_period",
+                                  DEFAULT_LONG_IDLE_PERIOD);
+  }
+
+  return sLongIdlePeriod;
+}
+
+/* static */ float
+MainThreadIdlePeriod::GetMinIdlePeriod()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  static float sMinIdlePeriod = DEFAULT_MIN_IDLE_PERIOD;
+  static bool sInitialized = false;
+
+  if (!sInitialized && Preferences::IsServiceAvailable()) {
+    sInitialized = true;
+    Preferences::AddFloatVarCache(&sMinIdlePeriod, "idle_queue.min_period",
+                                  DEFAULT_MIN_IDLE_PERIOD);
+  }
+
+  return sMinIdlePeriod;
+}
+
+} // namespace mozilla