Add support for sending VSYNC events to the framework

use gui/DisplayEvent to receive the events. Events are
dispatched through a unix pipe, so the API is compatible
with utils/Looper. see gui/DisplayEvent.h for more info.

Bug: 1475048
Change-Id: Ia720f64d1b950328b47b22c6a86042e481d35f09

1 files changed, 83 insertions, 0 deletions

diff --git a/libs/gui/DisplayEventReceiver.cpp b/libs/gui/DisplayEventReceiver.cpp
new file mode 100644
index 0000000000..3b29a113e4
--- /dev/null
+++ b/libs/gui/DisplayEventReceiver.cpp
@@ -0,0 +1,83 @@
+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <string.h>
+
+#include <utils/Errors.h>
+
+#include <gui/BitTube.h>
+#include <gui/DisplayEventReceiver.h>
+#include <gui/IDisplayEventConnection.h>
+
+#include <private/gui/ComposerService.h>
+
+#include <surfaceflinger/ISurfaceComposer.h>
+
+// ---------------------------------------------------------------------------
+
+namespace android {
+
+// ---------------------------------------------------------------------------
+
+DisplayEventReceiver::DisplayEventReceiver() {
+    sp<ISurfaceComposer> sf(ComposerService::getComposerService());
+    if (sf != NULL) {
+        mEventConnection = sf->createDisplayEventConnection();
+        if (mEventConnection != NULL) {
+            mDataChannel = mEventConnection->getDataChannel();
+        }
+    }
+}
+
+DisplayEventReceiver::~DisplayEventReceiver() {
+}
+
+status_t DisplayEventReceiver::initCheck() const {
+    if (mDataChannel != NULL)
+        return NO_ERROR;
+    return NO_INIT;
+}
+
+int DisplayEventReceiver::getFd() const {
+    if (mDataChannel == NULL)
+        return NO_INIT;
+
+    return mDataChannel->getFd();
+}
+
+ssize_t DisplayEventReceiver::getEvents(DisplayEventReceiver::Event* events,
+        size_t count) {
+    ssize_t size = mDataChannel->read(events, sizeof(events[0])*count);
+    LOGE_IF(size<0,
+            "DisplayEventReceiver::getEvents error (%s)",
+            strerror(-size));
+    if (size >= 0) {
+        // Note: if (size % sizeof(events[0])) != 0, we've got a
+        // partial read. This can happen if the queue filed up (ie: if we
+        // didn't pull from it fast enough).
+        // We discard the partial event and rely on the sender to
+        // re-send the event if appropriate (some events, like VSYNC
+        // can be lost forever).
+
+        // returns number of events read
+        size /= sizeof(events[0]);
+    }
+    return size;
+}
+
+// ---------------------------------------------------------------------------
+
+}; // namespace android