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* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <stdint.h>
#include <sys/types.h>
#include <utils/Errors.h>
#include <utils/RefBase.h>
#include <utils/Timers.h>
#include <binder/IInterface.h>
#include <gui/ISurfaceComposer.h>
// ----------------------------------------------------------------------------
namespace android {
// ----------------------------------------------------------------------------
class IDisplayEventConnection;
namespace gui {
class BitTube;
} // namespace gui
static inline constexpr uint32_t fourcc(char c1, char c2, char c3, char c4) {
return static_cast<uint32_t>(c1) << 24 |
static_cast<uint32_t>(c2) << 16 |
static_cast<uint32_t>(c3) << 8 |
// ----------------------------------------------------------------------------
class DisplayEventReceiver {
enum {
DISPLAY_EVENT_VSYNC = fourcc('v', 's', 'y', 'n'),
DISPLAY_EVENT_HOTPLUG = fourcc('p', 'l', 'u', 'g'),
DISPLAY_EVENT_CONFIG_CHANGED = fourcc('c', 'o', 'n', 'f'),
DISPLAY_EVENT_NULL = fourcc('n', 'u', 'l', 'l'),
struct Event {
struct Header {
uint32_t type;
PhysicalDisplayId displayId;
nsecs_t timestamp __attribute__((aligned(8)));
struct VSync {
uint32_t count;
nsecs_t expectedVSyncTimestamp;
struct Hotplug {
bool connected;
struct Config {
int32_t configId;
nsecs_t vsyncPeriod;
Header header;
union {
VSync vsync;
Hotplug hotplug;
Config config;
* DisplayEventReceiver creates and registers an event connection with
* SurfaceFlinger. VSync events are disabled by default. Call setVSyncRate
* or requestNextVsync to receive them.
* To receive Config Changed events specify this in the constructor.
* Other events start being delivered immediately.
explicit DisplayEventReceiver(
ISurfaceComposer::VsyncSource vsyncSource = ISurfaceComposer::eVsyncSourceApp,
ISurfaceComposer::ConfigChanged configChanged =
* ~DisplayEventReceiver severs the connection with SurfaceFlinger, new events
* stop being delivered immediately. Note that the queue could have
* some events pending. These will be delivered.
* initCheck returns the state of DisplayEventReceiver after construction.
status_t initCheck() const;
* getFd returns the file descriptor to use to receive events.
* OWNERSHIP IS RETAINED by DisplayEventReceiver. DO NOT CLOSE this
* file-descriptor.
int getFd() const;
* getEvents reads events from the queue and returns how many events were
* read. Returns 0 if there are no more events or a negative error code.
* If NOT_ENOUGH_DATA is returned, the object has become invalid forever, it
* should be destroyed and getEvents() shouldn't be called again.
ssize_t getEvents(Event* events, size_t count);
static ssize_t getEvents(gui::BitTube* dataChannel, Event* events, size_t count);
* sendEvents write events to the queue and returns how many events were
* written.
ssize_t sendEvents(Event const* events, size_t count);
static ssize_t sendEvents(gui::BitTube* dataChannel, Event const* events, size_t count);
* setVsyncRate() sets the Event::VSync delivery rate. A value of
* 1 returns every Event::VSync. A value of 2 returns every other event,
* etc... a value of 0 returns no event unless requestNextVsync() has
* been called.
status_t setVsyncRate(uint32_t count);
* requestNextVsync() schedules the next Event::VSync. It has no effect
* if the vsync rate is > 0.
status_t requestNextVsync();
sp<IDisplayEventConnection> mEventConnection;
std::unique_ptr<gui::BitTube> mDataChannel;
// ----------------------------------------------------------------------------
}; // namespace android