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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ANDROID_GUI_DISPLAY_EVENT_H
     18 #define ANDROID_GUI_DISPLAY_EVENT_H
     19 
     20 #include <stdint.h>
     21 #include <sys/types.h>
     22 
     23 #include <utils/Errors.h>
     24 #include <utils/RefBase.h>
     25 #include <utils/Timers.h>
     26 
     27 #include <binder/IInterface.h>
     28 #include <gui/ISurfaceComposer.h>
     29 
     30 // ----------------------------------------------------------------------------
     31 
     32 namespace android {
     33 
     34 // ----------------------------------------------------------------------------
     35 
     36 class IDisplayEventConnection;
     37 
     38 namespace gui {
     39 class BitTube;
     40 } // namespace gui
     41 
     42 static inline constexpr uint32_t fourcc(char c1, char c2, char c3, char c4) {
     43     return static_cast<uint32_t>(c1) << 24 |
     44         static_cast<uint32_t>(c2) << 16 |
     45         static_cast<uint32_t>(c3) << 8 |
     46         static_cast<uint32_t>(c4);
     47 }
     48 
     49 // ----------------------------------------------------------------------------
     50 class DisplayEventReceiver {
     51 public:
     52     enum {
     53         DISPLAY_EVENT_VSYNC = fourcc('v', 's', 'y', 'n'),
     54         DISPLAY_EVENT_HOTPLUG = fourcc('p', 'l', 'u', 'g'),
     55         DISPLAY_EVENT_CONFIG_CHANGED = fourcc('c', 'o', 'n', 'f'),
     56     };
     57 
     58     struct Event {
     59 
     60         struct Header {
     61             uint32_t type;
     62             PhysicalDisplayId displayId;
     63             nsecs_t timestamp __attribute__((aligned(8)));
     64         };
     65 
     66         struct VSync {
     67             uint32_t count;
     68         };
     69 
     70         struct Hotplug {
     71             bool connected;
     72         };
     73 
     74         struct Config {
     75             int32_t configId;
     76         };
     77 
     78         Header header;
     79         union {
     80             VSync vsync;
     81             Hotplug hotplug;
     82             Config config;
     83         };
     84     };
     85 
     86 public:
     87     /*
     88      * DisplayEventReceiver creates and registers an event connection with
     89      * SurfaceFlinger. VSync events are disabled by default. Call setVSyncRate
     90      * or requestNextVsync to receive them.
     91      * Other events start being delivered immediately.
     92      */
     93     explicit DisplayEventReceiver(
     94             ISurfaceComposer::VsyncSource vsyncSource = ISurfaceComposer::eVsyncSourceApp);
     95 
     96     /*
     97      * ~DisplayEventReceiver severs the connection with SurfaceFlinger, new events
     98      * stop being delivered immediately. Note that the queue could have
     99      * some events pending. These will be delivered.
    100      */
    101     ~DisplayEventReceiver();
    102 
    103     /*
    104      * initCheck returns the state of DisplayEventReceiver after construction.
    105      */
    106     status_t initCheck() const;
    107 
    108     /*
    109      * getFd returns the file descriptor to use to receive events.
    110      * OWNERSHIP IS RETAINED by DisplayEventReceiver. DO NOT CLOSE this
    111      * file-descriptor.
    112      */
    113     int getFd() const;
    114 
    115     /*
    116      * getEvents reads events from the queue and returns how many events were
    117      * read. Returns 0 if there are no more events or a negative error code.
    118      * If NOT_ENOUGH_DATA is returned, the object has become invalid forever, it
    119      * should be destroyed and getEvents() shouldn't be called again.
    120      */
    121     ssize_t getEvents(Event* events, size_t count);
    122     static ssize_t getEvents(gui::BitTube* dataChannel, Event* events, size_t count);
    123 
    124     /*
    125      * sendEvents write events to the queue and returns how many events were
    126      * written.
    127      */
    128     static ssize_t sendEvents(gui::BitTube* dataChannel, Event const* events, size_t count);
    129 
    130     /*
    131      * setVsyncRate() sets the Event::VSync delivery rate. A value of
    132      * 1 returns every Event::VSync. A value of 2 returns every other event,
    133      * etc... a value of 0 returns no event unless  requestNextVsync() has
    134      * been called.
    135      */
    136     status_t setVsyncRate(uint32_t count);
    137 
    138     /*
    139      * requestNextVsync() schedules the next Event::VSync. It has no effect
    140      * if the vsync rate is > 0.
    141      */
    142     status_t requestNextVsync();
    143 
    144 private:
    145     sp<IDisplayEventConnection> mEventConnection;
    146     std::unique_ptr<gui::BitTube> mDataChannel;
    147 };
    148 
    149 // ----------------------------------------------------------------------------
    150 }; // namespace android
    151 
    152 #endif // ANDROID_GUI_DISPLAY_EVENT_H
    153