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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     };
     56 
     57     struct Event {
     58 
     59         struct Header {
     60             uint32_t type;
     61             uint32_t id;
     62             nsecs_t timestamp __attribute__((aligned(8)));
     63         };
     64 
     65         struct VSync {
     66             uint32_t count;
     67         };
     68 
     69         struct Hotplug {
     70             bool connected;
     71         };
     72 
     73         Header header;
     74         union {
     75             VSync vsync;
     76             Hotplug hotplug;
     77         };
     78     };
     79 
     80 public:
     81     /*
     82      * DisplayEventReceiver creates and registers an event connection with
     83      * SurfaceFlinger. VSync events are disabled by default. Call setVSyncRate
     84      * or requestNextVsync to receive them.
     85      * Other events start being delivered immediately.
     86      */
     87     DisplayEventReceiver(
     88             ISurfaceComposer::VsyncSource vsyncSource = ISurfaceComposer::eVsyncSourceApp);
     89 
     90     /*
     91      * ~DisplayEventReceiver severs the connection with SurfaceFlinger, new events
     92      * stop being delivered immediately. Note that the queue could have
     93      * some events pending. These will be delivered.
     94      */
     95     ~DisplayEventReceiver();
     96 
     97     /*
     98      * initCheck returns the state of DisplayEventReceiver after construction.
     99      */
    100     status_t initCheck() const;
    101 
    102     /*
    103      * getFd returns the file descriptor to use to receive events.
    104      * OWNERSHIP IS RETAINED by DisplayEventReceiver. DO NOT CLOSE this
    105      * file-descriptor.
    106      */
    107     int getFd() const;
    108 
    109     /*
    110      * getEvents reads events from the queue and returns how many events were
    111      * read. Returns 0 if there are no more events or a negative error code.
    112      * If NOT_ENOUGH_DATA is returned, the object has become invalid forever, it
    113      * should be destroyed and getEvents() shouldn't be called again.
    114      */
    115     ssize_t getEvents(Event* events, size_t count);
    116     static ssize_t getEvents(gui::BitTube* dataChannel, Event* events, size_t count);
    117 
    118     /*
    119      * sendEvents write events to the queue and returns how many events were
    120      * written.
    121      */
    122     static ssize_t sendEvents(gui::BitTube* dataChannel, Event const* events, size_t count);
    123 
    124     /*
    125      * setVsyncRate() sets the Event::VSync delivery rate. A value of
    126      * 1 returns every Event::VSync. A value of 2 returns every other event,
    127      * etc... a value of 0 returns no event unless  requestNextVsync() has
    128      * been called.
    129      */
    130     status_t setVsyncRate(uint32_t count);
    131 
    132     /*
    133      * requestNextVsync() schedules the next Event::VSync. It has no effect
    134      * if the vsync rate is > 0.
    135      */
    136     status_t requestNextVsync();
    137 
    138 private:
    139     sp<IDisplayEventConnection> mEventConnection;
    140     std::unique_ptr<gui::BitTube> mDataChannel;
    141 };
    142 
    143 // ----------------------------------------------------------------------------
    144 }; // namespace android
    145 
    146 #endif // ANDROID_GUI_DISPLAY_EVENT_H
    147