DisplayEventReceiver.h revision c2b9017b595ed146aae181f0efc46c169ea86806 
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
29// ----------------------------------------------------------------------------
30
31namespace android {
32
33// ----------------------------------------------------------------------------
34
35class BitTube;
36class IDisplayEventConnection;
37
38static inline constexpr uint32_t fourcc(char c1, char c2, char c3, char c4) {
39    return static_cast<uint32_t>(c1) << 24 |
40        static_cast<uint32_t>(c2) << 16 |
41        static_cast<uint32_t>(c3) << 8 |
42        static_cast<uint32_t>(c4);
43}
44
45// ----------------------------------------------------------------------------
46class DisplayEventReceiver {
47public:
48    enum {
49        DISPLAY_EVENT_VSYNC = fourcc('v', 's', 'y', 'n'),
50        DISPLAY_EVENT_HOTPLUG = fourcc('p', 'l', 'u', 'g'),
51    };
52
53    struct Event {
54
55        struct Header {
56            uint32_t type;
57            uint32_t id;
58            nsecs_t timestamp __attribute__((aligned(8)));
59        };
60
61        struct VSync {
62            uint32_t count;
63        };
64
65        struct Hotplug {
66            bool connected;
67        };
68
69        Header header;
70        union {
71            VSync vsync;
72            Hotplug hotplug;
73        };
74    };
75
76public:
77    /*
78     * DisplayEventReceiver creates and registers an event connection with
79     * SurfaceFlinger. VSync events are disabled by default. Call setVSyncRate
80     * or requestNextVsync to receive them.
81     * Other events start being delivered immediately.
82     */
83    DisplayEventReceiver();
84
85    /*
86     * ~DisplayEventReceiver severs the connection with SurfaceFlinger, new events
87     * stop being delivered immediately. Note that the queue could have
88     * some events pending. These will be delivered.
89     */
90    ~DisplayEventReceiver();
91
92    /*
93     * initCheck returns the state of DisplayEventReceiver after construction.
94     */
95    status_t initCheck() const;
96
97    /*
98     * getFd returns the file descriptor to use to receive events.
99     * OWNERSHIP IS RETAINED by DisplayEventReceiver. DO NOT CLOSE this
100     * file-descriptor.
101     */
102    int getFd() const;
103
104    /*
105     * getEvents reads events from the queue and returns how many events were
106     * read. Returns 0 if there are no more events or a negative error code.
107     * If NOT_ENOUGH_DATA is returned, the object has become invalid forever, it
108     * should be destroyed and getEvents() shouldn't be called again.
109     */
110    ssize_t getEvents(Event* events, size_t count);
111    static ssize_t getEvents(const sp<BitTube>& dataChannel,
112            Event* events, size_t count);
113
114    /*
115     * sendEvents write events to the queue and returns how many events were
116     * written.
117     */
118    static ssize_t sendEvents(const sp<BitTube>& dataChannel,
119            Event const* events, size_t count);
120
121    /*
122     * setVsyncRate() sets the Event::VSync delivery rate. A value of
123     * 1 returns every Event::VSync. A value of 2 returns every other event,
124     * etc... a value of 0 returns no event unless  requestNextVsync() has
125     * been called.
126     */
127    status_t setVsyncRate(uint32_t count);
128
129    /*
130     * requestNextVsync() schedules the next Event::VSync. It has no effect
131     * if the vsync rate is > 0.
132     */
133    status_t requestNextVsync();
134
135private:
136    sp<IDisplayEventConnection> mEventConnection;
137    sp<BitTube> mDataChannel;
138};
139
140// ----------------------------------------------------------------------------
141}; // namespace android
142
143#endif // ANDROID_GUI_DISPLAY_EVENT_H
144