DisplayEventReceiver.h revision 3cf199aef6250552555344944c3e3a6e4ab05f92 
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
38// ----------------------------------------------------------------------------
39
40class DisplayEventReceiver {
41public:
42    enum {
43        DISPLAY_EVENT_VSYNC = 'vsyn'
44    };
45
46    struct Event {
47
48        struct Header {
49            uint32_t type;
50            nsecs_t timestamp;
51        };
52
53        struct VSync {
54            uint32_t count;
55        };
56
57        Header header;
58        union {
59            VSync vsync;
60        };
61    };
62
63public:
64    /*
65     * DisplayEventReceiver creates and registers an event connection with
66     * SurfaceFlinger. VSync events are disabled by default. Call setVSyncRate
67     * or requestNextVsync to receive them.
68     * Other events start being delivered immediately.
69     */
70    DisplayEventReceiver();
71
72    /*
73     * ~DisplayEventReceiver severs the connection with SurfaceFlinger, new events
74     * stop being delivered immediately. Note that the queue could have
75     * some events pending. These will be delivered.
76     */
77    ~DisplayEventReceiver();
78
79    /*
80     * initCheck returns the state of DisplayEventReceiver after construction.
81     */
82    status_t initCheck() const;
83
84    /*
85     * getFd returns the file descriptor to use to receive events.
86     * OWNERSHIP IS RETAINED by DisplayEventReceiver. DO NOT CLOSE this
87     * file-descriptor.
88     */
89    int getFd() const;
90
91    /*
92     * getEvents reads event from the queue and returns how many events were
93     * read. Returns 0 if there are no more events or a negative error code.
94     * If NOT_ENOUGH_DATA is returned, the object has become invalid forever, it
95     * should be destroyed and getEvents() shouldn't be called again.
96     */
97    ssize_t getEvents(Event* events, size_t count);
98
99    /*
100     * setVsyncRate() sets the Event::VSync delivery rate. A value of
101     * 1 returns every Event::VSync. A value of 2 returns every other event,
102     * etc... a value of 0 returns no event unless  requestNextVsync() has
103     * been called.
104     */
105    status_t setVsyncRate(uint32_t count);
106
107    /*
108     * requestNextVsync() schedules the next Event::VSync. It has no effect
109     * if the vsync rate is > 0.
110     */
111    status_t requestNextVsync();
112
113private:
114    sp<IDisplayEventConnection> mEventConnection;
115    sp<BitTube> mDataChannel;
116};
117
118// ----------------------------------------------------------------------------
119}; // namespace android
120
121#endif // ANDROID_GUI_DISPLAY_EVENT_H
122