VirtualDisplaySurface.h revision 1e27ba234c5bfd4f6535ee221a6c20407a50f868 
1/*
2 * Copyright 2013 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_SF_VIRTUAL_DISPLAY_SURFACE_H
18#define ANDROID_SF_VIRTUAL_DISPLAY_SURFACE_H
19
20#include <gui/ConsumerBase.h>
21#include <gui/IGraphicBufferProducer.h>
22
23#include "DisplaySurface.h"
24
25// ---------------------------------------------------------------------------
26namespace android {
27// ---------------------------------------------------------------------------
28
29class HWComposer;
30
31/* This DisplaySurface implementation supports virtual displays, where GLES
32 * and/or HWC compose into a buffer that is then passed to an arbitrary
33 * consumer (the sink) running in another process.
34 *
35 * The simplest case is when the virtual display will never use the h/w
36 * composer -- either the h/w composer doesn't support writing to buffers, or
37 * there are more virtual displays than it supports simultaneously. In this
38 * case, the GLES driver works directly with the output buffer queue, and
39 * calls to the VirtualDisplay from SurfaceFlinger and DisplayHardware do
40 * nothing.
41 *
42 * If h/w composer might be used, then each frame will fall into one of three
43 * configurations: GLES-only, HWC-only, and MIXED composition. In all of these,
44 * we must provide a FB target buffer and output buffer for the HWC set() call.
45 *
46 * In GLES-only composition, the GLES driver is given a buffer from the sink to
47 * render into. When the GLES driver queues the buffer to the
48 * VirtualDisplaySurface, the VirtualDisplaySurface holds onto it instead of
49 * immediately queueing it to the sink. The buffer is used as both the FB
50 * target and output buffer for HWC, though on these frames the HWC doesn't
51 * do any work for this display and doesn't write to the output buffer. After
52 * composition is complete, the buffer is queued to the sink.
53 *
54 * In HWC-only composition, the VirtualDisplaySurface dequeues a buffer from
55 * the sink and passes it to HWC as both the FB target buffer and output
56 * buffer. The HWC doesn't need to read from the FB target buffer, but does
57 * write to the output buffer. After composition is complete, the buffer is
58 * queued to the sink.
59 *
60 * On MIXED frames, things become more complicated, since some h/w composer
61 * implementations can't read from and write to the same buffer. This class has
62 * an internal BufferQueue that it uses as a scratch buffer pool. The GLES
63 * driver is given a scratch buffer to render into. When it finishes rendering,
64 * the buffer is queued and then immediately acquired by the
65 * VirtualDisplaySurface. The scratch buffer is then used as the FB target
66 * buffer for HWC, and a separate buffer is dequeued from the sink and used as
67 * the HWC output buffer. When HWC composition is complete, the scratch buffer
68 * is released and the output buffer is queued to the sink.
69 */
70class VirtualDisplaySurface : public DisplaySurface,
71                              public BnGraphicBufferProducer,
72                              private ConsumerBase {
73public:
74    VirtualDisplaySurface(HWComposer& hwc, int32_t dispId,
75            const sp<IGraphicBufferProducer>& sink,
76            const sp<BufferQueue>& bq,
77            const String8& name);
78
79    //
80    // DisplaySurface interface
81    //
82    virtual status_t beginFrame();
83    virtual status_t prepareFrame(CompositionType compositionType);
84    virtual status_t compositionComplete();
85    virtual status_t advanceFrame();
86    virtual void onFrameCommitted();
87    virtual void dump(String8& result) const;
88
89private:
90    enum Source {SOURCE_SINK = 0, SOURCE_SCRATCH = 1};
91
92    virtual ~VirtualDisplaySurface();
93
94    //
95    // IGraphicBufferProducer interface, used by the GLES driver.
96    //
97    virtual status_t requestBuffer(int pslot, sp<GraphicBuffer>* outBuf);
98    virtual status_t setBufferCount(int bufferCount);
99    virtual status_t dequeueBuffer(int* pslot, sp<Fence>* fence, bool async,
100            uint32_t w, uint32_t h, uint32_t format, uint32_t usage);
101    virtual status_t queueBuffer(int pslot,
102            const QueueBufferInput& input, QueueBufferOutput* output);
103    virtual void cancelBuffer(int pslot, const sp<Fence>& fence);
104    virtual int query(int what, int* value);
105    virtual status_t connect(const sp<IBinder>& token,
106            int api, bool producerControlledByApp, QueueBufferOutput* output);
107    virtual status_t disconnect(int api);
108
109    //
110    // Utility methods
111    //
112    static Source fbSourceForCompositionType(CompositionType type);
113    status_t dequeueBuffer(Source source, uint32_t format, uint32_t usage,
114            int* sslot, sp<Fence>* fence);
115    void updateQueueBufferOutput(const QueueBufferOutput& qbo);
116    void resetPerFrameState();
117    status_t refreshOutputBuffer();
118
119    // Both the sink and scratch buffer pools have their own set of slots
120    // ("source slots", or "sslot"). We have to merge these into the single
121    // set of slots used by the GLES producer ("producer slots" or "pslot") and
122    // internally in the VirtualDisplaySurface. To minimize the number of times
123    // a producer slot switches which source it comes from, we map source slot
124    // numbers to producer slot numbers differently for each source.
125    static int mapSource2ProducerSlot(Source source, int sslot);
126    static int mapProducer2SourceSlot(Source source, int pslot);
127
128    //
129    // Immutable after construction
130    //
131    HWComposer& mHwc;
132    const int32_t mDisplayId;
133    const String8 mDisplayName;
134    sp<IGraphicBufferProducer> mSource[2]; // indexed by SOURCE_*
135
136    //
137    // Inter-frame state
138    //
139
140    // To avoid buffer reallocations, we track the buffer usage and format
141    // we used on the previous frame and use it again on the new frame. If
142    // the composition type changes or the GLES driver starts requesting
143    // different usage/format, we'll get a new buffer.
144    uint32_t mOutputFormat;
145    uint32_t mOutputUsage;
146
147    // Since we present a single producer interface to the GLES driver, but
148    // are internally muxing between the sink and scratch producers, we have
149    // to keep track of which source last returned each producer slot from
150    // dequeueBuffer. Each bit in mLastSlotSource corresponds to a producer
151    // slot. Both mProducerSlotSource and mProducerBuffers are indexed by a
152    // "producer slot"; see the mapSlot*() functions.
153    uint32_t mProducerSlotSource;
154    sp<GraphicBuffer> mProducerBuffers[BufferQueue::NUM_BUFFER_SLOTS];
155
156    // The QueueBufferOutput with the latest info from the sink, and with the
157    // transform hint cleared. Since we defer queueBuffer from the GLES driver
158    // to the sink, we have to return the previous version.
159    QueueBufferOutput mQueueBufferOutput;
160
161    //
162    // Intra-frame state
163    //
164
165    // Composition type and GLES buffer source for the current frame.
166    // Valid after prepareFrame(), cleared in onFrameCommitted.
167    CompositionType mCompositionType;
168
169    // Details of the current sink buffer. These become valid when a buffer is
170    // dequeued from the sink, and are used when queueing the buffer.
171    uint32_t mSinkBufferWidth, mSinkBufferHeight;
172
173    // mFbFence is the fence HWC should wait for before reading the framebuffer
174    // target buffer.
175    sp<Fence> mFbFence;
176
177    // mOutputFence is the fence HWC should wait for before writing to the
178    // output buffer.
179    sp<Fence> mOutputFence;
180
181    // Producer slot numbers for the buffers to use for HWC framebuffer target
182    // and output.
183    int mFbProducerSlot;
184    int mOutputProducerSlot;
185
186    // Debug only -- track the sequence of events in each frame so we can make
187    // sure they happen in the order we expect. This class implicitly models
188    // a state machine; this enum/variable makes it explicit.
189    //
190    // +-----------+-------------------+-------------+
191    // | State     | Event             || Next State |
192    // +-----------+-------------------+-------------+
193    // | IDLE      | beginFrame        || BEGUN      |
194    // | BEGUN     | prepareFrame      || PREPARED   |
195    // | PREPARED  | dequeueBuffer [1] || GLES       |
196    // | PREPARED  | advanceFrame [2]  || HWC        |
197    // | GLES      | queueBuffer       || GLES_DONE  |
198    // | GLES_DONE | advanceFrame      || HWC        |
199    // | HWC       | onFrameCommitted  || IDLE       |
200    // +-----------+-------------------++------------+
201    // [1] COMPOSITION_GLES and COMPOSITION_MIXED frames.
202    // [2] COMPOSITION_HWC frames.
203    //
204    enum DbgState {
205        // no buffer dequeued, don't know anything about the next frame
206        DBG_STATE_IDLE,
207        // output buffer dequeued, framebuffer source not yet known
208        DBG_STATE_BEGUN,
209        // output buffer dequeued, framebuffer source known but not provided
210        // to GLES yet.
211        DBG_STATE_PREPARED,
212        // GLES driver has a buffer dequeued
213        DBG_STATE_GLES,
214        // GLES driver has queued the buffer, we haven't sent it to HWC yet
215        DBG_STATE_GLES_DONE,
216        // HWC has the buffer for this frame
217        DBG_STATE_HWC,
218    };
219    DbgState mDbgState;
220    CompositionType mDbgLastCompositionType;
221
222    const char* dbgStateStr() const;
223    static const char* dbgSourceStr(Source s);
224};
225
226// ---------------------------------------------------------------------------
227} // namespace android
228// ---------------------------------------------------------------------------
229
230#endif // ANDROID_SF_VIRTUAL_DISPLAY_SURFACE_H
231
232