VirtualDisplaySurface.h revision 851cfe834295224cd64bdd499872b95b19c4de8c 
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 "BufferQueueInterposer.h"
21#include "DisplaySurface.h"
22
23// ---------------------------------------------------------------------------
24namespace android {
25// ---------------------------------------------------------------------------
26
27class HWComposer;
28
29/* This DisplaySurface implementation uses a BufferQueueInterposer to pass
30 * partially- or fully-composited buffers from the OpenGL ES driver to
31 * HWComposer to use as the output buffer for virtual displays. Allowing HWC
32 * to compose into the same buffer that contains GLES results saves bandwidth
33 * compared to having two separate BufferQueues for frames with at least some
34 * GLES composition.
35 *
36 * The alternative would be to have two complete BufferQueues, one from GLES
37 * to HWC and one from HWC to the virtual display sink (e.g. video encoder).
38 * For GLES-only frames, the same bandwidth saving could be achieved if buffers
39 * could be acquired from the GLES->HWC queue and inserted into the HWC->sink
40 * queue. That would be complicated and doesn't help the mixed GLES+HWC case.
41 *
42 * On frames with no GLES composition, the VirtualDisplaySurface dequeues a
43 * buffer directly from the sink IGraphicBufferProducer and passes it to HWC,
44 * bypassing the GLES driver. This is only guaranteed to work if
45 * eglSwapBuffers doesn't immediately dequeue a buffer for the next frame,
46 * since we can't rely on being able to dequeue more than one buffer at a time.
47 *
48 * TODO(jessehall): Add a libgui test that ensures that EGL/GLES do lazy
49 * dequeBuffers; we've wanted to require that for other reasons anyway.
50 */
51class VirtualDisplaySurface : public DisplaySurface {
52public:
53    VirtualDisplaySurface(HWComposer& hwc, int disp,
54            const sp<IGraphicBufferProducer>& sink,
55            const String8& name);
56
57    virtual sp<IGraphicBufferProducer> getIGraphicBufferProducer() const;
58
59    virtual status_t compositionComplete();
60    virtual status_t advanceFrame();
61    virtual void onFrameCommitted();
62    virtual void dump(String8& result) const;
63
64private:
65    virtual ~VirtualDisplaySurface();
66
67    // immutable after construction
68    HWComposer& mHwc;
69    int mDisplayId;
70    sp<BufferQueueInterposer> mSource;
71    String8 mName;
72
73    // mutable, must be synchronized with mMutex
74    Mutex mMutex;
75    sp<GraphicBuffer> mAcquiredBuffer;
76};
77
78// ---------------------------------------------------------------------------
79} // namespace android
80// ---------------------------------------------------------------------------
81
82#endif // ANDROID_SF_VIRTUAL_DISPLAY_SURFACE_H
83
84