1 page.title=Graphics architecture 2 @jd:body 3 4 <!-- 5 Copyright 2014 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18 --> 19 <div id="qv-wrapper"> 20 <div id="qv"> 21 <h2>In this document</h2> 22 <ol id="auto-toc"> 23 </ol> 24 </div> 25 </div> 26 27 28 <p><em>What every developer should know about Surface, SurfaceHolder, 29 EGLSurface, SurfaceView, GLSurfaceView, SurfaceTexture, TextureView, 30 SurfaceFlinger, and Vulkan.</em></p> 31 32 <p>This page describes essential elements of the Android system-level graphics 33 architecture and how they are used by the application framework and multimedia 34 system. The focus is on how buffers of graphical data move through the system. 35 If you've ever wondered why SurfaceView and TextureView behave the way they do, 36 or how Surface and EGLSurface interact, you are in the correct place.</p> 37 38 <p>Some familiarity with Android devices and application development is assumed. 39 You don't need detailed knowledge of the app framework and very few API calls 40 are mentioned, but the material doesn't overlap with other public 41 documentation. The goal is to provide details on the significant events 42 involved in rendering a frame for output to help you make informed choices 43 when designing an application. To achieve this, we work from the bottom up, 44 describing how the UI classes work rather than how they can be used.</p> 45 46 <p>This section includes several pages covering everything from background 47 material to HAL details to use cases. It starts with an explanation of Android 48 graphics buffers, describes the composition and display mechanism, then proceeds 49 to the higher-level mechanisms that supply the compositor with data. We 50 recommend reading pages in the order listed below rather than skipping to a 51 topic that sounds interesting.</p> 52 53 <h2 id=low_level>Low-level components</h2> 54 55 <ul> 56 <li><a href="{@docRoot}devices/graphics/arch-bq-gralloc.html">BufferQueue and 57 gralloc</a>. BufferQueue connects something that generates buffers of graphical 58 data (the <em>producer</em>) to something that accepts the data for display or 59 further processing (the <em>consumer</em>). Buffer allocations are performed 60 through the <em>gralloc</em> memory allocator implemented through a 61 vendor-specific HAL interface.</li> 62 63 <li><a href="{@docRoot}devices/graphics/arch-sf-hwc.html">SurfaceFlinger, 64 Hardware Composer, and virtual displays</a>. SurfaceFlinger accepts buffers of 65 data from multiple sources, composites them, and sends them to the display. The 66 Hardware Composer HAL (HWC) determines the most efficient way to composite 67 buffers with the available hardware, and virtual displays make composited output 68 available within the system (recording the screen or sending the screen over a 69 network).</li> 70 71 <li><a href="{@docRoot}devices/graphics/arch-sh.html">Surface, Canvas, and 72 SurfaceHolder</a>. A Surface produces a buffer queue that is often consumed by 73 SurfaceFlinger. When rendering onto a Surface, the result ends up in a buffer 74 that gets shipped to the consumer. Canvas APIs provide a software implementation 75 (with hardware-acceleration support) for drawing directly on a Surface 76 (low-level alternative to OpenGL ES). Anything having to do with a View involves 77 a SurfaceHolder, whose APIs enable getting and setting Surface parameters such 78 as size and format.</li> 79 80 <li><a href="{@docRoot}devices/graphics/arch-egl-opengl.html">EGLSurface and 81 OpenGL ES</a>. OpenGL ES (GLES) defines a graphics-rendering API designed to be 82 combined with EGL, a library that knows how to create and access windows through 83 the operating system (to draw textured polygons, use GLES calls; to put 84 rendering on the screen, use EGL calls). This page also covers ANativeWindow, 85 the C/C++ equivalent of the Java Surface class used to create an EGL window 86 surface from native code.</li> 87 88 <li><a href="{@docRoot}devices/graphics/arch-vulkan.html">Vulkan</a>. Vulkan is 89 a low-overhead, cross-platform API for high-performance 3D graphics. Like OpenGL 90 ES, Vulkan provides tools for creating high-quality, real-time graphics in 91 applications. Vulkan advantages include reductions in CPU overhead and support 92 for the <a href="https://www.khronos.org/spir">SPIR-V Binary Intermediate</a> 93 language.</li> 94 95 </ul> 96 97 <h2 id=high_level>High-level components</h2> 98 99 <ul> 100 <li><a href="{@docRoot}devices/graphics/arch-sv-glsv.html">SurfaceView and 101 GLSurfaceView</a>. SurfaceView combines a Surface and a View. SurfaceView's View 102 components are composited by SurfaceFlinger (and not the app), enabling 103 rendering from a separate thread/process and isolation from app UI rendering. 104 GLSurfaceView provides helper classes to manage EGL contexts, inter-thread 105 communication, and interaction with the Activity lifecycle (but is not required 106 to use GLES).</li> 107 108 <li><a href="{@docRoot}devices/graphics/arch-st.html">SurfaceTexture</a>. 109 SurfaceTexture combines a Surface and GLES texture to create a BufferQueue for 110 which your app is the consumer. When a producer queues a new buffer, it notifies 111 your app, which in turn releases the previously-held buffer, acquires the new 112 buffer from the queue, and makes EGL calls to make the buffer available to GLES 113 as an external texture. Android 7.0 adds support for secure texture video 114 playback enabling GPU post-processing of protected video content.</li> 115 116 <li><a href="{@docRoot}devices/graphics/arch-tv.html">TextureView</a>. 117 TextureView combines a View with a SurfaceTexture. TextureView wraps a 118 SurfaceTexture and takes responsibility for responding to callbacks and 119 acquiring new buffers. When drawing, TextureView uses the contents of the most 120 recently received buffer as its data source, rendering wherever and however the 121 View state indicates it should. View composition is always performed with GLES, 122 meaning updates to contents may cause other View elements to redraw as well.</li> 123 </ul> 124
