3b748a44c6
When the Android runtime starts, the system preloads a series of assets in the Zygote process. These assets are shared across all processes. Unfortunately, each one of these assets is later uploaded in its own OpenGL texture, once per process. This wastes memory and generates unnecessary OpenGL state changes. This CL introduces an asset server that provides an atlas to all processes. Note: bitmaps used by skia shaders are *not* sampled from the atlas. It's an uncommon use case and would require extra texture transforms in the GL shaders. WHAT IS THE ASSETS ATLAS The "assets atlas" is a single, shareable graphic buffer that contains all the system's preloaded bitmap drawables (this includes 9-patches.) The atlas is made of two distinct objects: the graphic buffer that contains the actual pixels and the map which indicates where each preloaded bitmap can be found in the atlas (essentially a pair of x and y coordinates.) HOW IS THE ASSETS ATLAS GENERATED Because we need to support a wide variety of devices and because it is easy to change the list of preloaded drawables, the atlas is generated at runtime, during the startup phase of the system process. There are several steps that lead to the atlas generation: 1. If the device is booting for the first time, or if the device was updated, we need to find the best atlas configuration. To do so, the atlas service tries a number of width, height and algorithm variations that allows us to pack as many assets as possible while using as little memory as possible. Once a best configuration is found, it gets written to disk in /data/system/framework_atlas 2. Given a best configuration (algorithm variant, dimensions and number of bitmaps that can be packed in the atlas), the atlas service packs all the preloaded bitmaps into a single graphic buffer object. 3. The packing is done using Skia in a temporary native bitmap. The Skia bitmap is then copied into the graphic buffer using OpenGL ES to benefit from texture swizzling. HOW PROCESSES USE THE ATLAS Whenever a process' hardware renderer initializes its EGL context, it queries the atlas service for the graphic buffer and the map. It is important to remember that both the context and the map will be valid for the lifetime of the hardware renderer (if the system process goes down, all apps get killed as well.) Every time the hardware renderer needs to render a bitmap, it first checks whether the bitmap can be found in the assets atlas. When the bitmap is part of the atlas, texture coordinates are remapped appropriately before rendering. Change-Id: I8eaecf53e7f6a33d90da3d0047c5ceec89ea3af0
78 lines
2.3 KiB
C++
78 lines
2.3 KiB
C++
/*
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* Copyright (C) 2010 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_HWUI_PATCH_H
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#define ANDROID_HWUI_PATCH_H
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#include <sys/types.h>
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#include <GLES2/gl2.h>
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#include <utils/Vector.h>
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#include <androidfw/ResourceTypes.h>
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#include "Rect.h"
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#include "UvMapper.h"
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#include "Vertex.h"
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namespace android {
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namespace uirenderer {
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///////////////////////////////////////////////////////////////////////////////
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// 9-patch structures
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///////////////////////////////////////////////////////////////////////////////
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struct Patch {
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Patch();
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~Patch();
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/**
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* Returns the size of this patch's mesh in bytes.
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*/
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uint32_t getSize() const;
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uint32_t verticesCount;
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uint32_t indexCount;
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bool hasEmptyQuads;
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Vector<Rect> quads;
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GLintptr offset;
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GLintptr textureOffset;
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TextureVertex* createMesh(const float bitmapWidth, const float bitmapHeight,
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float left, float top, float right, float bottom,
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const Res_png_9patch* patch);
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TextureVertex* createMesh(const float bitmapWidth, const float bitmapHeight,
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float left, float top, float right, float bottom,
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const UvMapper& mapper, const Res_png_9patch* patch);
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private:
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void generateRow(const int32_t* xDivs, uint32_t xCount, TextureVertex*& vertex,
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float y1, float y2, float v1, float v2, float stretchX, float rescaleX,
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float width, float bitmapWidth, uint32_t& quadCount);
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void generateQuad(TextureVertex*& vertex, float x1, float y1, float x2, float y2,
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float u1, float v1, float u2, float v2, uint32_t& quadCount);
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uint32_t mColorKey;
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UvMapper mUvMapper;
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}; // struct Patch
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}; // namespace uirenderer
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}; // namespace android
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#endif // ANDROID_HWUI_PATCH_H
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