NativeWindow是本地平台化窗口，表示图形队列的生产者端，主要用于需要高效图形数据处理的场景。当开发者开发视频播放、相机预览、游戏渲染等图形密集型应用时，需要在图形缓冲区中高效地写入和提交图形数据。此时，开发者可以通过NativeWindow接口进行申请和提交Buffer，配置Buffer属性信息。

针对NativeWindow，常见的开发场景如下：

通过NativeWindow提供的Native API接口申请图形Buffer，并将生成的图形内容写入图形Buffer，最终提交Buffer到图形队列。
在适配EGL层的eglswapbuffer接口时，进行申请和提交Buffer。

接口说明

接口名	描述
OH_NativeWindow_NativeWindowRequestBuffer (OHNativeWindow window, OHNativeWindowBuffer buffer, int fenceFd)	通过OHNativeWindow对象申请一块OHNativeWindowBuffer，用以内容生产。
OH_NativeWindow_NativeWindowFlushBuffer (OHNativeWindow window, OHNativeWindowBuffer buffer, int fenceFd, Region region)	通过OHNativeWindow将生产好内容的OHNativeWindowBuffer放回到Buffer队列中，用以内容消费。
OH_NativeWindow_NativeWindowHandleOpt (OHNativeWindow *window, int code,...)	设置/获取OHNativeWindow的属性，包括设置/获取宽高、内容格式等。

详细的接口说明请参考NativeWindow。

开发步骤

以下步骤描述了如何使用NativeWindow提供的Native API接口申请图形Buffer，写入图形内容，并提交Buffer到图形队列。

添加动态链接库

CMakeLists.txt中添加以下lib。

libace_ndk.z.so
libnative_window.so

头文件

#include <sys/poll.h>
#include <sys/mman.h>
#include <unistd.h>
#include <ace/xcomponent/native_interface_xcomponent.h>
#include <native_window/external_window.h>

获取OHNativeWindow实例。

可通过OH_NativeXComponent_Callback接口获取OHNativeWindow。代码示例如下。关于XComponent模块的使用方法，详见XComponent开发指导。

在xxx.ets中添加一个XComponent组件。

XComponent({ id: 'xcomponentId', type: 'texture', libraryname: 'nativerender' })
  .margin({ bottom: 26 })
  .onLoad((nativeWindowContext) => {
    this.nativeWindowContext = nativeWindowContext as NativeWindowContext;
  })

在 native c++ 层获取 NativeXComponent。

napi_value exportInstance = nullptr;
OH_NativeXComponent *nativeXComponent = nullptr;
int32_t ret;
char idStr[OH_XCOMPONENT_ID_LEN_MAX + 1] = {};
uint64_t idSize = OH_XCOMPONENT_ID_LEN_MAX + 1;

status = napi_get_named_property(env, exports, OH_NATIVE_XCOMPONENT_OBJ, &exportInstance);
if (status != napi_ok) {
    return false;
}

status = napi_unwrap(env, exportInstance, reinterpret_cast<void**>(&nativeXComponent));
if (status != napi_ok) {
    return false;
}

ret = OH_NativeXComponent_GetXComponentId(nativeXComponent, idStr, &idSize);
if (ret != OH_NATIVEXCOMPONENT_RESULT_SUCCESS) {
    return false;
}

定义 OH_NativeXComponent_Callback。

void OnSurfaceCreatedCB(OH_NativeXComponent* component, void* window)
{
    // ...
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}

void OnSurfaceChangedCB(OH_NativeXComponent* component, void* window)
{
    // ...
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}

void OnSurfaceDestroyedCB(OH_NativeXComponent* component, void* window)
{
    // ...
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
    // ...
}

void DispatchTouchEventCB(OH_NativeXComponent* component, void* window)
{
    // ...
    OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
}
// ...
callback_.OnSurfaceCreated = OnSurfaceCreatedCB;
callback_.OnSurfaceChanged = OnSurfaceChangedCB;
callback_.OnSurfaceDestroyed = OnSurfaceDestroyedCB;
callback_.DispatchTouchEvent = DispatchTouchEventCB;

将OH_NativeXComponent_Callback 注册给 NativeXComponent。

OH_NativeXComponent_RegisterCallback(nativeXComponent, &callback_);

设置OHNativeWindow的属性。使用OH_NativeWindow_NativeWindowHandleOpt设置OHNativeWindowBuffer的属性（默认携带NATIVEBUFFER_USAGE_CPU_READ usage参数，如果不使用CPU读写数据，建议去除NATIVEBUFFER_USAGE_CPU_READ usage参数，具体可见关闭CPU访问窗口缓冲区数据）。
```
int code = SET_BUFFER_GEOMETRY;
int32_t bufferHeight = static_cast<int32_t>(height_ / 4);
int32_t bufferWidth = static_cast<int32_t>(width_ / 2);
OH_NativeWindow_NativeWindowHandleOpt(nativeWindow_, code, bufferWidth, bufferHeight);
```

从图形队列申请OHNativeWindowBuffer。

int releaseFenceFd = -1;
OHNativeWindowBuffer *nativeWindowBuffer = nullptr;
ret = OH_NativeWindow_NativeWindowRequestBuffer(nativeWindow, &nativeWindowBuffer, &releaseFenceFd);
if (ret != 0 || nativeWindowBuffer == nullptr) {
    return;
}
BufferHandle *bufferHandle = OH_NativeWindow_GetBufferHandleFromNative(nativeWindowBuffer);

内存映射mmap。

void *mappedAddr =
    mmap(bufferHandle->virAddr, bufferHandle->size, PROT_READ | PROT_WRITE, MAP_SHARED, bufferHandle->fd, 0);

将生产的内容写入OHNativeWindowBuffer，在这之前需要等待releaseFenceFd可用（注意releaseFenceFd不等于-1才需要调用poll）。如果没有等待releaseFenceFd事件的数据可用（POLLIN），则可能造成花屏、裂屏、HEBC（High Efficiency Bandwidth Compression，高效带宽压缩） fault等问题。releaseFenceFd是消费者进程创建的一个文件句柄，代表消费者消费buffer完毕，buffer可读，生产者可以开始填充buffer内容。

int retCode = -1;
uint32_t timeout = 3000;
if (releaseFenceFd != -1) {
    struct pollfd pollfds = {0};
    pollfds.fd = releaseFenceFd;
    pollfds.events = POLLIN;
    do {
        retCode = poll(&pollfds, 1, timeout);
    } while (retCode == -1 && (errno == EINTR || errno == EAGAIN));
    close(releaseFenceFd);
}
uint32_t *pixel = static_cast<uint32_t *>(mappedAddr);
uint32_t value = flag_ ? 0xfff0000f : 0xff00ffff;
for (uint64_t x = 0; x < bufferHandle->width; x++) {
    for (uint64_t y = 0; y < bufferHandle->height; y++) {
        *pixel++ = value;
    }
}

提交OHNativeWindowBuffer到图形队列。请注意OH_NativeWindow_NativeWindowFlushBuffer接口的acquireFenceFd不可以和OH_NativeWindow_NativeWindowRequestBuffer接口获取的releaseFenceFd相同，acquireFenceFd可传入默认值-1。acquireFenceFd是生产者需要传入的文件句柄，消费者获取到buffer后可根据生产者传入的acquireFenceFd决定何时去渲染并上屏buffer内容。
```
struct Region region = {0};
int acquireFenceFd = -1;
ret = OH_NativeWindow_NativeWindowFlushBuffer(nativeWindow, nativeWindowBuffer, acquireFenceFd, region);
if (ret != NATIVE_ERROR_OK) {
    LOGE("flush failed");
    (void)OH_NativeWindow_NativeWindowAbortBuffer(nativeWindow, nativeWindowBuffer);
    return;
}
```

使用munmap取消内存映射。

if (munmap(mappedAddr, bufferHandle->size) < 0) {
    OH_NativeWindow_DestroyNativeWindow(nativeWindow);
    LOGE("munmap failed");
    return;
}

目录

NativeWindow开发指导 (C/C++)

场景介绍

接口说明

开发步骤