`NativeWindow` is a local platform window of OpenHarmony. It provides APIs for you to create a native window from `Surface`, create a native window buffer from `SurfaceBuffer`, and request and flush a buffer.
**NativeWindow** is a local platform-based window of OpenHarmony that represents the producer of a graphics queue. It provides APIs for you to create a native window from **Surface**, create a native window buffer from **SurfaceBuffer**, and request and flush a buffer.
The following scenarios are common for native window development:
*Drawing content using native C++ code and displaying the content on the screen
* Requesting and flushing a buffer when adapting to EGL `eglswapbuffer`
*Request a graphics buffer by using the NAPI provided by **NativeWindow**, write the produced graphics content to the buffer, and flush the buffer to the graphics queue.
* Request and flush a buffer when adapting to the **eglswapbuffer** interface at the EGL.
## Available APIs
| API| Description|
| -------- | -------- |
| OH_NativeWindow_CreateNativeWindowFromSurface (void \*pSurface) | Creates a `NativeWindow` instance. A new `NativeWindow` instance is created each time this function is called.|
| OH_NativeWindow_DestroyNativeWindow (struct NativeWindow \*window) | Decreases the reference count of a `NativeWindow` instance by 1 and, when the reference count reaches 0, destroys the instance.|
| OH_NativeWindow_CreateNativeWindowBufferFromSurfaceBuffer (void \*pSurfaceBuffer) | Creates a `NativeWindowBuffer` instance. A new `NativeWindowBuffer` instance is created each time this function is called.|
| OH_NativeWindow_DestroyNativeWindowBuffer (struct NativeWindowBuffer \*buffer) | Decreases the reference count of a `NativeWindowBuffer` instance by 1 and, when the reference count reaches 0, destroys the instance.|
| OH_NativeWindow_NativeWindowRequestBuffer (struct NativeWindow \*window struct NativeWindowBuffer \*\*buffer, int \*fenceFd) | Requests a `NativeWindowBuffer` through a `NativeWindow` instance for content production.|
| OH_NativeWindow_NativeWindowFlushBuffer (struct NativeWindow \*window, struct NativeWindowBuffer \*buffer, int fenceFd, Region region) | Flushes the `NativeWindowBuffer` filled with the content to the buffer queue through a `NativeWindow` instance for content consumption.|
| OH_NativeWindow_NativeWindowCancelBuffer (struct NativeWindow \*window, struct NativeWindowBuffer \*buffer) | Returns the `NativeWindowBuffer` to the buffer queue through a `NativeWindow` instance, without filling in any content. The `NativeWindowBuffer` can be used for another request.|
| OH_NativeWindow_NativeWindowHandleOpt (struct NativeWindow \*window, int code,...) | Sets or obtains the attributes of a native window, including the width, height, and content format.|
| OH_NativeWindow_GetBufferHandleFromNative (struct NativeWindowBuffer \*buffer) | Obtains the pointer to a `BufferHandle` of a `NativeWindowBuffer` instance.|
| OH_NativeWindow_CreateNativeWindowFromSurface (void \*pSurface) | Creates a **NativeWindow** instance. A new **NativeWindow** instance is created each time this function is called.|
| OH_NativeWindow_DestroyNativeWindow (OHNativeWindow \*window) | Decreases the reference count of a **NativeWindow** instance by 1 and, when the reference count reaches 0, destroys the instance.|
| OH_NativeWindow_CreateNativeWindowBufferFromSurfaceBuffer (void \*pSurfaceBuffer) | Creates a **NativeWindowBuffer** instance. A new **NativeWindowBuffer** instance is created each time this function is called.|
| OH_NativeWindow_DestroyNativeWindowBuffer (OHNativeWindowBuffer \*buffer) | Decreases the reference count of a **NativeWindowBuffer** instance by 1 and, when the reference count reaches 0, destroys the instance.|
| OH_NativeWindow_NativeWindowRequestBuffer (OHNativeWindow \*window, OHNativeWindowBuffer \*\*buffer, int \*fenceFd) | Requests a **NativeWindowBuffer** through a **NativeWindow** instance for content production.|
| OH_NativeWindow_NativeWindowFlushBuffer (OHNativeWindow \*window, OHNativeWindowBuffer \*buffer, int fenceFd, Region region) | Flushes the **NativeWindowBuffer** filled with the content to the buffer queue through a **NativeWindow** instance for content consumption.|
| OH_NativeWindow_NativeWindowAbortBuffer (OHNativeWindow \*window, OHNativeWindowBuffer \*buffer) | Returns the **NativeWindowBuffer** to the buffer queue through a **NativeWindow** instance, without filling in any content. The **NativeWindowBuffer** can be used for another request.|
| OH_NativeWindow_NativeWindowHandleOpt (OHNativeWindow \*window, int code,...) | Sets or obtains the attributes of a native window, including the width, height, and content format.|
| OH_NativeWindow_GetBufferHandleFromNative (OHNativeWindowBuffer \*buffer) | Obtains the pointer to a **BufferHandle** of a **NativeWindowBuffer** instance.|
| OH_NativeWindow_NativeObjectReference (void \*obj) | Adds the reference count of a native object.|
| OH_NativeWindow_NativeObjectUnreference (void \*obj) | Decreases the reference count of a native object and, when the reference count reaches 0, destroys this object.|
| OH_NativeWindow_GetNativeObjectMagic (void \*obj) | Obtains the magic ID of a native object.|
| OH_NativeWindow_NativeWindowSetScalingMode (OHNativeWindow \*window, uint32_t sequence, OHScalingMode scalingMode) | Sets the scaling mode of the native window.|
| OH_NativeWindow_NativeWindowSetMetaData(OHNativeWindow \*window, uint32_t sequence, int32_t size, const OHHDRMetaData \*metaData) | Sets the HDR static metadata of the native window.|
| OH_NativeWindow_NativeWindowSetMetaDataSet(OHNativeWindow \*window, uint32_t sequence, OHHDRMetadataKey key, int32_t size, const uint8_t \*metaData) | Sets the HDR static metadata set of the native window.|
| OH_NativeWindow_NativeWindowSetTunnelHandle(OHNativeWindow \*window, const OHExtDataHandle \*handle) | Sets the tunnel handle to the native window.|
## How to Develop
The following steps describe how to use `OH_NativeXComponent` in OpenHarmony to draw content using native C++ code and display the content on the screen.
1. Define an `XComponent` of the `texture` type in `index.ets` for content display.
2. Obtain an `OH_NativeXComponent` instance (named `nativeXComponent` in this example) by calling `napi_get_named_property`, and obtain a `NativeWindow` instance by registering the callback of the `OH_NativeXComponent` instance.
The following describes how to use the NAPI provided by **NativeWindow** to request a graphics buffer, write the produced graphics content to the buffer, and flush the buffer to the graphics queue.
1. Obtain a **NativeWindow** instance. For example, use **Surface** to create a **NativeWindow** instance.
```c++
// Define a NAPI instance.
napi_value exportInstance = nullptr;
// Define an OH_NativeXComponent instance.
OH_NativeXComponent *nativeXComponent = nullptr;
// Use the OH_NATIVE_XCOMPONENT_OBJ export instance.
3. Define the callback `OnSurfaceCreated`. During the creation of a `Surface`, the callback is used to initialize the rendering environment, for example, the `Skia` rendering environment, and write the content to be displayed to `NativeWindow`.
2. Set the attributes of a native window buffer by using **OH_NativeWindow_NativeWindowHandleOpt**.
// After the write operation is complete, flush the buffer by using OH_NativeWindow_NativeWindowFlushBuffer so that the data is displayed on the screen.
