native-window-guidelines.md 6.7 KB

Native Window Development

When to Use

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:

  • 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 (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 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.

    sptr<OHOS::Surface> cSurface = Surface::CreateSurfaceAsConsumer();
    sptr<IBufferConsumerListener> listener = new BufferConsumerListenerTest();
    cSurface->RegisterConsumerListener(listener);
    sptr<OHOS::IBufferProducer> producer = cSurface->GetProducer();
    sptr<OHOS::Surface> pSurface = Surface::CreateSurfaceAsProducer(producer);
    OHNativeWindow* nativeWindow = OH_NativeWindow_CreateNativeWindow(&pSurface);
  2. Set the attributes of a native window buffer by using OH_NativeWindow_NativeWindowHandleOpt.

    // Set the read and write scenarios of the native window buffer.
    int code = SET_USAGE;
    int32_t usage = BUFFER_USAGE_CPU_READ | BUFFER_USAGE_CPU_WRITE | BUFFER_USAGE_MEM_DMA;
    int32_t ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, usage);
    // Set the width and height of the native window buffer.
    code = SET_BUFFER_GEOMETRY;
    int32_t width = 0x100;
    int32_t height = 0x100;
    ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, width, height);
    // Set the step of the native window buffer.
    code = SET_STRIDE;
    int32_t stride = 0x8;
    ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, stride);
    // Set the format of the native window buffer.
    code = SET_FORMAT;
    int32_t format = PIXEL_FMT_RGBA_8888;
    ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, format);
  3. Request a native window buffer from the graphics queue.

    struct NativeWindowBuffer* buffer = nullptr;
    int fenceFd;
    // Obtain the NativeWindowBuffer instance by calling OH_NativeWindow_NativeWindowRequestBuffer.
    OH_NativeWindow_NativeWindowRequestBuffer(nativeWindow_, &buffer, &fenceFd);
    // Obtain the buffer handle by calling OH_NativeWindow_GetNativeBufferHandleFromNative.
    BufferHandle* bufferHandle = OH_NativeWindow_GetNativeBufferHandleFromNative(buffer);
  4. Write the produced content to the native window buffer.

    auto image = static_cast<uint8_t *>(buffer->sfbuffer->GetVirAddr());
    static uint32_t value = 0x00;
    value++;
    
    uint32_t *pixel = static_cast<uint32_t *>(image);
    for (uint32_t x = 0; x < width; x++) {
        for (uint32_t y = 0;  y < height; y++) {
            *pixel++ = value;
        }
    }
  5. Flush the native window buffer to the graphics queue.

    // Set the refresh region. If Rect in Region is a null pointer or rectNumber is 0, all contents in the native window buffer are changed.
    Region region{nullptr, 0};
    // Flush the buffer to the consumer through OH_NativeWindow_NativeWindowFlushBuffer, for example, by displaying it on the screen.
    OH_NativeWindow_NativeWindowFlushBuffer(nativeWindow_, buffer, fenceFd, region);
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