Native Window Development

When to Use

The native window module is a local platform-based window that represents the producer of a graphics queue. It provides APIs for you to request and flush a buffer and configure buffer attributes.

The following scenarios are common for native window development:

• Request a graphics buffer by using the native window API, 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

For details about the APIs, see native_window.

How to Develop

The following describes how to use the native window APIs to request a graphics buffer, write the produced graphics content to the buffer, and flush the buffer to the graphics queue.

Adding Dynamic Link Libraries

Add the following libraries to CMakeLists.txt:

libace_ndk.z.so
libnative_window.so

Including Header Files

#include <ace/xcomponent/native_interface_xcomponent.h>
#include <native_window/external_window.h>

1. Obtain an OHNativeWindow instance.

   You can call the APIs provided by OH_NativeXComponent_Callback to obtain an OHNativeWindow instance. An example code snippet is provided below. For details about how to use the <XComponent>, see XComponent Development.

   1. Add an <XComponent> to the .ets file.

      XComponent({ id: 'xcomponentId', type: 'surface', libraryname: 'entry'})
          .width(360)
          .height(360)
      

   2. Obtain NativeXComponent at the native C++ layer.

      napi_value exportInstance = nullptr;
      // Parse the attribute of the wrapped NativeXComponent pointer.
      napi_get_named_property(env, exports, OH_NATIVE_XCOMPONENT_OBJ, &exportInstance);
      OH_NativeXComponent *nativeXComponent = nullptr;
      // Use the napi_unwrap API to parse the NativeXComponent instance pointer.
      napi_unwrap(env, exportInstance, reinterpret_cast<void**>(&nativeXComponent));
      // Obtain the XComponent ID.
      char idStr[OH_XCOMPONENT_ID_LEN_MAX + 1] = {};
      uint64_t idSize = OH_XCOMPONENT_ID_LEN_MAX + 1;
      OH_NativeXComponent_GetXComponentId(nativeXComponent, idStr, &idSize);
      

   3. Define OH_NativeXComponent_Callback.

      // Define the callback.
      void OnSurfaceCreatedCB(OH_NativeXComponent* component, void* window)
      {
          // Obtain an OHNativeWindow instance.
          OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
          // ...
      }
      void OnSurfaceChangedCB(OH_NativeXComponent* component, void* window)
      {
          // Obtain an OHNativeWindow instance.
          OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
          // ...
      }
      void OnSurfaceDestroyedCB(OH_NativeXComponent* component, void* window)
      {
          // Obtain an OHNativeWindow instance.
          OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
          // ...
      }
      void DispatchTouchEventCB(OH_NativeXComponent* component, void* window)
      {
          // Obtain an OHNativeWindow instance.
          OHNativeWindow* nativeWindow = static_cast<OHNativeWindow*>(window);
          // ...
      }
      

      // Initialize OH_NativeXComponent_Callback.
      OH_NativeXComponent_Callback callback;
      callback.OnSurfaceCreated = OnSurfaceCreatedCB;
      callback.OnSurfaceChanged = OnSurfaceChangedCB;
      callback.OnSurfaceDestroyed = OnSurfaceDestroyedCB;
      callback.DispatchTouchEvent = DispatchTouchEventCB;
      

   4. Register OH_NativeXComponent_Callback with NativeXComponent.

      // Register the callback.
      OH_NativeXComponent_RegisterCallback(nativeXComponent, &callback);
      

2. Set the attributes of an OHNativeWindowBuffer by using OH_NativeWindow_NativeWindowHandleOpt.

   // Set the width and height of the OHNativeWindowBuffer.
   int32_t code = SET_BUFFER_GEOMETRY;
   int32_t width = 0x100;
   int32_t height = 0x100;
   // The nativeWindow instance is obtained from the callback in the previous step.
   int32_t ret = OH_NativeWindow_NativeWindowHandleOpt(nativeWindow, code, width, height);
   

3. Request an OHNativeWindowBuffer from the graphics queue.

   OHNativeWindowBuffer* buffer = nullptr;
   int fenceFd;
   // Obtain the OHNativeWindowBuffer instance by calling OH_NativeWindow_NativeWindowRequestBuffer.
   OH_NativeWindow_NativeWindowRequestBuffer(nativeWindow, &buffer, &fenceFd);
   // Obtain the buffer handle by calling OH_NativeWindow_GetBufferHandleFromNative.
   BufferHandle* bufferHandle = OH_NativeWindow_GetBufferHandleFromNative(buffer);
   

4. Map memory.

   #include <sys/mman.h>
   
   // Use mmap() to map the shared memory allocated to the buffer handle to the user space. Image data can be written to the buffer handle by using the obtained virtual address.
   // bufferHandle->virAddr indicates the start address of the buffer handle in the shared memory, and bufferHandle->size indicates the memory usage of the buffer handle in the shared memory.
   void* mappedAddr = mmap(bufferHandle->virAddr, bufferHandle->size, PROT_READ | PROT_WRITE, MAP_SHARED, bufferHandle->fd, 0);
   if (mappedAddr == MAP_FAILED) {
       // mmap failed
   }
   

5. Write the produced content to the OHNativeWindowBuffer.

   static uint32_t value = 0x00;
   value++;
   uint32_t *pixel = static_cast<uint32_t *>(mappedAddr); // Use the address obtained by mmap() to access the memory.
   for (uint32_t x = 0; x < width; x++) {
       for (uint32_t y = 0;  y < height; y++) {
           *pixel++ = value;
       }
   }
   

6. Flush the OHNativeWindowBuffer to the graphics queue.

   // Set the refresh region. If Rect in Region is a null pointer or rectNumber is 0, all contents in the OHNativeWindowBuffer 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);
   

7. Unmap memory.

   // Unmap the memory when the memory is no longer required.
   int result = munmap(mappedAddr, bufferHandle->size);
   if (result == -1) {
       // munmap failed
   }