Function registerWebGLBackend

tfjs-react-native/src/platform_react_native.ts:192–276

()

}

function registerWebGLBackend() {
  try {
    const PRIORITY = 5;
    tf.registerBackend(
      "rn-webgl",
      async () => {
        const glContext = await GLView.createContextAsync();

        // ExpoGl getBufferSubData is not implemented yet (throws an exception).
        tf.env().set("WEBGL_BUFFER_SUPPORTED", false);

        //
        // Mock extension support for EXT_color_buffer_float and
        // EXT_color_buffer_half_float on the expo-gl context object.
        // In react native we do not have to get a handle to the extension
        // in order to use the functionality of that extension on the device.
        //
        // This code block makes iOS and Android devices pass the extension checks
        // used in core. After those are done core will actually test whether
        // we can render/download float or half float textures.
        //
        // We can remove this block once we upstream checking for these
        // extensions in expo.
        //
        // TODO look into adding support for checking these extensions in expo-gl
        //
        //@ts-ignore
        const getExt = glContext.getExtension.bind(glContext);
        const shimGetExt = (name: string) => {
          if (name === "EXT_color_buffer_float") {
            if (RNPlatform.OS === "ios") {
              // iOS does not support EXT_color_buffer_float
              return null;
            } else {
              return {};
            }
          }

          if (name === "EXT_color_buffer_half_float") {
            return {};
          }
          return getExt(name);
        };

        //
        // Manually make 'read' synchronous. glContext has a defined gl.fenceSync
        // function that throws a "Not implemented yet" exception so core
        // cannot properly detect that it is not supported. We mock
        // implementations of gl.fenceSync and gl.clientWaitSync
        // TODO remove once fenceSync and clientWaitSync is implemented upstream.
        //
        const shimFenceSync = () => {
          return {};
        };
        const shimClientWaitSync = () => glContext.CONDITION_SATISFIED;

        // @ts-ignore
        glContext.getExtension = shimGetExt.bind(glContext);