harfbuzzjs/harfbuzz.ts

Minimal version of HarfBuzz for JavaScript use

type Pointer = number;

const HB_MEMORY_MODE_WRITABLE: number = 2;
const HB_SET_VALUE_INVALID: Pointer = -1;

class HarfBuzzExports {
  readonly heapu8: Uint8Array;
  readonly heapu32: Uint32Array;
  readonly heapi32: Int32Array;
  readonly utf8Encoder: TextEncoder;

  //exported HarfBuzz methods
  readonly malloc: (length: number) => Pointer
  readonly free: (ptr: Pointer) => void
  readonly free_ptr: () => Pointer
  readonly hb_blob_create: (data: Pointer, length: number, memoryMode: number, useData: Pointer, destroyFunction: Pointer) => Pointer
  readonly hb_blob_destroy: (ptr: Pointer) => void
  readonly hb_face_create: (blobPtr: Pointer, index: number) => Pointer
  readonly hb_face_get_upem: (facePtr: Pointer) => number
  readonly hb_face_destroy: (ptr: Pointer) => void
  readonly hb_font_create: (facePtr: Pointer) => Pointer
  readonly hb_font_set_scale: (fontPtr: Pointer, xScale: number, yScale: number) => void
  readonly hb_font_destroy: (ptr: Pointer) => void
  readonly hb_face_collect_unicodes: (facePtr: Pointer, setPtr: Pointer) => void
  readonly hb_set_create: () => Pointer
  readonly hb_set_destroy: (setPtr: Pointer) => void
  readonly hb_set_get_population: (setPtr: Pointer) => number
  readonly hb_set_next_many: (
    setPtr: Pointer,
    greaterThanUnicodePtr: Pointer,
    outputU32ArrayPtr: Pointer,
    size: number,
  ) => number
  readonly hb_buffer_create: () => Pointer
  readonly hb_buffer_add_utf8: (bufferPtr: Pointer, stringPtr: Pointer, stringLength: number, itemOffset: number, itemLength: number) => void
  readonly hb_buffer_guess_segment_properties: (bufferPtr: Pointer) => void
  readonly hb_buffer_set_direction: (bufferPtr: Pointer, direction: number) => void
  readonly hb_shape: (fontPtr: Pointer, bufferPtr: Pointer, features: any, numFeatures: number) => void
  readonly hb_buffer_get_length: (bufferPtr: Pointer) => number
  readonly hb_buffer_get_glyph_infos: (bufferPtr: Pointer, length: number) => any
  readonly hb_buffer_get_glyph_positions: (bufferPtr: Pointer, length: number) => any
  readonly hb_buffer_destroy: (bufferPtr: Pointer) => void

  constructor(exports: any) {
    this.heapu8 = new Uint8Array(exports.memory.buffer);
    this.heapu32 = new Uint32Array(exports.memory.buffer);
    this.heapi32 = new Int32Array(exports.memory.buffer);
    this.utf8Encoder = new TextEncoder();

    this.malloc = exports.malloc;
    this.free = exports.free;
    this.free_ptr = exports.free_ptr;
    this.hb_blob_destroy = exports.hb_blob_destroy;
    this.hb_blob_create = exports.hb_blob_create;
    this.hb_face_create = exports.hb_face_create;
    this.hb_face_get_upem = exports.hb_face_get_upem;
    this.hb_face_destroy = exports.hb_face_destroy;
    this.hb_face_collect_unicodes = exports.hb_face_collect_unicodes;
    this.hb_set_create = exports.hb_set_create;
    this.hb_set_destroy = exports.hb_set_destroy;
    this.hb_set_get_population = exports.hb_set_get_population;
    this.hb_set_next_many = exports.hb_set_next_many;
    this.hb_font_create = exports.hb_font_create;
    this.hb_font_set_scale = exports.hb_font_set_scale;
    this.hb_font_destroy = exports.hb_font_destroy;
    this.hb_buffer_create = exports.hb_buffer_create;
    this.hb_buffer_add_utf8 = exports.hb_buffer_add_utf8;
    this.hb_buffer_guess_segment_properties = exports.hb_buffer_guess_segment_properties;
    this.hb_buffer_set_direction = exports.hb_buffer_set_direction;
    this.hb_shape = exports.hb_shape;
    this.hb_buffer_get_length = exports.hb_buffer_get_length;
    this.hb_buffer_get_glyph_infos = exports.hb_buffer_get_glyph_infos;
    this.hb_buffer_get_glyph_positions = exports.hb_buffer_get_glyph_positions;
    this.hb_buffer_destroy = exports.hb_buffer_destroy;
  }

}

let hb: HarfBuzzExports;

class CString {
  readonly ptr: Pointer;
  readonly length: number;

  constructor(text: string) {
    var bytes = hb.utf8Encoder.encode(text);
    this.ptr = hb.malloc(bytes.byteLength);
    hb.heapu8.set(bytes, this.ptr);
    this.length = bytes.byteLength;
  }

  destroy() {
    hb.free(this.ptr);
  }
}

export class HarfBuzzBlob {
  readonly ptr: Pointer;

  constructor(data: Uint8Array) {
    let blobPtr = hb.malloc(data.length);
    hb.heapu8.set(data, blobPtr);
    this.ptr = hb.hb_blob_create(blobPtr, data.byteLength, HB_MEMORY_MODE_WRITABLE, blobPtr, hb.free_ptr());
  }

  destroy() {
    hb.hb_blob_destroy(this.ptr);
  }
}

function typedArrayFromSet<T extends 'u8' | 'u32' | 'i32'>(setPtr: Pointer, arrayType: T) {
  const heap = hb[`heap${arrayType}`];
  const bytesPerElment = heap.BYTES_PER_ELEMENT;
  const setCount = hb.hb_set_get_population(setPtr);
  const arrayPtr = hb.malloc(
    setCount * bytesPerElment,
  );
  const arrayOffset = arrayPtr / bytesPerElment;
  const array = heap.subarray(
    arrayOffset,
    arrayOffset + setCount,
  ) as typeof hb[`heap${T}`];
  heap.set(array, arrayOffset);
  hb.hb_set_next_many(
    setPtr,
    HB_SET_VALUE_INVALID,
    arrayPtr,
    setCount,
  );
  return array;
}

export class HarfBuzzFace {
  readonly ptr: Pointer;

  constructor(blob: HarfBuzzBlob, index: number) {
    this.ptr = hb.hb_face_create(blob.ptr, index);
  }

  getUnitsPerEM() {
    return hb.hb_face_get_upem(this.ptr);
  }

  collectUnicodes() {
    const unicodeSetPtr = hb.hb_set_create();
    hb.hb_face_collect_unicodes(this.ptr, unicodeSetPtr);
    const result = typedArrayFromSet(unicodeSetPtr, 'u32');
    hb.hb_set_destroy(unicodeSetPtr);
    return result;
  }

  destroy() {
    hb.hb_face_destroy(this.ptr);
  }
}

export class HarfBuzzFont {
  readonly ptr: Pointer
  readonly unitsPerEM: number

  constructor(face: HarfBuzzFace) {
    this.ptr = hb.hb_font_create(face.ptr);
    this.unitsPerEM = face.getUnitsPerEM();
  }

  setScale(xScale: number, yScale: number) {
    hb.hb_font_set_scale(this.ptr, xScale, yScale);
  }

  destroy() {
    hb.hb_font_destroy(this.ptr);
  }
}

export type HarfBuzzDirection = "ltr" | "rtl" | "ttb" | "btt"

class GlyphInformation {
  readonly GlyphId: number
  readonly Cluster: number
  readonly XAdvance: number
  readonly YAdvance: number
  readonly XOffset: number
  readonly YOffset: number

  constructor(glyphId: number, cluster: number, xAdvance: number, yAdvance: number, xOffset: number, yOffset: number) {
    this.GlyphId = glyphId;
    this.Cluster = cluster;
    this.XAdvance = xAdvance;
    this.YAdvance = yAdvance;
    this.XOffset = xOffset;
    this.YOffset = yOffset;
  }
}

export class HarfBuzzBuffer {
  readonly ptr: Pointer

  constructor() {
    this.ptr = hb.hb_buffer_create();
  }

  addText(text: string) {
    let str = new CString(text);
    hb.hb_buffer_add_utf8(this.ptr, str.ptr, str.length, 0, str.length);
    str.destroy();
  }

  guessSegmentProperties() {
    hb.hb_buffer_guess_segment_properties(this.ptr);
  }

  setDirection(direction: HarfBuzzDirection) {
    let d = { "ltr": 4, "rtl": 5, "ttb": 6, "btt": 7 }[direction];
    hb.hb_buffer_set_direction(this.ptr, d);
  }

  json() {
    var length = hb.hb_buffer_get_length(this.ptr);
    var result = new Array<GlyphInformation>();
    var infosPtr32 = hb.hb_buffer_get_glyph_infos(this.ptr, 0) / 4;
    var positionsPtr32 = hb.hb_buffer_get_glyph_positions(this.ptr, 0) / 4;
    var infos = hb.heapu32.subarray(infosPtr32, infosPtr32 + 5 * length);
    var positions = hb.heapi32.subarray(positionsPtr32, positionsPtr32 + 5 * length);
    for (var i = 0; i < length; ++i) {
      result.push(new GlyphInformation(
        infos[i * 5 + 0],
        infos[i * 5 + 2],
        positions[i * 5 + 0],
        positions[i * 5 + 1],
        positions[i * 5 + 2],
        positions[i * 5 + 3]));
    }
    return result;
  }

  destroy() {
    hb.hb_buffer_destroy(this.ptr)
  }
}

export function shape(text: string, font: HarfBuzzFont, features: any): Array<GlyphInformation> {
  let buffer = new HarfBuzzBuffer();
  buffer.addText(text);
  buffer.guessSegmentProperties();
  buffer.shape(font, features);
  let result = buffer.json();
  buffer.destroy();
  return result;
}

export function getWidth(text: string, font: HarfBuzzFont, fontSizeInPixel: number, features: any): number {
  let scale = fontSizeInPixel / font.unitsPerEM;
  let shapeResult = shape(text, font, features);
  let totalWidth = shapeResult.map((glyphInformation) => {
    return glyphInformation.XAdvance;
  }).reduce((previous, current, i, arr) => {
    return previous + current;
  }, 0.0);

  return totalWidth * scale;
}

export const harfbuzzFonts = new Map<string, HarfBuzzFont>();

export function loadHarfbuzz(webAssemblyUrl: string): Promise<void> {
  return fetch(webAssemblyUrl).then(response => {
    return response.arrayBuffer();
  }).then(wasm => {
    return WebAssembly.instantiate(wasm);
  }).then(result => {
    //@ts-ignore
    hb = new HarfBuzzExports(result.instance.exports);
  });
}

export function loadAndCacheFont(fontName: string, fontUrl: string): Promise<void> {
  return fetch(fontUrl).then((response) => {
    return response.arrayBuffer().then((blob) => {
      let fontBlob = new Uint8Array(blob);
      let harfbuzzBlob = new HarfBuzzBlob(fontBlob);
      let harfbuzzFace = new HarfBuzzFace(harfbuzzBlob, 0);
      let harfbuzzFont = new HarfBuzzFont(harfbuzzFace);

      harfbuzzFonts.set(fontName, harfbuzzFont);
      harfbuzzFace.destroy();
      harfbuzzBlob.destroy();
    });
  });
}