lib-font/src/opentype/tables/simple/variation/fvar.js

A JS based OpenType font inspector

import { SimpleTable } from "../../simple-table.js";
import lazy from "../../../../lazy.js";

/**
 * The OpenType `fvar` table.
 *
 * See https://docs.microsoft.com/en-us/typography/opentype/spec/fvar
 */
class fvar extends SimpleTable {
  constructor(dict, dataview) {
    const { p } = super(dict, dataview);

    this.majorVersion = p.uint16;
    this.minorVersion = p.uint16;
    this.axesArrayOffset = p.Offset16;
    p.uint16;
    this.axisCount = p.uint16;
    this.axisSize = p.uint16;
    this.instanceCount = p.uint16;
    this.instanceSize = p.uint16;

    const axisStart = this.tableStart + this.axesArrayOffset;
    lazy(this, `axes`, () => {
      p.currentPosition = axisStart;
      return [...new Array(this.axisCount)].map(
        (_) => new VariationAxisRecord(p)
      );
    });

    const instanceStart = axisStart + this.axisCount * this.axisSize;
    lazy(this, `instances`, () => {
      let instances = [];
      for (let i = 0; i < this.instanceCount; i++) {
        p.currentPosition = instanceStart + i * this.instanceSize;
        instances.push(
          new InstanceRecord(p, this.axisCount, this.instanceSize)
        );
      }
      return instances;
    });
  }

  getSupportedAxes() {
    return this.axes.map((a) => a.tag);
  }

  getAxis(name) {
    return this.axes.find((a) => a.tag === name);
  }
}

class VariationAxisRecord {
  constructor(p) {
    this.tag = p.tag;
    this.minValue = p.fixed;
    this.defaultValue = p.fixed;
    this.maxValue = p.fixed;
    this.flags = p.flags(16);
    this.axisNameID = p.uint16;
  }
}

class InstanceRecord {
  constructor(p, axisCount, size) {
    let start = p.currentPosition;
    this.subfamilyNameID = p.uint16;
    p.uint16;
    this.coordinates = [...new Array(axisCount)].map((_) => p.fixed);
    if (p.currentPosition - start < size) {
      this.postScriptNameID = p.uint16;
    }
  }
}

export { fvar };