Honor measure width specifications

[jaredjj3]

In #211 (comment), I realized that vexml is not honoring measure width specifications correctly.

• Update the system generating procedure to use the measure specified width as a target width instead of a required width.
• Account for <scaling> when calculating how many pixels a <measure> element's width is.

The data that can be used for testing is: Prelude_No._1_BWV_846_in_C_Major.zip

[jaredjj3]

It sounds like this might be an issue in vexflow as described in vexflow/vexflow#13 (comment). I'm going to use this issue to refactor the rendering.Seed stave width calculations and honor the <scaling> specification.

[jaredjj3]

I'm putting this on ice for now. I tried applying <scaling>, but I realized that I need to scale all the symbols as well — not just the widths. I'll reassign myself when I revisit.

[jaredjj3]

musicxml/scaling.ts

import { NamedElement } from '@/util';

const DEFAULT_MILLIMETERS = 7;
const DEFAULT_TENTHS = 40;
const DEFAULT_MILLIMETERS_PER_TENTH = DEFAULT_MILLIMETERS / DEFAULT_TENTHS;

/**
 * Describes the scaling throughout the MusicXML document.
 *
 * See https://www.w3.org/2021/06/musicxml40/musicxml-reference/elements/scaling/
 */
export class Scaling {
  constructor(private element: NamedElement<'scaling'>) {}

  /** Returns the factor to adjust specified measurements by. */
  getScalingFactor(): number {
    const millimeters = this.getMillimeters();
    const tenths = this.getTenths();
    const millimetersPerTenth = millimeters / tenths;
    return millimetersPerTenth / DEFAULT_MILLIMETERS_PER_TENTH;
  }

  /** Returns the millimeters. */
  getMillimeters(): number {
    return this.element.first('millimeters')?.content().withDefault(DEFAULT_MILLIMETERS).float() ?? DEFAULT_MILLIMETERS;
  }

  /** Returns the tenths. */
  getTenths(): number {
    return this.element.first('tenths')?.content().withDefault(DEFAULT_TENTHS).float() ?? DEFAULT_TENTHS;
  }
}