crescendo.js

VexFlow - Copyright (c) Mohit Muthanna 2010.

Description

This file implements the Crescendo object which draws crescendos and decrescendo dynamics markings. A Crescendo is initialized with a duration and formatted as part of a Voice like any other Note type in VexFlow. This object would most likely be formatted in a Voice with TextNotes - which are used to represent other dynamics markings.

import { Vex } from './vex';
import { Note } from './note';
import { TickContext } from './tickcontext';

To enable logging for this class. Set Vex.Flow.Crescendo.DEBUG to true.

function L() { if (Crescendo.DEBUG) Vex.L('Vex.Flow.Crescendo', arguments); }

Private helper to draw the hairpin

function renderHairpin(ctx, params) {
  const begin_x = params.begin_x;
  const end_x = params.end_x;
  const y = params.y;
  const half_height =  params.height / 2;

  ctx.beginPath();

  if (params.reverse) {
    ctx.moveTo(begin_x, y - half_height);
    ctx.lineTo(end_x,  y);
    ctx.lineTo(begin_x, y + half_height);
  } else {
    ctx.moveTo(end_x,  y - half_height);
    ctx.lineTo(begin_x, y);
    ctx.lineTo(end_x,  y + half_height);
  }

  ctx.stroke();
  ctx.closePath();
}

export class Crescendo extends Note {

Initialize the crescendo’s properties

  constructor(note_struct) {
    super(note_struct);

Whether the object is a decrescendo

    this.decrescendo = false;

The staff line to be placed on

    this.line = note_struct.line || 0;

The height at the open end of the cresc/decresc

    this.height = 15;

    Vex.Merge(this.render_options, {

Extensions to the length of the crescendo on either side

      extend_left: 0,
      extend_right: 0,

Vertical shift

      y_shift: 0,
    });
  }

Set the line to center the element on

  setLine(line) { this.line = line; return this; }

Set the full height at the open end

  setHeight(height) { this.height = height; return this; }

Set whether the sign should be a descresendo by passing a bool to decresc

  setDecrescendo(decresc) {
    this.decrescendo = decresc;
    return this;
  }

Preformat the note

  preFormat() { this.preFormatted = true; return this; }

Render the Crescendo object onto the canvas

  draw() {
    if (!this.context) throw new Vex.RERR('NoContext',
      "Can't draw Hairpin without a context.");

    const tick_context = this.getTickContext();
    const next_context = TickContext.getNextContext(tick_context);

    const begin_x = this.getAbsoluteX();
    let end_x;
    if (next_context) {
      end_x = next_context.getX();
    } else {
      end_x = this.stave.x + this.stave.width;
    }

    const y = this.stave.getYForLine(this.line + (-3)) + 1;

    L('Drawing ',  this.decrescendo ? 'decrescendo ' : 'crescendo ',
      this.height, 'x', begin_x - end_x);

    renderHairpin(this.context, {
      begin_x: begin_x - this.render_options.extend_left,
      end_x: end_x + this.render_options.extend_right,
      y: y + this.render_options.y_shift,
      height: this.height,
      reverse: this.decrescendo,
    });
  }
}

crescendo.js

Table of Contents

Description