Understanding redoLayout()

[samuelbradshaw]

Some toolkit options only seem to work if they're set before loading data. Is this expected, or is it a bug? If expected, is it documented anywhere which options need to be set before loading?

For example, this correctly sets an expansion, transposition, and page width:

let vrvToolkit;
verovio.module.onRuntimeInitialized = function() {
  vrvToolkit = new verovio.toolkit();
  
  vrvToolkit.setOptions({
    expand: 'expansion1',
    transpose: 'g',
    pageWidth: 500,
  });
  
  vrvToolkit.loadData(score); // Load data after setting options
  vrvToolkit.redoLayout();
  
  const numPages = vrvToolkit.getPageCount();
  container.innerHTML = '';
  for (let p = 1; p <= numPages; p++) {
    const svg = vrvToolkit.renderToSVG(p);
    container.insertAdjacentHTML('beforeend', svg);
  }
};

But this only sets the page width (expand and transpose are ignored):

let vrvToolkit;
verovio.module.onRuntimeInitialized = function() {
  vrvToolkit = new verovio.toolkit();
  vrvToolkit.loadData(score); // Load data before setting options
  
  vrvToolkit.setOptions({
    expand: 'expansion1',
    transpose: 'g',
    pageWidth: 500,
  });
  
  vrvToolkit.redoLayout();
  
  const numPages = vrvToolkit.getPageCount();
  container.innerHTML = '';
  for (let p = 1; p <= numPages; p++) {
    const svg = vrvToolkit.renderToSVG(p);
    container.insertAdjacentHTML('beforeend', svg);
  }
};

[lpugin]

Good question! This is not a bug and it is expected. I thought this was documented but I don't think it actually is, so we need to clarify it.

Basically, a few options transform the data when loading. Most of them are in the selectors option group, such as --transpose. The transposition happens when loading the file, which means that if you want to transpose it again, the file has to be reloaded.

We need to move a few to that option group, such as --expand, which now also transforms the content when loading (see discussion here):
5e19c9a

The branch also rewords the option description from "Element selectors and processing" to "Loading selectors and processing", which I hope will make it clearer. However, we still need to add an explanation in the documentation somewhere else. I'll have a look.