html2canvas captures everything except the content of an inner canvas

Question

I've got a map rendered by means of leaflet.

I need to make a screenshot of that map by using html2canvas.

To make use of html2canvas, I need to provide a DOM element to capture (elementToCapture) and an optional configuration (html2canvasConfiguration).

var html2canvasConfiguration = {
    useCORS: true,
    width: map._size.x,
    height: map._size.y,
    backgroundColor: null,
    logging: true,
    imageTimeout: 0
};

var elementToCapture = map._container.getElementsByClassName('leaflet-pane leaflet-map-pane')[0];
html2canvas(elementToCapture, html2canvasConfiguration).then(function (canvas) {
    var link = document.createElement('a');
    link.download = 'test.png';
    link.href = canvas.toDataURL();
    link.click();
    link.remove();
})

I extract an element by the leaflet-pane leaflet-map-pane class, which basically represents the whole map including controls (zoom in/out buttons, scale, etc), custom markers, tooltips, overlays, popups.

The entire DOM looks like

<div class="leaflet-pane leaflet-map-pane">
    <div class="leaflet-pane leaflet-tile-pane">
        <div class="leaflet-gl-layer mapboxgl-map">
            <div class="mapboxgl-canvas-container">
                <canvas class="mapboxgl-canvas leaflet-image-layer leaflet-zoom-animated"></canvas>
            </div>
            <div class="mapboxgl-control-container"></div>
        </div>
    </div>
    <div class="leaflet-pane leaflet-shadow-pane"></div>
    <div class="leaflet-pane leaflet-overlay-pane"></div>
    <div class="leaflet-pane leaflet-marker-pane"></div>
    <div class="leaflet-pane leaflet-tooltip-pane"></div>
    <div class="leaflet-pane leaflet-popup-pane"></div>
<div class="leaflet-control-container"></div>

The problem I've faced is the leaflet-pane leaflet-tile-pane element (particularly the content of the inner canvas) doesn't get captured by html2canvas. To put it simply, I see everything on the map, but I don't see the map itself.

UPDATE 1:

The version I am currently using is 1.0.0-rc.1 (the latest one).

UPDATE 2:

The nature of the canvas is webgl. Might it be the issue? According to this, they do support webgl canvases.

UPDATE 3:

I tried to obtain the canvas programmatically and call toDataURL on it. It resulted in an empty screenshot, even with the preserveDrawingBuffer hack.

UPDATE 4:

Oddly enough, it doesn't capture only certain canvases. I've created a 2d canvas (by adding preferCanvas to map configuration) and it got shown.

Answer 1

Try this, add this to the top of your page, before any other scripts

<script>
HTMLCanvasElement.prototype.getContext = function(origFn) {
  return function(type, attribs) {
    attribs = attribs || {};
    attribs.preserveDrawingBuffer = true;
    return origFn.call(this, type, attribs);
  };
}(HTMLCanvasElement.prototype.getContext);
</script>

Does it help?