MarkerManager.setMarkerSvg fails if the cursor exists and has moved from the top level

[rachel-fenichel]

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Description

MarkerManager.setMarkerSvg is implemented as:

  setMarkerSvg(markerSvg: SVGElement | null) {
    if (!markerSvg) {
      this.markerSvg = null;
      return;
    }

    if (this.workspace.getBlockCanvas()) {
      if (this.cursorSvg) {
        this.workspace
          .getBlockCanvas()!
          .insertBefore(markerSvg, this.cursorSvg);
      } else {
        this.workspace.getBlockCanvas()!.appendChild(markerSvg);
      }
    }
  }

If this.cursorSvg and the block canvas both exist, there's a call to blockCanvas.insertBefore(markerSvg, this.cursorSvg).

If the marker is created immediately after the cursor, this call works because the cursor SVG is a direct child of the block canvas. But if the cursor has been moved around or reparented (e.g. by calling MarkerSvg.setParent_, then the operation fails with:

Failed to execute 'insertBefore' on 'Node': 
    The node before which the new node is to be inserted is not a child of this node.

Reproduction steps

I found this by updating the keyboard-experimentation code to dynamically register and unregister the marker instead of creating it once and leaving it around (attempting to address google/blockly-keyboard-experimentation#181).

Stack trace

Screenshots

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Browsers

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