Loading background images into the simulator

[psychemedia]

At the moment this is broken - the image files are hard coded by name in templates/studio.js and via a relative path to a ./images directory.

Backgrounds available via the package need to be referenced by an appropriate path/

Some solution also needs to be found for allow users to load in their own background files. Originally this was done via an upload dialogue. Perhaps an alternative solution would be to path a local path name in via the %%sim_magic call that loads the simulator? <- the upload route via the background selection list is fine for now...

[psychemedia]

Alternatively, the code block magic could accept a parameter that specifies the background to be used for that code.

[psychemedia]

• [ ] There's a recent update to ev3devsim master that improves browser generality for background upload here. That may also improve accessibility?

[psychemedia]

We can change the background from py by calling on js via the widget:

roboSim.js_init("""
  document.getElementById("map").value = "Lollipop";
  // Setting value doesn't seem to raise the event that kicks the loader in?
  // So give it an explicit kick...
  var event = new Event('change');
  document.getElementById("map").dispatchEvent(event);
""")

For the magic, decorate with:

 @magic_arguments.argument('--background', '-b', default='', help='Background selection')

and then call eg:

if args.background:
        self.shell.user_ns[args.sim].js_init(f'''
        var bgSelector = document.getElementById("map")
        bgSelector.value = "{args.background}";
        ''')

BUT THIS DOESN"T WORK... the event doesn't fire to reset the image? Even with:

var event = new Event('change');
document.getElementById("map").dispatchEvent(event);

Ah - maybe it does by changing the event tracked from 'inputtochange`.

I can't figure out how to pass in names containing spaces, eg Background image.

[psychemedia]

Re: accessibility: provide support for an optional audible response that says which background is loaded. Maybe also allow a keyboard shortcut that says the name of the loaded background.