Add "markerLost" event for THREEx artoolkitControls

[ToufMar]

Do you want to request a feature or report a bug?
feature

What is the current behavior?
I'm working with the Three / Threex version not de A-Frame one.

When I set a addEventListener("markerLost", () => console.log("marker lost") i have nothing whereas with addEventListener("markerFound", () => console.log("marker found") the log is displayed.

You can reproduce it on the nft.html example in three.js just add listeners.

 var markerControls = new THREEx.ArMarkerControls(arToolkitContext, camera, {

            type: 'nft',
            descriptorsUrl: 'data/dataNFT/pinball',
            changeMatrixMode: 'cameraTransformMatrix'
        })
        markerControls.addEventListener('markerFound', () => {
            console.log("hey");
        })
        markerControls.addEventListener('markerLost', () => {
            console.log("nope");
        })

If the current behavior is a bug, please provide the steps to reproduce.

Please mention other relevant information such as the browser version, Operating System and Device Name

What is the expected behavior?
addEventListener("markerLost", (event) => //get event);
If this is a feature request, what is motivation or use case for changing the behavior?
I need this feature to display a target on my screen when marker is lost ..
Thx for every things guys, this lib is awesome !!

[kalwalt]

Hi @ToufMar Are you refering only to NFT for this? Probably this happens because NFT has a different listeners in jsartoolkit5 https://github.com/artoolkitx/jsartoolkit5/blob/244b2b23286403e78fa24805b34509dc5a88052f/js/artoolkit.api.js#L267-L314 I will check this.

[kalwalt]

I think you are right in arMarkerControl we have only markerFound event:

https://github.com/AR-js-org/AR.js/blob/master/three.js/src/threex/threex-armarkercontrols.js#L173

[kalwalt]

We could try to add a dispatch event here

AR.js/three.js/src/threex/threex-armarkercontrols-nft-start.js

Lines 356 to 359 in da5ea83

	_this.context.arController.showObject = true;
	} else {
	_this.context.arController.showObject = false;
	}

something like this:

} else {
          _this.context.arController.showObject = false;
          // dispatchEvent
          this.dispatchEvent({ type: 'markerLost' });
     } 

what do you think @nicolocarpignoli ?

[nicolocarpignoli]

@kalwalt absolutely correct. we can add it on #98 if not already done

[kalwalt]

The problem is that if i add markerLost in that manner, it will be dispatced only for NFT. Instead the dispatced event markerFound is dispatched for every markers type (Pattern, Barcode, Multi...) found.

[ThomasRutzer]

@kalwalt Any chance to dispatch this event for all markers? Should it be fired in this code section?

[nicolocarpignoli]

available now on dev branch: #225