Pixi Spine runtime error

[HappinessSam]

I'm trying to use some spine animations in a large Pixi application at work. It's mostly working but I'm getting intermittent runtime errors coming from the Spine objects.

This error is:Uncaught TypeError: Cannot read property 'transform' of null
    at Spine.e.updateTransform (pixi.min.js:formatted:4401)
    at Spine.autoUpdateTransform (Spine.ts:479)
    at e.updateTransform (pixi.min.js:formatted:4405)
    at e.updateTransform (pixi.min.js:formatted:4405)
    at GameScene.e.updateTransform (pixi.min.js:formatted:4405)
    at e.render (pixi.min.js:formatted:8605)
    at Function.ScenesManager.loop (ScenesManager.ts:273)
    at t.emit (pixi.min.js:formatted:13126)
    at t.update (pixi.min.js:formatted:13068)
    at _tick (pixi.min.js:formatted:12988)

The error is coming from PIXI.Container, line 323 because this.parent is null. This is a bit bonkers because this is only being called because the spine object is in the children list of the scene being rendered.

this.transform.updateTransform(this.parent.transform);

I dug in a tried to isolate the problem and found that somewhere in the Spine update function the parent was being set to null. In Chrome debugger I put in some conditional breakpoints for

dt>0 && this.parent==null

and found that the culprit was line 184

this.state.apply(this.skeleton);

Before this line the breakpoint doesn't trigger, after it it does, with this.parent being null.

I had a read through AnimationState.apply and I can't for the life of me see anything that would be setting the Spine parent state. So my question is can anybody else see anything in there that might be creating this effect?

I should say that the application does a bunch of complicated pooling of symbols, so the Spine object might be getting removed and sent back to the pool then re-added frequently. But my understanding was that since JS is mostly single threaded if this.parent exists on line183 but not 185 something between there must be setting it to null.

I'm not extending or doing anything else to the Spine object. Unfortunately I can't give out any coded to show the context. I'd be really grateful if anybody has any suggestions or input.

[ivan.popelyshev]

Heh, nice one. We have to add guart in auroUpdateTransform - if object was removed after update(0) , dont do updateTransform. Better if you created an issue in pixi-spine repo for that, but here is fine too.

https://github.com/pixijs/pixi-spine/blob/master/src/Spine.ts#L469

PIXI.spine.prototype.autoUpdateTransform = function() {... if (!this.parent) return; ... }

However there will be side effects - neighbour updateTransform() wouldnt be called because that all exists in a loop inside updateTransform of parent. 

Better solution is to switch all autoUpdates (Spine.globalAutoUpdate=false or autoUpdate of every instance), and manually call update() from your game loop. autoUpdateTransform is a great hack, it exists because pixi doesnt have animation loop.

[HappinessSam]

Thanks! That's great info. I think I will look into manually call update, as that looks safer.

[ivan.popelyshev]

Yep, that's recommended action. I hope we'll add animation loop in v5 and it'll be easier.

[HappinessSam]

This has worked fine and touch wood is working perfectly now.

I was also getting an occasional flickering issue which has cleared up after setting the spine's autoupdate to false and updating manually - maybe this apporach would fix https://github.com/pixijs/pixi.js/issues/4117 too.

[ivan.popelyshev]

Good. Now only if that guy gives me complete fiddle and not scraps...