Hi,
Thanks for your comments and sorry for the delay. I was very busy.
In order to fix the memory leak with Scenes, I think it would make sense to
make it happen in the _set_scene method of the director. As you explained,
this is the contract which the director enforces.
Regarding the on_enter method called twice, I was thinking that it might be
useful to people to know when the Transition Scene is completed. Of course,
as you suggested, we can always check if the director scene is a
TransitionScene. But to me, this feels sort of hacky. I was thinking about
other solutions, but I couldn't find anything really great. So I guess what
you suggested is the cleaner way. I'll still give some of my ideas, just in
case ...
One idea was to register an event for TransitionScenes that they would
broadcast when they finish the transition. But Layers interested to know
when their Scene are finished doing the transition need to push a handler
function for that event, which means that the Layer needs to know about the
TransitionScene, which is probably not a good idea.
Another idea was to implement another method to all cocosnodes which would
be called by a TransitionScene when the transition is finished. So let's
say that all cocosnodes had a on_transition_finished method. The Transition
Scene, in its finished method, would call dst.on_transition_finished(). And
obviously the default implementation is just to pass the message down to
the cocosnode children.
def on_transition_finished(self):
for c in self.get_children():
c.on_transition_finished()
So a CocosNode interested in this, could overload this method to do
something appropriately.
But this adds another method to CocosNodes which is only used by
SceneTransitions. So again, not something optimal.
As we're talking about the director, and changing scenes, there is one more
thing I wanted to address. Say we are in a scene and we *push* a new scene.
So the old scene is placed on the stack. Say from this new scene, instead
of poping it, we want to replace it with another scene. Currently this
would leave the old scene still on the stack, which might be what we want,
but maybe not. Maybe we just wanted to get rid of all this stack of scenes
and transition to a brand new scene with a clean stack.
The question is: what is the contract with the director when we change
scene, regarding the stack? I could imagine a keyword argument to
director.replace which would allow the user to wipe out any scenes from the
stack. Something like def replace(self, scene, clean_stack=False)
I will open a new issue on Github for the memory leak. And I'll wait for
your comments regarding the replace method.
Daniel.
Le samedi 10 octobre 2015 10:25:28 UTC+2, Daniel Gillet a écrit :
>
> Hello,
>
> I see some problems with the Scenes transitions. First here is what I'm
> trying to achieve. Imagine a Layer (let's call is static) in a scene. You
> can transition to another scene with another layer (let's call it action).
> This action layer has some actions that should be run when the layer comes
> into play.
>
> So I thought I would launch my action in the `on_enter` method. But with
> the scenes.transitions, it turns out that when creating the scene for the
> transition, the action layer gets its `on_enter` method called. So it
> starts doing its thing while the scenes are transitioning. When the
> transition is done, the director replace the transition scene with the new
> scene containing our action layer. So its `on_enter` gets called again!
>
> Here is a quick demo. You can go from scene 1 to 2 with or without
> transition. Notice that without transition the label jumps twice while
> shaking a bit. If we use a transition, it appears while already jumping and
> jumps more than twice (because of the second call to `on_enter`).
>
> See code here: https://gist.github.com/dangillet/cbd23d5ec4162e960eff
>
> Also I think there is a memory leak! When the transition is completed, if
> you look at the new scene (containing the action layer), you will notice
> that it still has a parent (a scene) which has also a parent (the
> FadeTransition scene) ! Indeed, when the transition finished in
> cocos/director.py we call `director.replace(dst)` but we never delete the
> `self.parent` attribute.
>
> Dan.
>
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