Root component for the BaseGame?

[st-pasha]

I've been looking at flame's code, and noticed that there are lots of similarities between BaseGame and BaseComponent: they both have a ComponentSet, facilities to add, remove and rebalance children.

So I was wondering, what if, instead, BaseGame had a single "root" BaseComponent that would serve as the container for all other components? This could have the following potential benefits:

• avoid code repetition between BaseGame and BaseComponent;
• the components in the game scene now form a proper tree, making tree-traversal algorithms easier;
• there won't be a feature mismatch between what's possible with the BaseGame and the BaseComponent. For example, currently one of them has propagateToChildren while the other changePriorities, however, both methods should be applicable to any component tree;
• when BaseGame has a single root, certain features are easier to implement:
  • onGameResize can be handled by removing the current root and replacing it with a new root recreated from scratch to fit the new size;
  • game navigation (similar to Flutter's Navigator) can be accomplished by replacing the current root with a new root that implements the UI for a new page. For example, consider a hero travelling on the world map and deciding to open his/her inventory. If the inventory is full-screen, I could just replace the root WorldComponent with the InventoryComponent, and then switch them back when the inventory is closed. I can even make the WorldComponent run at 1/10th of the normal clock speed while the inventory is open by running world.update(dt/10) in my inventory's update function.

I don't see any downsides with this approach (but obviously my knowledge of the engine is very shallow), and it won't be a breaking change. A new method BaseComponent replaceRoot(BaseComponent) will be added.

What do you guys think?

[spydon]

I think it is a very good idea, we actually discussed it last week in the team. Another feature that will be the result of this is that you can add a game to a game.

[spydon]

Started the work for this in #906 :)