How do I create a new_view inside a component in GPUI?

[ted-marozzi]

To better explain my question I have created a minimum repro of the problem here.

The question is why when I press the button does the counter never increment? I have only ever gotten this to work but hoisting the cx.new_view() all the way to the top level build root view where the code is only run once per new window, but surely we can create new view down the tree without needing to pass them all the way along? If anyone has worked this out it would be greatly appreciated!

[mikayla-maki]

On each frame you're constructing a new Counter, so it never has a chance to increment before it's dropped. Try storing the counter in the Editor :)

[mikayla-maki]

This is a side effect of our choice to base our object life cycles on reference counting. If no one cares about a View or Model, then we might as well recycle that memory as aggressively as we can detect it. But how do can we detect that no one cares about it? We've decided to answer that with 'if no one has a reference to it'. Therefore, it becomes the GPUI application developer's responsibility to make sure there's a valid path of references from the window (or App, for globals) to anything that you want to stick around.

[mikayla-maki]

(Note that there is an exception to this, Elements are allowed to get some sneaky extra state based on their position in the rendered tree, that GPUI will carry from frame to frame as long as they don't move. However, we need a little help to detect when something has moved, which is why we require you to pass an ElementID before using stateful interfaces. We plan on using this to support components that work the way you're looking for, eventually. We just haven't done it yet, and there are some open questions around how to get the state back out of these components.)

[ted-marozzi]

Thanks I think I understand, so the current solutions are that do what I want seem to be:

• Store views, inside of views inside of view, all of the views must be created up front in the creation of the root application view.
• Create a custom stateful element. Looking at the Stateful struct, I couldn't see where the state could actually be stored, is it that any state in the element itself will be persisted?

[mikayla-maki]

For the stateful element, you'll have to implement two traits: Element and IntoElement. Element gives you access to the state in it's request_layout() method, and IntoElement gives you a chance to associate an ID with the element. Fair warning though implementing elements is a very low level API.

[ted-marozzi]

I can't thank you enough! The views inside of view technique is what I needed. I underestimated the composability of this approach as you can wrap most on the complexity up in a constructor function that takes a context and hence its easy to create multiple of the same component.