Review ui::App for its use of &str/String

[jczuchnowski]

No description provided.

[mtsokol]

Just started learning so I might be all wrong

In app.rs:

I've started looking at the code and I think that e.g. in main event loop for FetcherResponse::FiberDump event to pub fn replace_fiber_dump we could pass &Vec<T> or even just slice &[T](according to reddit comment) as we don't mutate those Fiber structs but only traverse it for creating tree and retrieving label & dump strings. [EDIT] Right now I think that in this case it doesn't matter as it's the only thing happening to those Vectors.

And the same for tree_list_widget and list_tree_nodes for passing references without ownership as format! accepts &str so we don't need to pass an owned variant.
(I see that in this snippet we end up creating number of copies, like for fib_labels)
Then we don't need to instantiate UIFibers with label and dump copies which are then retrieved in the next lines.
At the end append method for Vec accepts a reference which gets emptied there so it think whole replacing fiber dump could be done without copying label and dump strings with clone() and to_owned().

As I understand we use String if we plan to append/change ownership it and for immutable content access we should only pass &str and slices &[T] (although slice can be mut).
WDYT? I might got it wrong completely.