Linear Layout Performance

[MinusGix]

This is an issue relating to poor performance that occurs when having certain layout setups. Not entirely sure that this is a result of linear layout but it is a common denominator, and so the title of the issue should be changed if a different cause is more accurate.

Problem description

Code Example: https://gist.github.com/MinusGix/64c3fedd3a71f45bbd7eef906d8d26fe
This is a very stripped down version of a chat application I'm writing, the example just adding lorem ipsum text 45 times.
Running this with release mode (cargo run --release) results in barely usable delay when scrolling and when simply typing in the textarea.

Removing the TextArea (or replacing it with a TextView with some text) leads to no delay (while still keeping the vertical LinearLayout).
Replacing the TextArea with an EditView leads to the same delay.

Removing the user and LinearLayout in the add_message function (resulting in just doing chat_area.add_child(TextView::new(text)); leads to no delay, but keeping the LinearLayout and removing the user so there is only the text within the horizontal linear layout leads to the delays.

Environment

• Operating system: Manjaro (Arch Linux) using i3.
• Backend used: ncurses 6.2
• Current locale:

  LANG=en_US.UTF-8
  LC_CTYPE="en_US.UTF-8"
  LC_NUMERIC=en_US.UTF-8
  LC_TIME=en_US.UTF-8
  LC_COLLATE="en_US.UTF-8"
  LC_MONETARY=en_US.UTF-8
  LC_MESSAGES="en_US.UTF-8"
  LC_PAPER=en_US.UTF-8
  LC_NAME=en_US.UTF-8
  LC_ADDRESS=en_US.UTF-8
  LC_TELEPHONE=en_US.UTF-8
  LC_MEASUREMENT=en_US.UTF-8
  LC_IDENTIFICATION=en_US.UTF-8
  LC_ALL=

• Cursive version: Crates.io 0.15.0 and latest git version (on main branch)
• Terminals: VSCode integrated terminal, termite, xterm

Note

Not entirely sure as to why this occurs. I'd presume its doing expensive relayouting of the large amount of text when it is unneeded, but I do not know the code base that well.
If you have suggestions for alternate ways of structuring it, I am open to those, but this seemed like the simplest way of getting the format that I desired.

[gyscos]

Hi, and thanks for the report!

The LinearLayout code is definitely a bit messy, especially if we want to play nice with the child views cache; will take a look as soon as I have some time.