Screen that dumps raw bytes for terminal

[mavam]

I've written a TUI that displays structured tabular data. I now need a one-shot rendering opportunity to dump this output anywhere, e.g., to stdout, stderr, file, etc. Where the raw bytes go that make up rendered output is opaque in my API. I can literally just pass bytes downstream.

So what I am looking for is a function that gives me a byte sequence that represents my rendered screen. I would like to offer two options: colored and monochrome. I am not sure where FTXUI internals produce this raw byte sequence before it hits the TTY, but that's where I would hope to get a chance to interpose—optionally enable/disable coloring.

What's the best way to make this happen?

[mavam]

My hope was that ScreenInteractive::ToString simply dumps the screen as a string, so that I can control the "shipping to the terminal" separately. Unfortunately that's not the case. Is there any side-effect free function to print a screen?

[ArthurSonzogni]

Hello @mavam, I think you are describing this function:

std::string ToString(Component& component) {
  auto document = component->render();
  auto screen = Screen::Create(Dimension::Full(), Dimension::Fit(document));
  Render(screen, document);
  return screen.ToString();
}

[mavam]

I think this can work. Two questions:

1. ~I'm getting unfortunately no output when I blindly execute your code suggestion. Then I tried adding a Loop and called RunBlockingOnce(). Then I got the desired output, but it was also rendered to the terminal. So this was not quite the right path. Is there another way to "kick the tires" on the component?

2. Since this is a single snapshot of a (container) component, the focus is on the first child of the component. Because the component changes its style when focused, it is highlighted even though I just want a static view without highlighting. If I understand the FTXUI architecture correctly, the user must be somewhere, so the focus must be somewhere. I'm not sure if there's a way to "disable component focus" or whether the usual workaround of TakeFocus() called by some other random (potentially invisible) component.

EDIT: It works! I accidentally used an InteractiveScreen initially. Using the plain Screen instead fixed it.

[mavam]

When I use Dimension::Full() as width, I still get the terminal size as upper bound. My expectation would be that I get the component width instead. Here's an example:

Since such output may be written to a file and users can use horizontal scrolling later on (e.g., less -S), I don't want to experience data loss due to cropping.

A workaround of Dimension::Fixed(some_high_value) unfortunately (a) does over-provisioning and (b) requires guesswork by the user. I tried switching my flex decorators to flex_grow, but it