Text disappears randomly

[BritishTeapot]

Hello! I am just starting with FTXUI, and tried to make a quick AI chat app.

However, I have encountered an issue that my text sometimes disappears for no apparent reason:

The grey boxes are supposed to contain user messages (expected behavior). Instead, the text disappears, and only the grey boxes remain

Here is the offending code:

#include "ftxui/component/component.hpp"
#include "ftxui/component/component_base.hpp"
#include "ftxui/component/component_options.hpp"
#include "ftxui/component/event.hpp"
#include "ftxui/component/screen_interactive.hpp"
#include "ftxui/dom/elements.hpp"
//#include "openai/openai.hpp"
#include <ftxui/dom/elements.hpp>
#include <ftxui/screen/screen.hpp>
#include <iostream>
#include <string>
#include <vector>

std::string get_ai_response(std::vector<std::string> messages) {

  // requests provider for an answer. Returns some multiline string

  return "I am a helpful assistant! \n Let me know what you need help with today."
}

int main(void) {
  using namespace ftxui;

  // define the buffer at the top
  std::vector<std::string> message_list;

  // the actual input area
  std::string input_text = "I am input text";
  InputOption input_option = InputOption::Default();

  auto input = Input(&input_text, input_option);

  input |= CatchEvent([&](Event event) {
    if (event == Event::Return) {
      message_list.push_back(input_text);

      std::string response = get_ai_response(message_list);
      message_list.push_back(response);

      input_text = "";
      return true;
    }
    return false;
  });

  auto component = Container::Vertical({
                       input,
                   }) |
                   size(HEIGHT, GREATER_THAN, 3);

  // Tweak how the component tree is rendered:
  auto renderer = Renderer(component, [&] {

    // it's not very efficient way to render this, but I don't see why this shouldn't work

    auto n_messages = message_list.size();
    std::vector<Element> message_history;
    message_history.reserve(n_messages);

    for (int i = 0; i < n_messages; i++) {
      if (i % 2) {
        message_history.push_back(paragraph(message_list[i]));
      } else {
        message_history.push_back(paragraph(message_list[i]) |
                                  borderStyled(LIGHT, Color::GrayDark));
      }
    }

    return vbox({vbox(message_history), separator(), component->Render()});
  });

  auto screen = ScreenInteractive::TerminalOutput();
  screen.Loop(renderer);
  return EXIT_SUCCESS;
}

I am using version 6.1.9 downloaded from GitHub releases, and running under Linux in Ptyxis 49.3 and Ghostty 1.3.1-1.fc43.

[ArthurSonzogni]

By default, FTXUI doesn't overflow. So it when the screen is too small, it will shrink elements.

You probably want to wrap the final layout with ... | vscroll_indicator | frame | size(HEIGHT, LESS_THAN, 10) | border

See examples:

• https://arthursonzogni.github.io/FTXUI/examples_2component_2radiobox_in_frame_8cpp-example.html
• https://arthursonzogni.github.io/FTXUI/examples_2component_2scrollbar_8cpp-example.html

See also:

• https://github.com/ArthurSonzogni/git-tui/blob/master/src/scroller.cpp

[BritishTeapot]

TYSM for help (@^v^)/

I tried your solution, but that's not really what I want to achieve. I don't want FTXUI's scrolling, I want everything to overflow, and use the terminal emulator's scrolling.

Here is an example of what I am thinking about:

Screencast.From.2026-05-20.07-59-54.mp4

Is this possible with FTXUI?

[ArthurSonzogni]

Is this possible with FTXUI?

Not at the moment. We would have to add this feature.

We support:

1. Drawing into the alternate buffer.
2. Drawing into the regular buffer in a "Print, Track, and Rewind" Cycle.

However in (2), we always clear the previous frame fully before drawing the new one. It means we can't really "push" some static element above.

I think we would like to add support for having the dynamic component drawn like it is today, but an API to append some static Element above it.

Would you be interested?

[BritishTeapot]

I would really like to work on implementing this feature myself, even if I did not understand a single thing in your explanation for why it doesn't work now :) I would need to take some time to familiarize myself with the codebase first