Why do my text elements keep disappearing from the output every time a new one is added?

[mscofield0]

This is roughly what the add_message() function looks like:

std::string msg;
main_component_->message_component_->Add(ftxui::Renderer([msg] { return ftxui::text(msg); }));

And this is what the render function looks like:

auto App::Component::Render() -> ftxui::Element {
	using namespace ftxui;

	return vbox({
	  window(text("Logs"), log_component_->Render()) | flex,
	  window(text("Chat"), message_component_->Render()) | flex,
	  window(text("Input"), input_->Render()),
	});
}

With the component class being like this:

class Component : public ftxui::ComponentBase
{
	friend class App;
public:
	auto Render() -> ftxui::Element override;
	auto OnEvent(ftxui::Event evt) -> bool override;

private:
	ftxui::Component log_component_ = ftxui::Container::Vertical({});
	ftxui::Component message_component_ = ftxui::Container::Vertical({});
	std::string input_buf_;
	ftxui::Component input_ = ftxui::Input(&input_buf_, "Input here:", {});
};

[ArthurSonzogni]

How is the constructor written?

[mscofield0]

Tried with the example from here, it's definitely reproducible (the input not being cleared part):

std::string first_name;
std::string last_name;
std::string password;

InputOption opt;
opt.on_enter = [&first_name] { first_name.clear(); };
Component input_first_name = Input(&first_name, "first name", opt);
Component input_last_name = Input(&last_name, "last name");
Component input_password = Input(&password, "password");

auto component = Container::Vertical({
  input_first_name,
  input_last_name,
  input_password,
});

auto renderer = Renderer(component, [&] {
	return vbox({
			 text("Hello " + first_name + " " + last_name),
			 separator(),
			 hbox(text(" First name : "), input_first_name->Render()),
			 hbox(text(" Last name  : "), input_last_name->Render()),
			 hbox(text(" Password   : "), input_password->Render()),
		   }) |
	  border;
});

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

[mscofield0]

Hmm, this one doesn't show the same results as the original one, but it still doesn't work as expected:

Code:

std::string first_name;
std::string last_name;
std::string password;

Component list = Container::Vertical({});

InputOption opt;
opt.on_enter = [&first_name, &list] {
	list->Add(Renderer([&first_name] { return text(first_name); }));
	first_name.clear();
};
Component input_first_name = Input(&first_name, "first name", opt);
Component input_last_name = Input(&last_name, "last name");
Component input_password = Input(&password, "password");

auto component = Container::Vertical({
  input_first_name,
  input_last_name,
  input_password,
});

auto renderer = Renderer(component, [&] {
	return vbox({
			 window(text("List"), list->Render()),
			 text("Hello " + first_name + " " + last_name),
			 separator(),
			 hbox(text(" First name : "), input_first_name->Render()),
			 hbox(text(" Last name  : "), input_last_name->Render()),
			 hbox(text(" Password   : "), input_password->Render()),
		   }) |
	  border;
});

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

Update:
This can be fixed by passing a copy into the Renderer() lambda. Don't know why though, text() takes in a copy of the string, not a reference...

[mscofield0]

Okay fixed my original issue with output being erased. Apparently you can't move a std::string into text() for some reason.

[mscofield0]

Though I would like to find out a solution to erasing the input. @ArthurSonzogni

[ArthurSonzogni]

About Input, there is known bug. Trying to modify the string value during the on_enter event is ineffective.
#271

What can be done:

1. Wait for me to fix it.
2. Use the deprecated constructor from std::wstring instead of std::string.
3. Delay mutating the input into another task, outside of the on_enter function.

The issue is that the Input implementation is still made using std::wstring, and we "synchronize" manually back and forth during the OnEvent event:
https://github.com/ArthurSonzogni/FTXUI/blob/master/src/ftxui/component/input.cpp#L213