TextInput Submit Pattern

textInput(state).onSubmit(...) takes a Runnable, not a Consumer<String>. The submitted text is read out of the bound TextInputState, not passed as a callback argument. Why: most TUI libraries pass the submitted line into the handler; TamboUI does not, and writing the more familiar onSubmit { line -> ... } produces either a compile error or a handler that runs but never sees the text — both look like "submit doesn't work."

The Correct Shape

val state = textInputState()
textInput(state).onSubmit(Runnable {
    val line = state.text()
    if (line.isNotBlank()) {
        send(line)
    }
    state.clear()
})

Java equivalent:

TextInputState state = textInputState();
textInput(state).onSubmit(() -> {
    String line = state.text();
    if (!line.isEmpty()) {
        send(line);
    }
    state.clear();
});

Why Read From State, Not From a Callback Arg

• TextInputState is the source of truth for the buffer and cursor — reading from there is the same source the next render uses
• Passing the line into the callback would require copying it out of state into the call frame, then the handler still has to call state.clear() to reset for the next line — two operations where one suffices

Always Clear After Submit

• state.clear() is mandatory at the end of the handler unless you want the previous line to persist visibly in the input box
• If the field is held as private val state: TextInputState (see [[persistent-stateful-elements]]), the handler can safely reference it directly

Mistakes the Compiler Catches

• .onSubmit { line -> ... } (lambda taking a String) — compile error: Runnable is zero-arg
• .onSubmit(Consumer<String> { ... }) — compile error: wrong type

Mistakes the Compiler Does Not Catch

• Forgetting state.clear() — input keeps accumulating across submits
• Holding a fresh textInput(textInputState()) inline in render() — the state object is discarded every frame, see [[persistent-stateful-elements]]