Struct TextareaState 

pub struct TextareaState {
    pub lines: Vec<String>,
    pub cursor_row: usize,
    pub cursor_col: usize,
    pub max_length: Option<usize>,
    pub wrap_width: Option<u32>,
    pub scroll_offset: usize,
    /* private fields */
}

State for a multi-line text area widget.

Pass a mutable reference to Context::textarea each frame along with the number of visible rows. The widget handles all keyboard events when focused.

Undo / redo

Ctrl+Z undoes the most recent edit and Ctrl+Y redoes it. The widget pushes a snapshot before every destructive mutation (char insert, delete, Enter, Backspace, paste). Rapid character typing coalesces into a single undoable batch — only the first char of a typing burst pushes a snapshot. History is capped at history_max entries (default 100); the oldest snapshot is dropped when the cap is exceeded.

Example

let mut state = TextareaState::new();
// Type, then press Ctrl+Z to undo or Ctrl+Y to redo.
ui.textarea(&mut state, 5);

Fields

lines: Vec<String>

The lines of text, one entry per line.

cursor_row: usize

Row index of the cursor (0-based, logical line).

cursor_col: usize

Column index of the cursor within the current row (character index).

max_length: Option<usize>

Maximum total character count across all lines.

wrap_width: Option<u32>

When set, lines longer than this display-column width are soft-wrapped.

scroll_offset: usize

First visible visual line (managed internally by textarea()).

Implementations

impl TextareaState

pub fn new() -> Self

Create an empty text area state with one blank line.

pub fn value(&self) -> String

Return all lines joined with newline characters.

pub fn set_value(&mut self, text: impl Into<String>)

Replace the content with the given text, splitting on newlines.

Resets the cursor to the beginning of the first line and clears the undo history — programmatic replacement is treated as a fresh state, not an undoable edit.

pub fn max_length(self, len: usize) -> Self

Set the maximum allowed total character count.

pub fn word_wrap(self, width: u32) -> Self

Enable soft word-wrap at the given display-column width.

pub fn history_max(self, cap: usize) -> Self

Override the maximum number of undo snapshots kept (default 100).

When the history exceeds this cap the oldest snapshot is dropped. Setting 0 disables undo recording — the field is read every keypress.

pub fn history_len(&self) -> usize

Number of undo snapshots currently retained.

Read-only — useful for tests and debugging the history cap. The cap itself is set via history_max.

pub fn history_cap(&self) -> usize

Maximum number of undo snapshots retained.

Mirrors history_max (the builder setter) but as a getter — useful for tests asserting the cap stays bounded.

Trait Implementations

impl Clone for TextareaState

fn clone(&self) -> TextareaState

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TextareaState

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TextareaState

fn default() -> Self

Returns the “default value” for a type.