Struct Buffer 

pub struct Buffer {
    pub text: String,
    pub cursor: usize,
    /* private fields */
}

Line-edit buffer for input composition. Byte-indexed cursor.

Large pasted blocks are folded into [Pasted #N +M lines] placeholders stored in text; the original contents live in pastes and are spliced back in when the line is submitted. This keeps the visible input short (matching CC’s paste UX) without truncating what the agent actually sees.

Fields

text: String

cursor: usize

Implementations

impl Buffer

pub fn is_in_history(&self) -> bool

True while the user is scrolling input history (Up/Down on an empty / non-empty buffer). The slash-command menu suppresses itself in this state so that recalling a previous /session foo from history doesn’t immediately re-pop the menu and trap Up inside it. Cleared automatically by Insert / Cancel (typing or Esc) and by HistoryNext returning past the newest entry to the user’s stashed draft.

pub fn history_idx(&self) -> Option<usize>

The index into history of the entry currently being displayed, or None if the buffer is showing the user’s own draft. Used by event_loop to look up HistoryEntry::images after every apply() so pending_recalled_attachments mirrors what the buffer is showing.

pub fn insert_paste(&mut self, text: String) -> String

Insert a pasted block. Folds into a [Pasted …] placeholder if the block exceeds the fold threshold, keeping the visible input terse. Returns the placeholder that was inserted (or the raw text for small pastes) so callers can advance the cursor.

Single-line long pastes (e.g. a 600-char URL) use a {N} chars summary — +1 lines would be misleading. Multi-line pastes use +{M} lines which is what people expect for code blocks / diffs.

Line-ending normalisation: most terminals in bracketed paste mode emit \r (or \r\n) between lines rather than \n. Without normalising, a 20-line paste looks like one gigantic line to str::lines() (returning count 1), and downstream agents may mis-handle payloads that mix CR-only separators. We fold \r\n and lone \r to \n at ingress so both the placeholder summary and the expanded agent payload are in canonical form.

pub fn cursor_line_up(&mut self) -> bool

Try to move the cursor up one logical line, preserving the column (measured in display cells so CJK lines up). Returns false only when the cursor is already at byte 0 — caller can then fall through to history navigation. Designed for the Up keystroke in multi-line composition: pressing Up walks the cursor through the buffer’s lines first, then snaps to the start of the first line, and only the next Up after that surfaces history. Costs one extra keystroke before history kicks in but rescues anyone who paged Up to fix a typo on line 1 from losing their draft.

pub fn cursor_line_down(&mut self) -> bool

Mirror of [cursor_line_up] for Down. Returns false only when the cursor is already at text.len() — caller then falls through to HistoryNext. On the last logical line, Down first snaps to end-of-buffer; the keystroke after that hands off to history.