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use unicode_width::UnicodeWidthStr;
/// Scroll position and geometry for a vertical scroll view.
#[derive(Clone, Copy, Debug, Default)]
pub struct ScrollViewState {
pub scroll: u16,
pub viewport_h: u16,
pub content_h: u16,
}
impl ScrollViewState {
pub fn clamp(&mut self) {
let max_scroll = self.content_h.saturating_sub(self.viewport_h);
if self.scroll > max_scroll {
self.scroll = max_scroll;
}
}
}
/// A simple, local scrollable view for diffs or message text.
///
/// Owns raw lines, caches wrapped lines for a given width, and maintains
/// a small scroll state that is clamped whenever geometry shrinks.
#[derive(Clone, Debug, Default)]
pub struct ScrollableDiff {
raw: Vec<String>,
wrapped: Vec<String>,
wrapped_src_idx: Vec<usize>,
wrap_cols: Option<u16>,
pub state: ScrollViewState,
}
impl ScrollableDiff {
pub fn new() -> Self {
Self::default()
}
/// Replace the raw content lines. Does not rewrap immediately; call `set_width` next.
pub fn set_content(&mut self, lines: Vec<String>) {
self.raw = lines;
self.wrapped.clear();
self.wrapped_src_idx.clear();
self.state.content_h = 0;
// Force rewrap on next set_width even if width is unchanged
self.wrap_cols = None;
}
/// Set the wrap width. If changed, rebuild wrapped lines and clamp scroll.
pub fn set_width(&mut self, width: u16) {
if self.wrap_cols == Some(width) {
return;
}
self.wrap_cols = Some(width);
self.rewrap(width);
self.state.clamp();
}
/// Update viewport height and clamp scroll if needed.
pub fn set_viewport(&mut self, height: u16) {
self.state.viewport_h = height;
self.state.clamp();
}
/// Return the cached wrapped lines. Call `set_width` first when area changes.
pub fn wrapped_lines(&self) -> &[String] {
&self.wrapped
}
pub fn wrapped_src_indices(&self) -> &[usize] {
&self.wrapped_src_idx
}
pub fn raw_line_at(&self, idx: usize) -> &str {
self.raw.get(idx).map(String::as_str).unwrap_or("")
}
/// Scroll by a signed delta; clamps to content.
pub fn scroll_by(&mut self, delta: i16) {
let s = self.state.scroll as i32 + delta as i32;
self.state.scroll = s.clamp(0, self.max_scroll() as i32) as u16;
}
/// Page by a signed delta; typically viewport_h - 1.
pub fn page_by(&mut self, delta: i16) {
self.scroll_by(delta);
}
pub fn scroll_to_top(&mut self) {
self.state.scroll = 0;
}
pub fn scroll_to_bottom(&mut self) {
self.state.scroll = self.max_scroll();
}
/// Optional percent scrolled; None when not enough geometry is known.
pub fn percent_scrolled(&self) -> Option<u8> {
if self.state.content_h == 0 || self.state.viewport_h == 0 {
return None;
}
if self.state.content_h <= self.state.viewport_h {
return None;
}
let visible_bottom = self.state.scroll.saturating_add(self.state.viewport_h) as f32;
let pct = (visible_bottom / self.state.content_h as f32 * 100.0).round();
Some(pct.clamp(0.0, 100.0) as u8)
}
fn max_scroll(&self) -> u16 {
self.state.content_h.saturating_sub(self.state.viewport_h)
}
fn rewrap(&mut self, width: u16) {
if width == 0 {
self.wrapped = self.raw.clone();
self.state.content_h = self.wrapped.len() as u16;
return;
}
let max_cols = width as usize;
let mut out: Vec<String> = Vec::new();
let mut out_idx: Vec<usize> = Vec::new();
for (raw_idx, raw) in self.raw.iter().enumerate() {
// Normalize tabs for width accounting (MVP: 4 spaces).
let raw = raw.replace('\t', " ");
if raw.is_empty() {
out.push(String::new());
out_idx.push(raw_idx);
continue;
}
let mut line = String::new();
let mut line_cols = 0usize;
let mut last_soft_idx: Option<usize> = None; // last whitespace or punctuation break
for grapheme in raw
.graphemes(/*is_extended*/ true)
.flat_map(|grapheme| grapheme.split_inclusive(char::is_whitespace))
{
if grapheme == "\n" {
out.push(std::mem::take(&mut line));
out_idx.push(raw_idx);
line_cols = 0;
last_soft_idx = None;
continue;
}
let grapheme_width = display_width(grapheme);
if line_cols.saturating_add(grapheme_width) > max_cols {
if let Some(split) = last_soft_idx {
let (prefix, rest) = line.split_at(split);
let prefix = prefix.trim_end();
if !prefix.is_empty() {
out.push(prefix.to_string());
out_idx.push(raw_idx);
}
line = rest.trim_start().to_string();
last_soft_idx = None;
// Retry adding the current grapheme now that the line may be shorter.
} else if !line.is_empty() {
out.push(std::mem::take(&mut line));
out_idx.push(raw_idx);
}
}
if grapheme.chars().all(char::is_whitespace)
|| grapheme.chars().any(|ch| {
matches!(
ch,
',' | ';'
| '.'
| ':'
| ')'
| ']'
| '}'
| '|'
| '/'
| '?'
| '!'
| '-'
| '_'
)
})
{
last_soft_idx = Some(line.len());
}
line.push_str(grapheme);
line_cols = display_width(&line);
}
if !line.is_empty() {
out.push(line);
out_idx.push(raw_idx);
}
}
self.wrapped = out;
self.wrapped_src_idx = out_idx;
self.state.content_h = self.wrapped.len() as u16;
}
}
/// Counts terminal cells, including the halfwidth sound marks omitted by `unicode-width`.
fn display_width(text: &str) -> usize {
UnicodeWidthStr::width(text)
+ text
.chars()
.filter(|ch| matches!(ch, '\u{FF9E}' | '\u{FF9F}'))
.count()
}
#[cfg(test)]
#[path = "scrollable_diff_tests.rs"]
mod tests;
|