Struct LogViewer 

pub struct LogViewer { /* private fields */ }

A scrolling log viewer optimized for streaming append-only content.

Internally uses Virtualized<Text> for storage and scroll management, adding capacity enforcement, wrapping, filtering, and search on top.

Design Rationale

• Virtualized handles scroll offset, follow mode, momentum, page navigation
• LogViewer adds max_lines eviction (Virtualized has no built-in capacity limit)
• Separate scroll semantics: Virtualized uses “offset from top”; LogViewer exposes “follow mode” (newest at bottom) as the default behavior
• wrap_mode configurable per-instance for different use cases
• Stateful widget pattern for scroll state preservation across renders

Implementations

impl LogViewer

pub fn new(max_lines: usize) -> Self

Create a new LogViewer with specified max line capacity.

Arguments

• max_lines - Maximum lines to retain. When exceeded, oldest lines are evicted. Recommend 10,000-100,000 for typical agent use cases.

pub fn wrap_mode(self, mode: LogWrapMode) -> Self

Set the wrap mode.

pub fn style(self, style: Style) -> Self

Set the default style for lines.

pub fn highlight_style(self, style: Style) -> Self

Set the highlight style for selected lines.

pub fn search_highlight_style(self, style: Style) -> Self

Set the highlight style for search matches within lines.

pub fn len(&self) -> usize

Returns the total number of log lines.

pub fn is_empty(&self) -> bool

Returns true if there are no log lines.

pub fn push(&mut self, line: impl Into<Text>)

Append a single log line.

Performance

• O(1) amortized for append
• O(1) for eviction when at capacity

Auto-scroll Behavior

If follow mode is enabled, view stays at bottom after push.

pub fn push_many(&mut self, lines: impl IntoIterator<Item = impl Into<Text>>)

Append multiple lines efficiently.

pub fn scroll_up(&mut self, lines: usize)

Scroll up by N lines. Disables follow mode.

pub fn scroll_down(&mut self, lines: usize)

Scroll down by N lines. Re-enables follow mode if at bottom.

pub fn scroll_to_top(&mut self)

Jump to top of log history.

pub fn scroll_to_bottom(&mut self)

Jump to bottom and re-enable follow mode.

pub fn page_up(&mut self, _state: &LogViewerState)

Page up (scroll by viewport height).

Uses the visible count tracked by the Virtualized container. The state parameter is accepted for API compatibility.

pub fn page_down(&mut self, _state: &LogViewerState)

Page down (scroll by viewport height).

Uses the visible count tracked by the Virtualized container. The state parameter is accepted for API compatibility.

pub fn is_at_bottom(&self) -> bool

Check if currently scrolled to the bottom.

Returns true when follow mode is active (even before first render when the viewport size is unknown).

pub fn line_count(&self) -> usize

Total line count in buffer.

pub fn auto_scroll_enabled(&self) -> bool

Check if follow mode (auto-scroll) is enabled.

pub fn set_auto_scroll(&mut self, enabled: bool)

Set follow mode (auto-scroll) state.

pub fn toggle_follow(&mut self)

Toggle follow mode on/off.

pub fn clear(&mut self)

Clear all lines.

pub fn filter_stats(&self) -> &FilterStats

Get a reference to the incremental filter/search statistics.

Use this to monitor how often the streaming incremental path is used versus full rescans.

pub fn filter_stats_mut(&mut self) -> &mut FilterStats

Get a mutable reference to the filter statistics (for resetting).

pub fn set_filter(&mut self, pattern: Option<&str>)

Set a filter pattern (plain substring match).

Only lines containing the pattern will be shown. Pass None to clear.

pub fn search(&mut self, query: &str) -> usize

Search for text and return match count.

Convenience wrapper using default config (literal, case-sensitive, no context). Sets up search state for navigation with next_match / prev_match.

pub fn search_with_config(&mut self, query: &str, config: SearchConfig) -> usize

Search with full configuration (mode, case sensitivity, context lines).

Returns match count. Sets up state for next_match / prev_match.

pub fn next_match(&mut self)

Jump to next search match.

pub fn prev_match(&mut self)

Jump to previous search match.

pub fn clear_search(&mut self)

Clear active search.

pub fn search_info(&self) -> Option<(usize, usize)>

Get current search match info: (current_match_1indexed, total_matches).

pub fn highlight_ranges_for_line( &self, line_idx: usize, ) -> Option<&[(usize, usize)]>

Get the highlight byte ranges for a given line index, if any.

Returns Some(&[(start, end)]) when the line is a search match.

pub fn context_line_indices(&self) -> Option<&[usize]>

Get the context-expanded line indices, if context lines are configured.

Returns None when no search is active or context_lines == 0.

pub fn search_match_rate_hint(&self) -> f64

Returns the fraction of recent pushes that matched the active search.

Useful for callers integrating with an EProcessThrottle to decide when to trigger a full UI refresh vs. deferring. Returns 0.0 when no search is active or no incremental checks occurred.

Trait Implementations

impl Clone for LogViewer

fn clone(&self) -> LogViewer

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for LogViewer

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

Formats the value using the given formatter.

impl StatefulWidget for LogViewer

type State = LogViewerState

The state type associated with this widget.

fn render(&self, area: Rect, frame: &mut Frame<'_>, state: &mut Self::State)

Render the widget into the frame, potentially modifying state.