The initial render of a session, and any re-draws caused by terminal
resizing are noticeably slow, especially on conversations with 20+
turns and many tool calls.
From profiling with `bun --cpu-prof` (available since bun 1.3.2), the
majority of the rendering (90%) is spent on detection of emojis in the
string-width library, running the expensive `/\p{RGI_Emoji}$/v`
regular expression on every individual grapheme cluster in the entire
scrollback. I believe it essentially expands to a fixed search against
every possible emoji sequence, hence the amount of CPU time spent in it.
This change replaces the `stringWidth` from string-width with a
`graphemeWidth` function that performs a similar check, but avoids
running the `/\p{RGI_Emoji}$/v` regex for emoji detection unless it
contains codepoints that could be emojis.
The `visibleWidth` function also has two more optimisations:
- Short-circuits string length detection for strings that are entirely
printable ASCII characters
- Adds a cache for non-ASCII segments to avoid recomputing string length
when resizing
Previously, the Editor component used character-level (grapheme-level)
wrapping, which broke words mid-character at line boundaries. This
created an ugly visual experience when typing or pasting long text.
Now the Editor uses word-aware wrapping:
- Wraps at word boundaries when possible
- Falls back to character-level wrapping for tokens wider than the
available width (e.g., long URLs)
- Strips leading whitespace at line starts
- Preserves multiple spaces within lines
Added wordWrapLine() helper function that tokenizes text into words
and whitespace runs, then builds chunks that fit within the specified
width while respecting word boundaries.
Also updated buildVisualLineMap() to use the same word wrapping logic
for consistent cursor navigation.
Added tests for:
- Word boundary wrapping
- Leading whitespace stripping
- Long token (URL) character-level fallback
- Multiple space preservation
- Edge cases (empty string, exact fit)
- Export wrapTextWithAnsi from tui package
- Add 'Handling Input' section to README with key detection example
- Document wrapTextWithAnsi in utilities section
