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// Based on https://github.com/cessen/led/blob/c4fa72405f510b7fd16052f90a598c429b3104a6/src/graphemes.rs
use ropey::{iter::Chunks, str_utils::byte_to_char_idx, RopeSlice};
use unicode_segmentation::{GraphemeCursor, GraphemeIncomplete};
use unicode_width::UnicodeWidthStr;
pub fn grapheme_width(g: &str) -> usize {
if g.as_bytes()[0] <= 127 {
// Fast-path ascii.
// Point 1: theoretically, ascii control characters should have zero
// width, but in our case we actually want them to have width: if they
// show up in text, we want to treat them as textual elements that can
// be editied. So we can get away with making all ascii single width
// here.
// Point 2: we're only examining the first codepoint here, which means
// we're ignoring graphemes formed with combining characters. However,
// if it starts with ascii, it's going to be a single-width grapeheme
// regardless, so, again, we can get away with that here.
// Point 3: we're only examining the first _byte_. But for utf8, when
// checking for ascii range values only, that works.
1
} else {
// We use max(1) here because all grapeheme clusters--even illformed
// ones--should have at least some width so they can be edited
// properly.
UnicodeWidthStr::width(g).max(1)
}
}
pub fn nth_prev_grapheme_boundary(slice: RopeSlice, char_idx: usize, n: usize) -> usize {
// TODO: implement this more efficiently. This has to do a lot of
// re-scanning of rope chunks. Probably move the main implementation here,
// and have prev_grapheme_boundary call this instead.
let mut char_idx = char_idx;
for _ in 0..n {
char_idx = prev_grapheme_boundary(slice, char_idx);
}
char_idx
}
/// Finds the previous grapheme boundary before the given char position.
pub fn prev_grapheme_boundary(slice: RopeSlice, char_idx: usize) -> usize {
// Bounds check
debug_assert!(char_idx <= slice.len_chars());
// We work with bytes for this, so convert.
let byte_idx = slice.char_to_byte(char_idx);
// Get the chunk with our byte index in it.
let (mut chunk, mut chunk_byte_idx, mut chunk_char_idx, _) = slice.chunk_at_byte(byte_idx);
// Set up the grapheme cursor.
let mut gc = GraphemeCursor::new(byte_idx, slice.len_bytes(), true);
// Find the previous grapheme cluster boundary.
loop {
match gc.prev_boundary(chunk, chunk_byte_idx) {
Ok(None) => return 0,
Ok(Some(n)) => {
let tmp = byte_to_char_idx(chunk, n - chunk_byte_idx);
return chunk_char_idx + tmp;
}
Err(GraphemeIncomplete::PrevChunk) => {
let (a, b, c, _) = slice.chunk_at_byte(chunk_byte_idx - 1);
chunk = a;
chunk_byte_idx = b;
chunk_char_idx = c;
}
Err(GraphemeIncomplete::PreContext(n)) => {
let ctx_chunk = slice.chunk_at_byte(n - 1).0;
gc.provide_context(ctx_chunk, n - ctx_chunk.len());
}
_ => unreachable!(),
}
}
}
pub fn nth_next_grapheme_boundary(slice: RopeSlice, char_idx: usize, n: usize) -> usize {
// TODO: implement this more efficiently. This has to do a lot of
// re-scanning of rope chunks. Probably move the main implementation here,
// and have next_grapheme_boundary call this instead.
let mut char_idx = char_idx;
for _ in 0..n {
char_idx = next_grapheme_boundary(slice, char_idx);
}
char_idx
}
/// Finds the next grapheme boundary after the given char position.
pub fn next_grapheme_boundary(slice: RopeSlice, char_idx: usize) -> usize {
// Bounds check
debug_assert!(char_idx <= slice.len_chars());
// We work with bytes for this, so convert.
let byte_idx = slice.char_to_byte(char_idx);
// Get the chunk with our byte index in it.
let (mut chunk, mut chunk_byte_idx, mut chunk_char_idx, _) = slice.chunk_at_byte(byte_idx);
// Set up the grapheme cursor.
let mut gc = GraphemeCursor::new(byte_idx, slice.len_bytes(), true);
// Find the next grapheme cluster boundary.
loop {
match gc.next_boundary(chunk, chunk_byte_idx) {
Ok(None) => return slice.len_chars(),
Ok(Some(n)) => {
let tmp = byte_to_char_idx(chunk, n - chunk_byte_idx);
return chunk_char_idx + tmp;
}
Err(GraphemeIncomplete::NextChunk) => {
chunk_byte_idx += chunk.len();
let (a, _, c, _) = slice.chunk_at_byte(chunk_byte_idx);
chunk = a;
chunk_char_idx = c;
}
Err(GraphemeIncomplete::PreContext(n)) => {
let ctx_chunk = slice.chunk_at_byte(n - 1).0;
gc.provide_context(ctx_chunk, n - ctx_chunk.len());
}
_ => unreachable!(),
}
}
}
/// Returns whether the given char position is a grapheme boundary.
pub fn is_grapheme_boundary(slice: RopeSlice, char_idx: usize) -> bool {
// Bounds check
debug_assert!(char_idx <= slice.len_chars());
// We work with bytes for this, so convert.
let byte_idx = slice.char_to_byte(char_idx);
// Get the chunk with our byte index in it.
let (chunk, chunk_byte_idx, _, _) = slice.chunk_at_byte(byte_idx);
// Set up the grapheme cursor.
let mut gc = GraphemeCursor::new(byte_idx, slice.len_bytes(), true);
// Determine if the given position is a grapheme cluster boundary.
loop {
match gc.is_boundary(chunk, chunk_byte_idx) {
Ok(n) => return n,
Err(GraphemeIncomplete::PreContext(n)) => {
let (ctx_chunk, ctx_byte_start, _, _) = slice.chunk_at_byte(n - 1);
gc.provide_context(ctx_chunk, ctx_byte_start);
}
_ => unreachable!(),
}
}
}
/// An iterator over the graphemes of a RopeSlice.
#[derive(Clone)]
pub struct RopeGraphemes<'a> {
text: RopeSlice<'a>,
chunks: Chunks<'a>,
cur_chunk: &'a str,
cur_chunk_start: usize,
cursor: GraphemeCursor,
}
impl<'a> RopeGraphemes<'a> {
pub fn new(slice: RopeSlice) -> RopeGraphemes {
let mut chunks = slice.chunks();
let first_chunk = chunks.next().unwrap_or("");
RopeGraphemes {
text: slice,
chunks,
cur_chunk: first_chunk,
cur_chunk_start: 0,
cursor: GraphemeCursor::new(0, slice.len_bytes(), true),
}
}
}
impl<'a> Iterator for RopeGraphemes<'a> {
type Item = RopeSlice<'a>;
fn next(&mut self) -> Option<RopeSlice<'a>> {
let a = self.cursor.cur_cursor();
let b;
loop {
match self
.cursor
.next_boundary(self.cur_chunk, self.cur_chunk_start)
{
Ok(None) => {
return None;
}
Ok(Some(n)) => {
b = n;
break;
}
Err(GraphemeIncomplete::NextChunk) => {
self.cur_chunk_start += self.cur_chunk.len();
self.cur_chunk = self.chunks.next().unwrap_or("");
}
_ => unreachable!(),
}
}
if a < self.cur_chunk_start {
let a_char = self.text.byte_to_char(a);
let b_char = self.text.byte_to_char(b);
Some(self.text.slice(a_char..b_char))
} else {
let a2 = a - self.cur_chunk_start;
let b2 = b - self.cur_chunk_start;
Some((&self.cur_chunk[a2..b2]).into())
}
}
}
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