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