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Merge pull request #327 from chrisvest/avoid-grapheme-iteration

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Avoid iterating graphemes unless we have to.
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Alexandre Bury 2019-03-12 13:55:49 -07:00 committed by GitHub
commit e5ef01c90f
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1 changed files with 34 additions and 25 deletions
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59
src/printer.rs
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@ -129,46 +129,55 @@ impl<'a, 'b> Printer<'a, 'b> {
return;
}
let text_width = text.width();
let mut text_width = text.width();
// If we're waaaay too far left, just give up.
if hidden_part.x > text_width {
return;
}
let mut text = text;
let mut start = start;
if hidden_part.x > 0 {
// We have to drop hidden_part.x width from the start of the string.
// prefix() may be too short if there's a double-width character.
// So instead, keep the suffix and drop the prefix.
// We have to drop hidden_part.x width from the start of the string.
// prefix() may be too short if there's a double-width character.
// So instead, keep the suffix and drop the prefix.
// TODO: use a different prefix method that is *at least* the width
// (and not *at most*)
let tail =
suffix(text.graphemes(true), text_width - hidden_part.x, "");
let skipped_len = text.len() - tail.length;
let skipped_width = text_width - tail.width;
assert_eq!(text[..skipped_len].width(), skipped_width);
// TODO: use a different prefix method that is *at least* the width
// (and not *at most*)
let tail =
suffix(text.graphemes(true), text_width - hidden_part.x, "");
let skipped_len = text.len() - tail.length;
let skipped_width = text_width - tail.width;
assert_eq!(text[..skipped_len].width(), skipped_width);
// This should be equal most of the time, except when there's a double
// character preventing us from splitting perfectly.
assert!(skipped_width >= hidden_part.x);
// This should be equal most of the time, except when there's a double
// character preventing us from splitting perfectly.
assert!(skipped_width >= hidden_part.x);
// Drop part of the text, and move the cursor correspondingly.
let text = &text[skipped_len..];
let start = start + (skipped_width, 0);
// Drop part of the text, and move the cursor correspondingly.
text = &text[skipped_len..];
start = start + (skipped_width, 0);
text_width -= skipped_width;
}
assert!(start.fits(self.content_offset));
// What we did before should guarantee that this won't overflow.
let start = start - self.content_offset;
start = start - self.content_offset;
// Do we have enough room for the entire line?
let room = self.output_size.x - start.x;
// Drop the end of the text if it's too long
// We want the number of CHARACTERS, not bytes.
// (Actually we want the "width" of the string, see unicode-width)
let prefix_len = prefix(text.graphemes(true), room, "").length;
let text = &text[..prefix_len];
assert!(text.width() <= room);
if room < text_width {
// Drop the end of the text if it's too long
// We want the number of CHARACTERS, not bytes.
// (Actually we want the "width" of the string, see unicode-width)
let prefix_len = prefix(text.graphemes(true), room, "").length;
text = &text[..prefix_len];
assert!(text.width() <= room);
}
let start = start + self.offset;
self.backend.print_at(start, text);