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Improve word wrapping

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Now supports long trailing whitespace as well as tabs.
This commit is contained in:
Joscha 2022-07-04 18:56:52 +02:00
parent 9b0d80873f
commit 11b2211fad
5 changed files with 106 additions and 41 deletions
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72
src/wrap.rs
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@ -5,9 +5,11 @@ use unicode_segmentation::UnicodeSegmentation;
use crate::widthdb::WidthDB;
// TODO Handle tabs separately?
// TODO Convert into an iterator?
pub fn wrap(text: &str, width: usize, widthdb: &mut WidthDB) -> Vec<usize> {
pub fn tab_width_at_column(tab_width: u8, col: usize) -> u8 {
tab_width - (col % tab_width as usize) as u8
}
pub fn wrap(widthdb: &mut WidthDB, tab_width: u8, text: &str, width: usize) -> Vec<usize> {
let mut breaks = vec![];
let mut break_options = unicode_linebreak::linebreaks(text).peekable();
@ -16,8 +18,10 @@ pub fn wrap(text: &str, width: usize, widthdb: &mut WidthDB) -> Vec<usize> {
let mut valid_break = None;
let mut valid_break_width = 0;
// Width of the line at the current grapheme
// Width of the line at the current grapheme (with and without trailing
// whitespace)
let mut current_width = 0;
let mut current_width_trimmed = 0;
for (gi, g) in text.grapheme_indices(true) {
// Advance break options
@ -38,6 +42,7 @@ pub fn wrap(text: &str, width: usize, widthdb: &mut WidthDB) -> Vec<usize> {
valid_break = None;
valid_break_width = 0;
current_width = 0;
current_width_trimmed = 0;
}
BreakOpportunity::Allowed => {
valid_break = Some(bi);
@ -46,31 +51,52 @@ pub fn wrap(text: &str, width: usize, widthdb: &mut WidthDB) -> Vec<usize> {
}
}
let grapheme_width: usize = widthdb.grapheme_width(g).into();
if current_width + grapheme_width > width {
if current_width == 0 {
// The grapheme is wider than the maximum width, so we'll allow
// it, thereby forcing the following grapheme to break no matter
// what (either because of a mandatory or allowed break, or via
// a forced break).
} else if let Some(bi) = valid_break {
// We can't fit the grapheme onto the current line, so we'll
// just break at the last valid break point.
// Calculate widths after current grapheme
let g_width = if g == "\t" {
tab_width_at_column(tab_width, current_width) as usize
} else {
widthdb.grapheme_width(g) as usize
};
let mut new_width = current_width + g_width;
let mut new_width_trimmed = if g.chars().all(|c| c.is_whitespace()) {
current_width_trimmed
} else {
new_width
};
// Wrap at last break point if necessary
if new_width_trimmed > width {
if let Some(bi) = valid_break {
breaks.push(bi);
current_width -= valid_break_width;
new_width -= valid_break_width;
new_width_trimmed = new_width_trimmed.saturating_sub(valid_break_width);
valid_break = None;
valid_break_width = 0;
} else {
// Forced break in the midde of a normally non-breakable chunk
// because there have been no valid break points yet.
breaks.push(gi);
valid_break = None;
valid_break_width = 0;
current_width = 0;
}
}
current_width += grapheme_width;
// Perform a forced break if still necessary
if new_width_trimmed > width {
if new_width == g_width {
// The grapheme is the only thing on the current line and it is
// wider than the maximum width, so we'll allow it, thereby
// forcing the following grapheme to break no matter what
// (either because of a mandatory or allowed break, or via a
// forced break).
} else {
// Forced break in the midde of a normally non-breakable chunk
// because there are no valid break points.
breaks.push(gi);
new_width = 0;
new_width_trimmed = 0;
valid_break = None;
valid_break_width = 0;
}
}
// Update current width
current_width = new_width;
current_width_trimmed = new_width_trimmed;
}
breaks