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fix(graphical): Align highlights correctly with wide unicode characte…
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…rs and tabs (#202)

Fixes: #97
Fixes: #87

Tabs are always expanded to spaces by the graphical handler, and `tab_width` now defaults to 4. Instead of replacing every tab with a fixed number of spaces, spaces are used to align to the next tabstop. `tab_width` controls the space between tabstops rather than the fixed width of each tab character.

Co-authored-by: Benjamin Lee <benjamin@computer.surgery>
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@olivia-fl
olivia-fl and olivia-fl authored Sep 10, 2022
1 parent 5f3429b commit 196c09c
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Showing 2 changed files with 85 additions and 68 deletions.
141 changes: 79 additions & 62 deletions src/handlers/graphical.rs
View file
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
use std::fmt::{self, Write};

use owo_colors::{OwoColorize, Style};
use unicode_width::UnicodeWidthChar;

use crate::diagnostic_chain::DiagnosticChain;
use crate::handlers::theme::*;
Expand All @@ -27,7 +28,7 @@ pub struct GraphicalReportHandler {
pub(crate) theme: GraphicalTheme,
pub(crate) footer: Option<String>,
pub(crate) context_lines: usize,
pub(crate) tab_width: Option<usize>,
pub(crate) tab_width: usize,
pub(crate) with_cause_chain: bool,
}

Expand All @@ -48,7 +49,7 @@ impl GraphicalReportHandler {
theme: GraphicalTheme::default(),
footer: None,
context_lines: 1,
tab_width: None,
tab_width: 4,
with_cause_chain: true,
}
}
Expand All @@ -61,14 +62,14 @@ impl GraphicalReportHandler {
theme,
footer: None,
context_lines: 1,
tab_width: None,
tab_width: 4,
with_cause_chain: true,
}
}

/// Set the displayed tab width in spaces.
pub fn tab_width(mut self, width: usize) -> Self {
self.tab_width = Some(width);
self.tab_width = width;
self
}

Expand Down Expand Up @@ -441,12 +442,7 @@ impl GraphicalReportHandler {
self.render_line_gutter(f, max_gutter, line, &labels)?;

// And _now_ we can print out the line text itself!
if let Some(w) = self.tab_width {
let text = line.text.replace('\t', " ".repeat(w).as_str());
writeln!(f, "{}", text)?;
} else {
writeln!(f, "{}", line.text)?;
};
self.render_line_text(f, &line.text)?;

// Next, we write all the highlights that apply to this particular line.
let (single_line, multi_line): (Vec<_>, Vec<_>) = labels
Expand Down Expand Up @@ -604,6 +600,46 @@ impl GraphicalReportHandler {
Ok(())
}

/// Returns an iterator over the visual width of each character in a line.
fn line_visual_char_width<'a>(&self, text: &'a str) -> impl Iterator<Item = usize> + 'a {
let mut column = 0;
let tab_width = self.tab_width;
text.chars().map(move |c| {
let width = if c == '\t' {
// Round up to the next multiple of tab_width
tab_width - column % tab_width
} else {
c.width().unwrap_or(0)
};
column += width;
width
})
}

/// Returns the visual column position of a byte offset on a specific line.
fn visual_offset(&self, line: &Line, offset: usize) -> usize {
let line_range = line.offset..(line.offset + line.length);
assert!(line_range.contains(&offset));

let text = &line.text[..offset - line.offset];
self.line_visual_char_width(text).sum()
}

/// Renders a line to the output formatter, replacing tabs with spaces.
fn render_line_text(&self, f: &mut impl fmt::Write, text: &str) -> fmt::Result {
for (c, width) in text.chars().zip(self.line_visual_char_width(text)) {
if c == '\t' {
for _ in 0..width {
f.write_char(' ')?
}
} else {
f.write_char(c)?
}
}
f.write_char('\n')?;
Ok(())
}

fn render_single_line_highlights(
&self,
f: &mut impl fmt::Write,
Expand All @@ -617,63 +653,44 @@ impl GraphicalReportHandler {
let mut highest = 0;

let chars = &self.theme.characters;
for hl in single_liners {
let hl_len = std::cmp::max(1, hl.len());

let local_offset = if let Some(w) = self.tab_width {
// Only count tabs that affect the position of the highlighted
// line and ignore tabs past the span.
let tab_count = &line.text[..hl.offset() - line.offset].matches('\t').count();
let tabs_as_spaces = tab_count * w - tab_count;
hl.offset() - line.offset + tabs_as_spaces
} else {
hl.offset() - line.offset
};

let vbar_offset = local_offset + (hl_len / 2);
let num_left = vbar_offset - local_offset;
let num_right = local_offset + hl_len - vbar_offset - 1;
let start = std::cmp::max(local_offset, highest);
let end = local_offset + hl_len;
if start < end {
underlines.push_str(
&format!(
"{:width$}{}{}{}",
"",
chars.underline.to_string().repeat(num_left),
if hl.len() == 0 {
chars.uarrow
} else if hl.label().is_some() {
chars.underbar
} else {
chars.underline
},
chars.underline.to_string().repeat(num_right),
width = local_offset.saturating_sub(highest),
)
.style(hl.style)
.to_string(),
);
}
highest = std::cmp::max(highest, end);
}
writeln!(f, "{}", underlines)?;

let vbar_offsets: Vec<_> = single_liners
.iter()
.map(|hl| {
let local_offset = if let Some(w) = self.tab_width {
// Only count tabs that affect the position of the
// highlighted line and ignore tabs past the span.
let tab_count = &line.text[..hl.offset() - line.offset].matches('\t').count();
let tabs_as_spaces = tab_count * w - tab_count;
hl.offset() - line.offset + tabs_as_spaces
} else {
hl.offset() - line.offset
};
(hl, local_offset + (std::cmp::max(1, hl.len()) / 2))
let byte_start = hl.offset();
let byte_end = hl.offset() + hl.len().max(1);
let start = self.visual_offset(line, byte_start).max(highest);
let end = self.visual_offset(line, byte_end);

let vbar_offset = (start + end) / 2;
let num_left = vbar_offset - start;
let num_right = end - vbar_offset - 1;
if start < end {
underlines.push_str(
&format!(
"{:width$}{}{}{}",
"",
chars.underline.to_string().repeat(num_left),
if hl.len() == 0 {
chars.uarrow
} else if hl.label().is_some() {
chars.underbar
} else {
chars.underline
},
chars.underline.to_string().repeat(num_right),
width = start.saturating_sub(highest),
)
.style(hl.style)
.to_string(),
);
}
highest = std::cmp::max(highest, end);

(hl, vbar_offset)
})
.collect();
writeln!(f, "{}", underlines)?;

for hl in single_liners.iter().rev() {
if let Some(label) = hl.label() {
self.write_no_linum(f, linum_width)?;
Expand Down
12 changes: 6 additions & 6 deletions tests/graphical.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,7 @@ fn single_line_with_wide_char() -> Result<(), MietteError> {
let src = "source\n 👼🏼text\n here".to_string();
let err = MyBad {
src: NamedSource::new("bad_file.rs", src),
highlight: (9, 6).into(),
highlight: (13, 8).into(),
};
let out = fmt_report(err.into());
println!("Error: {}", out);
Expand All @@ -92,8 +92,8 @@ fn single_line_with_wide_char() -> Result<(), MietteError> {
╭─[bad_file.rs:1:1]
1 │ source
2 │ 👼🏼text
· ───┬──
· ╰── this bit here
· ───┬──
· ╰── this bit here
3 │ here
╰────
help: try doing it better next time?
Expand Down Expand Up @@ -157,10 +157,10 @@ fn single_line_with_tab_in_middle() -> Result<(), MietteError> {

std::env::set_var("REPLACE_TABS", "4");

let src = "source\ntext\ttext\n here".to_string();
let src = "source\ntext =\ttext\n here".to_string();
let err = MyBad {
src: NamedSource::new("bad_file.rs", src),
highlight: (12, 4).into(),
highlight: (14, 4).into(),
};
let out = fmt_report(err.into());
println!("Error: {}", out);
Expand All @@ -169,7 +169,7 @@ fn single_line_with_tab_in_middle() -> Result<(), MietteError> {
× oops!
╭─[bad_file.rs:1:1]
1 │ source
2 │ text text
2 │ text = text
· ──┬─
· ╰── this bit here
3 │ here
Expand Down

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