annotate_snippets/renderer/
margin.rs

1use std::cmp::{max, min};
2
3const ELLIPSIS_PASSING: usize = 6;
4const LONG_WHITESPACE: usize = 20;
5const LONG_WHITESPACE_PADDING: usize = 4;
6
7#[derive(Clone, Copy, Debug, PartialEq)]
8pub(crate) struct Margin {
9    /// The available whitespace in the left that can be consumed when centering.
10    whitespace_left: usize,
11    /// The column of the beginning of left-most span.
12    span_left: usize,
13    /// The column of the end of right-most span.
14    span_right: usize,
15    /// The beginning of the line to be displayed.
16    computed_left: usize,
17    /// The end of the line to be displayed.
18    computed_right: usize,
19    /// The current width of the terminal. 140 by default and in tests.
20    pub(crate) term_width: usize,
21    /// The end column of a span label, including the span. Doesn't account for labels not in the
22    /// same line as the span.
23    label_right: usize,
24}
25
26impl Margin {
27    pub(crate) fn new(
28        whitespace_left: usize,
29        span_left: usize,
30        span_right: usize,
31        label_right: usize,
32        term_width: usize,
33        max_line_len: usize,
34    ) -> Self {
35        // The 6 is padding to give a bit of room for `...` when displaying:
36        // ```
37        // error: message
38        //   --> file.rs:16:58
39        //    |
40        // 16 | ... fn foo(self) -> Self::Bar {
41        //    |                     ^^^^^^^^^
42        // ```
43
44        let mut m = Margin {
45            whitespace_left: whitespace_left.saturating_sub(ELLIPSIS_PASSING),
46            span_left: span_left.saturating_sub(ELLIPSIS_PASSING),
47            span_right: span_right + ELLIPSIS_PASSING,
48            computed_left: 0,
49            computed_right: 0,
50            term_width,
51            label_right: label_right + ELLIPSIS_PASSING,
52        };
53        m.compute(max_line_len);
54        m
55    }
56
57    pub(crate) fn was_cut_left(&self) -> bool {
58        self.computed_left > 0
59    }
60
61    fn compute(&mut self, max_line_len: usize) {
62        // When there's a lot of whitespace (>20), we want to trim it as it is useless.
63        self.computed_left = if self.whitespace_left > LONG_WHITESPACE {
64            self.whitespace_left - (LONG_WHITESPACE - LONG_WHITESPACE_PADDING) // We want some padding.
65        } else {
66            0
67        };
68        // We want to show as much as possible, max_line_len is the right-most boundary for the
69        // relevant code.
70        self.computed_right = max(max_line_len, self.computed_left);
71
72        if self.computed_right - self.computed_left > self.term_width {
73            // Trimming only whitespace isn't enough, let's get craftier.
74            if self.label_right - self.whitespace_left <= self.term_width {
75                // Attempt to fit the code window only trimming whitespace.
76                self.computed_left = self.whitespace_left;
77                self.computed_right = self.computed_left + self.term_width;
78            } else if self.label_right - self.span_left <= self.term_width {
79                // Attempt to fit the code window considering only the spans and labels.
80                let padding_left = (self.term_width - (self.label_right - self.span_left)) / 2;
81                self.computed_left = self.span_left.saturating_sub(padding_left);
82                self.computed_right = self.computed_left + self.term_width;
83            } else if self.span_right - self.span_left <= self.term_width {
84                // Attempt to fit the code window considering the spans and labels plus padding.
85                let padding_left = (self.term_width - (self.span_right - self.span_left)) / 5 * 2;
86                self.computed_left = self.span_left.saturating_sub(padding_left);
87                self.computed_right = self.computed_left + self.term_width;
88            } else {
89                // Mostly give up but still don't show the full line.
90                self.computed_left = self.span_left;
91                self.computed_right = self.span_right;
92            }
93        }
94    }
95
96    pub(crate) fn left(&self, line_len: usize) -> usize {
97        min(self.computed_left, line_len)
98    }
99
100    pub(crate) fn right(&self, line_len: usize) -> usize {
101        if line_len.saturating_sub(self.computed_left) <= self.term_width {
102            line_len
103        } else {
104            min(line_len, self.computed_right)
105        }
106    }
107}
annotate_snippets/renderer/margin.rs

annotate_snippets/renderer/
margin.rs
