1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use utils::make_indent;
13 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
17 // All items on one row.
19 // Try Horizontal layout, if that fails then vertical
21 // Pack as many items as possible per row over (possibly) many rows.
25 #[derive(Eq, PartialEq, Debug, Copy, Clone)]
26 pub enum SeparatorTactic {
32 // TODO having some helpful ctors for ListFormatting would be nice.
33 pub struct ListFormatting<'a> {
34 pub tactic: ListTactic,
35 pub separator: &'a str,
36 pub trailing_separator: SeparatorTactic,
38 // Available width if we layout horizontally.
40 // Available width if we layout vertically
44 // Format a list of strings into a string.
45 // Precondition: all strings in items are trimmed.
46 pub fn write_list<'b>(items: &[(String, String)], formatting: &ListFormatting<'b>) -> String {
51 let mut tactic = formatting.tactic;
53 // Conservatively overestimates because of the changing separator tactic.
54 let sep_count = if formatting.trailing_separator != SeparatorTactic::Never {
59 let sep_len = formatting.separator.len();
60 let total_sep_len = (sep_len + 1) * sep_count;
62 let total_width = calculate_width(items);
64 // Check if we need to fallback from horizontal listing, if possible.
65 if tactic == ListTactic::HorizontalVertical {
66 if total_width + total_sep_len > formatting.h_width {
67 tactic = ListTactic::Vertical;
69 tactic = ListTactic::Horizontal;
73 // Now that we know how we will layout, we can decide for sure if there
74 // will be a trailing separator.
75 let trailing_separator = needs_trailing_separator(formatting.trailing_separator, tactic);
77 // Create a buffer for the result.
78 // TODO could use a StringBuffer or rope for this
79 let alloc_width = if tactic == ListTactic::Horizontal {
80 total_width + total_sep_len
82 total_width + items.len() * (formatting.indent + 1)
84 let mut result = String::with_capacity(alloc_width);
87 let indent_str = &make_indent(formatting.indent);
88 for (i, &(ref item, ref comment)) in items.iter().enumerate() {
90 let separate = i != items.len() - 1 || trailing_separator;
93 ListTactic::Horizontal if !first => {
96 ListTactic::Vertical if !first => {
98 result.push_str(indent_str);
100 ListTactic::Mixed => {
101 let mut item_width = item.len();
103 item_width += sep_len;
106 if line_len > 0 && line_len + item_width > formatting.v_width {
108 result.push_str(indent_str);
117 line_len += item_width;
122 result.push_str(item);
124 if tactic != ListTactic::Vertical && comment.len() > 0 {
126 result.push_str(comment);
130 result.push_str(formatting.separator);
133 if tactic == ListTactic::Vertical && comment.len() > 0 {
135 result.push_str(comment);
142 fn needs_trailing_separator(separator_tactic: SeparatorTactic, list_tactic: ListTactic) -> bool {
143 match separator_tactic {
144 SeparatorTactic::Always => true,
145 SeparatorTactic::Vertical => list_tactic == ListTactic::Vertical,
146 SeparatorTactic::Never => false,
150 fn calculate_width(items:&[(String, String)]) -> usize {
151 let missed_width = items.iter().map(|&(_, ref s)| {
152 let text_len = s.trim().len();
154 // We'll put a space before any comment.
159 }).fold(0, |a, l| a + l);
160 let item_width = items.iter().map(|&(ref s, _)| s.len()).fold(0, |a, l| a + l);
161 missed_width + item_width