nu_ansi_term/
difference.rs

1use super::Style;
2
3/// When printing out one colored string followed by another, use one of
4/// these rules to figure out which *extra* control codes need to be sent.
5#[derive(PartialEq, Clone, Copy, Debug)]
6pub enum Difference {
7    /// Print out the control codes specified by this style to end up looking
8    /// like the second string's styles.
9    ExtraStyles(Style),
10
11    /// Converting between these two is impossible, so just send a reset
12    /// command and then the second string's styles.
13    Reset,
14
15    /// The before style is exactly the same as the after style, so no further
16    /// control codes need to be printed.
17    Empty,
18}
19
20impl Difference {
21    /// Compute the 'style difference' required to turn an existing style into
22    /// the given, second style.
23    ///
24    /// For example, to turn green text into green bold text, it's redundant
25    /// to write a reset command then a second green+bold command, instead of
26    /// just writing one bold command. This method should see that both styles
27    /// use the foreground color green, and reduce it to a single command.
28    ///
29    /// This method returns an enum value because it's not actually always
30    /// possible to turn one style into another: for example, text could be
31    /// made bold and underlined, but you can't remove the bold property
32    /// without also removing the underline property. So when this has to
33    /// happen, this function returns None, meaning that the entire set of
34    /// styles should be reset and begun again.
35    pub fn between(first: &Style, next: &Style) -> Difference {
36        use self::Difference::*;
37
38        // XXX(Havvy): This algorithm is kind of hard to replicate without
39        // having the Plain/Foreground enum variants, so I'm just leaving
40        // it commented out for now, and defaulting to Reset.
41
42        if first == next {
43            return Empty;
44        }
45
46        // Cannot un-bold, so must Reset.
47        if first.is_bold && !next.is_bold {
48            return Reset;
49        }
50
51        if first.is_dimmed && !next.is_dimmed {
52            return Reset;
53        }
54
55        if first.is_italic && !next.is_italic {
56            return Reset;
57        }
58
59        // Cannot un-underline, so must Reset.
60        if first.is_underline && !next.is_underline {
61            return Reset;
62        }
63
64        if first.is_blink && !next.is_blink {
65            return Reset;
66        }
67
68        if first.is_reverse && !next.is_reverse {
69            return Reset;
70        }
71
72        if first.is_hidden && !next.is_hidden {
73            return Reset;
74        }
75
76        if first.is_strikethrough && !next.is_strikethrough {
77            return Reset;
78        }
79
80        // Cannot go from foreground to no foreground, so must Reset.
81        if first.foreground.is_some() && next.foreground.is_none() {
82            return Reset;
83        }
84
85        // Cannot go from background to no background, so must Reset.
86        if first.background.is_some() && next.background.is_none() {
87            return Reset;
88        }
89
90        let mut extra_styles = Style::default();
91
92        if first.is_bold != next.is_bold {
93            extra_styles.is_bold = true;
94        }
95
96        if first.is_dimmed != next.is_dimmed {
97            extra_styles.is_dimmed = true;
98        }
99
100        if first.is_italic != next.is_italic {
101            extra_styles.is_italic = true;
102        }
103
104        if first.is_underline != next.is_underline {
105            extra_styles.is_underline = true;
106        }
107
108        if first.is_blink != next.is_blink {
109            extra_styles.is_blink = true;
110        }
111
112        if first.is_reverse != next.is_reverse {
113            extra_styles.is_reverse = true;
114        }
115
116        if first.is_hidden != next.is_hidden {
117            extra_styles.is_hidden = true;
118        }
119
120        if first.is_strikethrough != next.is_strikethrough {
121            extra_styles.is_strikethrough = true;
122        }
123
124        if first.foreground != next.foreground {
125            extra_styles.foreground = next.foreground;
126        }
127
128        if first.background != next.background {
129            extra_styles.background = next.background;
130        }
131
132        ExtraStyles(extra_styles)
133    }
134}
135
136#[cfg(test)]
137mod test {
138    use super::Difference::*;
139    use super::*;
140    use crate::style::Color::*;
141    use crate::style::Style;
142
143    fn style() -> Style {
144        Style::new()
145    }
146
147    macro_rules! test {
148        ($name: ident: $first: expr; $next: expr => $result: expr) => {
149            #[test]
150            fn $name() {
151                assert_eq!($result, Difference::between(&$first, &$next));
152            }
153        };
154    }
155
156    test!(nothing:    Green.normal(); Green.normal()  => Empty);
157    test!(uppercase:  Green.normal(); Green.bold()    => ExtraStyles(style().bold()));
158    test!(lowercase:  Green.bold();   Green.normal()  => Reset);
159    test!(nothing2:   Green.bold();   Green.bold()    => Empty);
160
161    test!(color_change: Red.normal(); Blue.normal() => ExtraStyles(Blue.normal()));
162
163    test!(addition_of_blink:          style(); style().blink()          => ExtraStyles(style().blink()));
164    test!(addition_of_dimmed:         style(); style().dimmed()         => ExtraStyles(style().dimmed()));
165    test!(addition_of_hidden:         style(); style().hidden()         => ExtraStyles(style().hidden()));
166    test!(addition_of_reverse:        style(); style().reverse()        => ExtraStyles(style().reverse()));
167    test!(addition_of_strikethrough:  style(); style().strikethrough()  => ExtraStyles(style().strikethrough()));
168
169    test!(removal_of_strikethrough:   style().strikethrough(); style()  => Reset);
170    test!(removal_of_reverse:         style().reverse();       style()  => Reset);
171    test!(removal_of_hidden:          style().hidden();        style()  => Reset);
172    test!(removal_of_dimmed:          style().dimmed();        style()  => Reset);
173    test!(removal_of_blink:           style().blink();         style()  => Reset);
174}
nu_ansi_term/difference.rs

nu_ansi_term/
difference.rs
