Alternative font to highlight differences

[sanmai-NL]

pretty-assertions presents differences between characters by also making differing characters boldface (1), whereas colored_diff::PrettyDifference changes the background color behind those characters (2). The former is more readable and its readability is far less dependent on terminal color scheme.

My proposal is to implement presentation 1 in colored_diff::PrettyDifference.

[CAD97]

Current styles:

colored-diff/src/lib.rs

Lines 10 to 21 in 42ba173

	fn red(s: &str) -> ANSIGenericString<str> {
	Colour::Red.paint(s)
	}
	fn on_red(s: &str) -> ANSIGenericString<str> {
	Colour::White.on(Colour::Red).bold().paint(s)
	}
	fn green(s: &str) -> ANSIGenericString<str> {
	Colour::Green.paint(s)
	}
	fn on_green(s: &str) -> ANSIGenericString<str> {
	Colour::White.on(Colour::Green).bold().paint(s)
	}

pretty-assertions uses the following (extracted from https://github.com/colin-kiegel/rust-pretty-assertions/blob/965f11b5b56a03a9c7d2d4844b5afdfc8a956f03/src/format_changeset.rs):

fn red(s: &str) -> ANSIString {
    Colour::Red.paint(s)
}
fn on_red(s: &str) -> ANSIString {
    Colour::Red.on(Colour::Fixed(52)).bold().paint(s)
}
fn green(s: &str) -> ANSIString {
    Colour::Green.paint(s)
}
fn on_green(s: &str) -> ANSIString {
    Colour::Green.on(Colour::Fixed(22)).bold().paint(s)
}

I'm not sure what the reason is, but, in my IDE's embedded terminal, I get the following output:

White.on(Red)/White.on(Green):

Red.on(52)/Green.on(22):

Thus why I likely chose this styling. For completeness, the difference example uses (the equivalent of) White.on(Green).

If I'm not mistaken, you're asking for the following styling, which is not what the current version of pretty-differences uses:

fn red(s: &str) -> ANSIGenericString<str> {
    Colour::Red.paint(s)
}
fn on_red(s: &str) -> ANSIGenericString<str> {
    Colour::Red.bold().paint(s)
}
fn green(s: &str) -> ANSIGenericString<str> {
    Colour::Green.paint(s)
}
fn on_green(s: &str) -> ANSIGenericString<str> {
    Colour::Green.bold().paint(s)
}

which looks like this in my IDE terminal:

If ansi_term uses the coming minimal const fn support of Rust to make manipulating Colour/Style const, I'll probably add a generic parameter to specify a styling set for a difference. Until then, I'm not sure what much I can do different to work ideally on more terminals.