feat(style): Add style with fn

[a-kenji]

This allows the full style to be constructed in a const context.

A const style can be used in the following way:

const DEFAULT_MODIFIER: Modifier = Modifier::BOLD.union(Modifier::ITALIC);
const EMPTY: Modifier = Modifier::empty();
const DEFAULT_STYLE: Style = Style::with(DEFAULT_MODIFIER, EMPTY)
.fg(Color::Red).bg(Color::Black);

[codecov]

Codecov Report

Merging #287 (41304bb) into main (56e44a0) will increase coverage by 0.04%.
The diff coverage is 88.46%.

❗ Current head 41304bb differs from pull request most recent head 6ac1500. Consider uploading reports for the commit 6ac1500 to get more accurate results

@@            Coverage Diff             @@
##             main     #287      +/-   ##
==========================================
+ Coverage   82.92%   82.97%   +0.04%     
==========================================
  Files          37       37              
  Lines        7479     7500      +21     
==========================================
+ Hits         6202     6223      +21     
  Misses       1277     1277              

Impacted Files	Coverage Δ
src/widgets/canvas/line.rs	59.67% <50.00%> (ø)
src/widgets/canvas/mod.rs	91.88% <50.00%> (ø)
src/style.rs	86.85% <100.00%> (+1.20%)	⬆️

[joshka]

I prefer not to have methods that have two parameters of the same type because anyone reading the code unfamiliar with the library will always have to look up what each parameter indicates.

However, this can done without a new method by making add/remove_modifier() const. The implementations only have to change slightly to support this as insert() / remove() on bitflags aren't const-safe:

    pub const fn add_modifier(mut self, modifier: Modifier) -> Style {
        self.sub_modifier = self.sub_modifier.difference(modifier);
        self.add_modifier = self.add_modifier.union(modifier);
        self
    }

    pub const fn remove_modifier(mut self, modifier: Modifier) -> Style {
        self.add_modifier = self.add_modifier.difference(modifier);
        self.sub_modifier = self.sub_modifier.union(modifier);
        self
    }

    #[test]
    fn style_can_be_const() {
        const _RED: Color = Color::Red;
        const _BLACK: Color = Color::Black;
        const _BOLD: Modifier = Modifier::BOLD;
        const _ITALIC: Modifier = Modifier::ITALIC;

        const _RESET: Style = Style::reset();
        const _RED_FG: Style = Style::new().fg(_RED);
        const _BLACK_BG: Style = Style::new().bg(_BLACK);
        const _ADD_BOLD: Style = Style::new().add_modifier(_BOLD);
        const _REMOVE_ITALIC: Style = Style::new().remove_modifier(_ITALIC);
        const _ALL: Style = Style::new()
            .fg(_RED)
            .bg(_BLACK)
            .add_modifier(_BOLD)
            .remove_modifier(_ITALIC);
        assert_eq!(
            _ALL,
            Style::new()
                .fg(Color::Red)
                .bg(Color::Black)
                .add_modifier(Modifier::BOLD)
                .remove_modifier(Modifier::ITALIC)
        );

[joshka]

Also - please try to give a name to the commit that indicates the user facing benefit (e.g. "make Style support const context" or something similar).

[a-kenji]

Thank you for the review, this is indeed a much better solution!

[joshka]

Rebased and approved. Thanks for this :)