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//! [`BoxBorder`]: a single-line box border.
use retroglyph_core::{Backend, Rect, Style, Terminal};
use super::Widget;
use crate::Theme;
use crate::draw::{BL, BR, H, TL, TR, V};
/// A single-line box border drawn around a [`Rect`].
///
/// The interior of the rectangle is not touched. `area` must be at least
/// 2×2, or [`Widget::render`] is a no-op. `style` defaults to
/// [`Style::new()`]; set it with [`BoxBorder::style`].
#[derive(Clone, Copy, Debug, Default)]
pub struct BoxBorder {
style: Style,
}
impl BoxBorder {
/// A plain box border; see [`BoxBorder::style`] to color it.
#[must_use]
pub fn new() -> Self {
Self::default()
}
/// Set the border's style.
#[must_use]
pub const fn style(mut self, style: Style) -> Self {
self.style = style;
self
}
/// Sets `style` to `theme.border` on `theme.panel_bg`.
///
/// The background is set explicitly rather than left at [`Style::new()`]'s default: an unset
/// background isn't "transparent" once a real backend draws it (a bare `Color::Default` cell
/// paints as solid black behind the glyph, not whatever was there before -- see
/// `retroglyph-software`'s `DEFAULT_BG`), which would leave a visible black grid of border
/// cells on a light [`Theme`] rather than a border blending into its surroundings. That means
/// this widget has to assume *something* about what it's drawn over, even though (unlike
/// [`super::Panel`], which also owns and fills its own interior) a standalone `BoxBorder`
/// genuinely doesn't know -- `theme.panel_bg` is the closest default, matching what a themed
/// [`super::Panel`]/[`super::Modal`] around it would use. Drawing this border directly on the
/// raw screen background instead needs a manual [`BoxBorder::style`] override afterwards.
///
/// Call before any manual [`BoxBorder::style`] override you want to keep.
#[must_use]
pub fn theme(mut self, theme: Theme) -> Self {
self.style = Style::new().fg(theme.border).bg(theme.panel_bg);
self
}
}
impl<B: Backend> Widget<B> for BoxBorder {
fn render(self, area: Rect, term: &mut Terminal<B>) {
if area.width() < 2 || area.height() < 2 {
return;
}
let x0 = area.left();
let y0 = area.top();
let x1 = area.right().saturating_sub(1);
let y1 = area.bottom().saturating_sub(1);
term.reset_style()
.fg(self.style.foreground())
.bg(self.style.background());
// Corners
term.put(x0, y0, TL);
term.put(x1, y0, TR);
term.put(x0, y1, BL);
term.put(x1, y1, BR);
// Horizontal edges
for x in (x0 + 1)..x1 {
term.put(x, y0, H);
term.put(x, y1, H);
}
// Vertical edges
for y in (y0 + 1)..y1 {
term.put(x0, y, V);
term.put(x1, y, V);
}
term.reset_style();
}
}
#[cfg(test)]
mod tests {
use retroglyph_core::{Color, Headless};
use super::*;
#[test]
fn draws_corners_and_edges() {
let area = Rect::new(0, 0, 5, 3);
let mut term = Terminal::new(Headless::new(5, 3));
BoxBorder::new()
.style(Style::new().fg(Color::WHITE))
.render(area, &mut term);
assert_eq!(term.grid().get(0, 0).glyph(), TL);
assert_eq!(term.grid().get(4, 0).glyph(), TR);
assert_eq!(term.grid().get(0, 2).glyph(), BL);
assert_eq!(term.grid().get(4, 2).glyph(), BR);
assert_eq!(term.grid().get(2, 0).glyph(), H);
assert_eq!(term.grid().get(0, 1).glyph(), V);
// Interior untouched.
assert_eq!(term.grid().get(2, 1).glyph(), ' ');
}
#[test]
fn too_small_is_a_no_op() {
let area = Rect::new(0, 0, 1, 1);
let mut term = Terminal::new(Headless::new(1, 1));
BoxBorder::new().render(area, &mut term);
assert_eq!(term.grid().get(0, 0).glyph(), ' ');
}
#[test]
fn theme_maps_border_role_onto_style() {
let area = Rect::new(0, 0, 5, 3);
let mut term = Terminal::new(Headless::new(5, 3));
BoxBorder::new().theme(Theme::DARK).render(area, &mut term);
assert_eq!(
term.grid().get(0, 0).style().foreground(),
Theme::DARK.border
);
assert_eq!(
term.grid().get(0, 0).style().background(),
Theme::DARK.panel_bg
);
}
}