egui-elements 1.0.30

//! Helpers: theme switcher, HSLA colors, and interactive frames.

use crate::theme::*;
use crate::visuals::FrameVisuals;
use crate::widgets::{ComboBox, Label};
use egui::{Color32, Frame, Response, RichText, Sense, Stroke, Ui};

/// Should work for most images that are shown on a very dark background
pub const TINT_1: Color32 = Color32::from_rgba_premultiplied(216, 216, 216, 255);

/// HSLA color used by the theme editor (hue 0..=360, s/l 0..=100, a 0..=1).
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
#[derive(Debug, Clone, Copy)]
pub struct Hsla {
   /// Hue 0.0..=360.0
   pub h: f32,
   /// Saturation 0.0..=100.0
   pub s: f32,
   /// Lightness 0.0..=100.0
   pub l: f32,
   /// Alpha 0.0..=1.0
   pub a: f32,
}

impl Hsla {
   /// Convert a premultiplied [`Color32`] to unpremultiplied HSLA.
   pub fn from_color32(c: Color32) -> Self {
      let (r, g, b) = unpremultiply_srgb(c);
      let (h, s, l) = srgb_to_hsl(r, g, b);
      Hsla {
         h,
         s: s * 100.0,
         l: l * 100.0,
         a: c.a() as f32 / 255.0,
      }
   }

   /// Parse `#RGB`, `#RRGGBB`, or `#RRGGBBAA`.
   pub fn from_hex(hex: &str) -> Option<Self> {
      match Color32::from_hex(hex) {
         Ok(c) => Some(Self::from_color32(c)),
         Err(_) => None,
      }
   }

   /// Convert back to a premultiplied [`Color32`].
   pub fn to_color32(&self) -> Color32 {
      let (r, g, b, a) = self.to_rgba_components();
      Color32::from_rgba_unmultiplied(r, g, b, a)
   }

   /// Unpremultiplied `(r, g, b, a)` in 0..=255.
   pub fn to_rgba_components(&self) -> (u8, u8, u8, u8) {
      let (r, g, b) = hsl_to_srgb(self.h, self.s / 100.0, self.l / 100.0);
      (
         channel_to_u8(r),
         channel_to_u8(g),
         channel_to_u8(b),
         channel_to_u8(self.a),
      )
   }

   /// Walk lightness in 5% steps, including `self` as the first entry.
   pub fn shades(&self, num_shades: usize, direction: ShadeDirection) -> Vec<Color32> {
      let mut shades = Vec::new();
      let step = if direction == ShadeDirection::Lighter {
         5.0
      } else {
         -5.0
      };
      let mut current = *self;
      for _ in 0..num_shades {
         shades.push(current.to_color32());
         current.l = (current.l as f32 + step).clamp(0.0, 100.0);
      }
      shades
   }
}

/// Direction for [`Hsla::shades`].
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
pub enum ShadeDirection {
   /// Increase lightness.
   Lighter,
   /// Decrease lightness.
   Darker,
}

/// `Color32` stores premultiplied sRGB. HSL is computed in unpremultiplied space.
fn unpremultiply_srgb(c: Color32) -> (f32, f32, f32) {
   let a = c.a();
   if a == 0 {
      (0.0, 0.0, 0.0)
   } else if a == 255 {
      (
         c.r() as f32 / 255.0,
         c.g() as f32 / 255.0,
         c.b() as f32 / 255.0,
      )
   } else {
      let a = a as f32;
      (
         c.r() as f32 / a,
         c.g() as f32 / a,
         c.b() as f32 / a,
      )
   }
}

/// Gamma-encoded sRGB → HSL (CSS / Wikipedia). `s` and `l` in 0..=1, `h` in 0..360.
fn srgb_to_hsl(r: f32, g: f32, b: f32) -> (f32, f32, f32) {
   let max = r.max(g).max(b);
   let min = r.min(g).min(b);
   let l = (max + min) * 0.5;
   let d = max - min;

   if d == 0.0 {
      return (0.0, 0.0, l);
   }

   let s = d / (1.0 - (2.0 * l - 1.0).abs());
   let h = if max == r {
      (g - b) / d
   } else if max == g {
      (b - r) / d + 2.0
   } else {
      (r - g) / d + 4.0
   };
   (h.rem_euclid(6.0) * 60.0, s, l)
}

/// HSL → gamma-encoded sRGB. `h` in degrees, `s` and `l` in 0..=1.
fn hsl_to_srgb(h: f32, s: f32, l: f32) -> (f32, f32, f32) {
   let s = s.clamp(0.0, 1.0);
   let l = l.clamp(0.0, 1.0);
   let c = (1.0 - (2.0 * l - 1.0).abs()) * s;
   let hp = h.rem_euclid(360.0) / 60.0;
   let x = c * (1.0 - (hp.rem_euclid(2.0) - 1.0).abs());
   let m = l - c * 0.5;
   let (r, g, b) = match hp as u8 {
      0 => (c, x, 0.0),
      1 => (x, c, 0.0),
      2 => (0.0, c, x),
      3 => (0.0, x, c),
      4 => (x, 0.0, c),
      _ => (c, 0.0, x),
   };
   (r + m, g + m, b + m)
}

fn channel_to_u8(channel: f32) -> u8 {
   (channel.clamp(0.0, 1.0) * 255.0) as u8
}

/// `true` if any frame-related palette slot changed.
pub fn frame_palette_changed(old: &ThemeColors, new: &ThemeColors) -> bool {
   old.title_bar != new.title_bar
      || old.bg != new.bg
      || old.widget_bg != new.widget_bg
      || old.hover != new.hover
      || old.highlight != new.highlight
      || old.border != new.border
}

/// Write `new` into `slot` only if it still equals `old`.
pub fn remap_if_eq(slot: &mut Color32, old: Color32, new: Color32) {
   if *slot == old {
      *slot = new;
   }
}

/// Remap fill, stroke, and shadow colors on an [`egui::Frame`] when they
/// still match the previous palette.
pub fn remap_frame(
   frame: &mut Frame,
   old_fill: Color32,
   new_fill: Color32,
   old_border: Color32,
   new_border: Color32,
) {
   remap_if_eq(&mut frame.fill, old_fill, new_fill);
   remap_if_eq(&mut frame.stroke.color, old_border, new_border);
   remap_if_eq(&mut frame.shadow.color, old_border, new_border);
}

/// Remap hover/click fills on [`FrameVisuals`] when they still match the
/// previous palette.
pub fn remap_frame_visuals(
   visuals: &mut FrameVisuals,
   old_hover: Color32,
   new_hover: Color32,
   old_click: Color32,
   new_click: Color32,
   old_highlight: Color32,
   new_highlight: Color32,
) {
   remap_if_eq(&mut visuals.bg_on_hover, old_hover, new_hover);
   remap_if_eq(&mut visuals.bg_on_click, old_click, new_click);
   remap_if_eq(
      &mut visuals.border_on_hover.1,
      old_highlight,
      new_highlight,
   );
   remap_if_eq(
      &mut visuals.border_on_click.1,
      old_highlight,
      new_highlight,
   );
}

/// Show a ComboBox to change the theme
///
/// Returns the new theme if we select one, the new theme is installed to the [egui::Context]
pub fn theme_switcher(current_theme: &Theme, ui: &mut Ui) -> Option<Theme> {
   let mut new_theme_opt = None;

   let text = RichText::new(current_theme.kind.to_str()).size(current_theme.typography.normal);
   let current = Label::new(text, None);

   ComboBox::new("Theme switcher", current).width(200.0).show_ui(ui, |ui| {
      ui.spacing_mut().item_spacing.y = 12.0;

      for kind in ThemeKind::to_vec() {
         let label = RichText::new(kind.to_str()).size(current_theme.typography.normal);
         let label = Label::new(label, None)
            .interactive(true)
            .fill_width(true)
            .sense(Sense::click())
            .expand(Some(4.0));

         if ui.add(label).clicked() {
            let mut new_theme = Theme::new(kind);
            new_theme_opt = Some(new_theme.clone());
            new_theme.install(ui.ctx());
         }
      }
   });
   new_theme_opt
}

/// Paint `frame` with hover/click fills from `visuals`.
///
/// The closure runs inside the frame. Returns the inner content response.
pub fn frame(
   frame: &mut Frame,
   visuals: FrameVisuals,
   ui: &mut Ui,
   add_contents: impl FnOnce(&mut Ui),
) -> Response {
   let mut frame = frame.begin(ui);
   let res = frame.content_ui.scope(|ui| add_contents(ui));

   if res.response.interact(Sense::click()).clicked() {
      frame.frame = frame.frame.fill(visuals.bg_on_click);
      frame.frame = frame.frame.stroke(Stroke::new(
         visuals.border_on_click.0,
         visuals.border_on_click.1,
      ));
   } else if res.response.hovered() {
      frame.frame = frame.frame.fill(visuals.bg_on_hover);
      frame.frame = frame.frame.stroke(Stroke::new(
         visuals.border_on_hover.0,
         visuals.border_on_hover.1,
      ));
   }

   frame.end(ui);
   res.response
}

#[cfg(test)]
mod tests {
   use super::*;

   fn assert_near_color(a: Color32, b: Color32) {
      let dr = (a.r() as i16 - b.r() as i16).abs();
      let dg = (a.g() as i16 - b.g() as i16).abs();
      let db = (a.b() as i16 - b.b() as i16).abs();
      assert!(
         dr <= 1 && dg <= 1 && db <= 1 && a.a() == b.a(),
         "roundtrip {a:?} -> {b:?}"
      );
   }

   #[test]
   fn color32_hsla_roundtrip() {
      let samples = [
         Color32::from_rgba_unmultiplied(0, 0, 0, 255),
         Color32::from_rgba_unmultiplied(255, 255, 255, 255),
         Color32::from_rgba_unmultiplied(255, 0, 0, 255),
         Color32::from_rgba_unmultiplied(0, 255, 0, 255),
         Color32::from_rgba_unmultiplied(0, 0, 255, 255),
         Color32::from_rgba_unmultiplied(128, 64, 192, 128),
         Color32::from_rgba_unmultiplied(26, 27, 38, 255),
         Color32::from_rgba_unmultiplied(122, 162, 247, 200),
      ];
      for c in samples {
         assert_near_color(c, Hsla::from_color32(c).to_color32());
      }
   }

   #[test]
   fn from_hex_parses_and_preserves_alpha() {
      let hsla = Hsla::from_hex("#7aa2f7").unwrap();
      let (r, g, b, a) = hsla.to_rgba_components();
      assert_eq!((r, g, b, a), (122, 162, 247, 255));

      let hsla = Hsla::from_hex("#7aa2f780").unwrap();
      assert!((hsla.a - 128.0 / 255.0).abs() < 1e-5);
      assert_eq!(hsla.to_color32().a(), 128);
   }

   #[test]
   fn hsl_pure_red() {
      let c = Hsla {
         h: 0.0,
         s: 100.0,
         l: 50.0,
         a: 1.0,
      }
      .to_color32();
      assert_eq!(c, Color32::from_rgb(255, 0, 0));
   }
}