list_item: optional leading icon

Add a leading-icon slot to ListItem so settings-style rows can pair
a 24 px symbolic glyph with the label. `.icon( rgba, w, h )` takes
the same shape the rest of the toolkit uses for raw pixmaps; the
draw path reserves `ICON_SIZE + ICON_GAP` on the left and shifts
the label / subtitle text origin so existing icon-less rows render
unchanged.

src/widget/list_item/mod.rs

@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: LGPL-2.1-only
 // Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>
 
+use std::sync::Arc;
+
 use crate::types::{ Rect, WidgetId };
 use crate::render::Canvas;
 use super::Element;
@@ -49,9 +51,14 @@ pub struct ListItem<Msg: Clone>
 	pub id:       Option<WidgetId>,
 	/// `true` paints the row with the dark selected surface and white
 	/// text, regardless of hover / press state. Use to indicate the
-	/// active item in a list of choices (combo dropdown, segmented
-	/// picker, settings group with a single active value).
+	/// active item in a list of choices (combo dropdown, settings
+	/// group with a single active value).
 	pub selected: bool,
+	/// Optional leading icon — RGBA bytes + native dimensions. The
+	/// row reserves `theme::ICON_SIZE + theme::ICON_GAP` on the left
+	/// when this is set, and offsets the label / subtitle by the
+	/// same amount. Pass `None` to keep the icon-less layout.
+	pub icon: Option<( Arc<Vec<u8>>, u32, u32 )>,
 }
 
 impl<Msg: Clone> ListItem<Msg>
@@ -68,9 +75,21 @@ impl<Msg: Clone> ListItem<Msg>
 			on_press: None,
 			id:       None,
 			selected: false,
+			icon:     None,
 		}
 	}
 
+	/// Attach a leading icon. Pass the decoded RGBA buffer alongside
+	/// the image's native width and height; the draw path scales it
+	/// down to [`theme::ICON_SIZE`] on the same row baseline as the
+	/// label. Symbolic icons should be pre-tinted by the caller (see
+	/// [`crate::tint_symbolic`]).
+	pub fn icon( mut self, rgba: Arc<Vec<u8>>, w: u32, h: u32 ) -> Self
+	{
+		self.icon = Some( ( rgba, w, h ) );
+		self
+	}
+
 	/// Mark this row as the currently-selected option in its list.
 	/// Selected rows paint with a dark surface and white text and
 	/// override hover / press visuals.
@@ -161,12 +180,29 @@ impl<Msg: Clone> ListItem<Msg>
 			rect.y + ( rect.height + theme::LABEL_SIZE ) / 2.0 - 2.0
 		};
 
-		canvas.draw_text( &self.label, rect.x + theme::PAD_H, label_y, theme::LABEL_SIZE, label_color );
+		// Leading-icon column shifts the text right by
+		// `ICON_SIZE + ICON_GAP`. Symbolic icons (single channel
+		// pre-tinted) draw at full opacity; the colour comes from
+		// the bytes the caller passed in, which is why the helper
+		// is in `theme::icon_rgba` rather than baked here.
+		let text_x = if let Some( ( rgba, w, h ) ) = &self.icon
+		{
+			let icon_y    = rect.y + ( rect.height - theme::ICON_SIZE ) / 2.0;
+			let icon_rect = Rect { x: rect.x + theme::PAD_H, y: icon_y, width: theme::ICON_SIZE, height: theme::ICON_SIZE };
+			canvas.draw_image_data( rgba, *w, *h, icon_rect, 1.0 );
+			rect.x + theme::PAD_H + theme::ICON_SIZE + theme::ICON_GAP
+		}
+		else
+		{
+			rect.x + theme::PAD_H
+		};
+
+		canvas.draw_text( &self.label, text_x, label_y, theme::LABEL_SIZE, label_color );
 
 		if let Some( ref sub ) = self.subtitle
 		{
 			let sub_y = rect.y + rect.height * 0.62 + theme::SUBTITLE_SIZE * 0.3;
-			canvas.draw_text( sub, rect.x + theme::PAD_H, sub_y, theme::SUBTITLE_SIZE, subtitle_color );
+			canvas.draw_text( sub, text_x, sub_y, theme::SUBTITLE_SIZE, subtitle_color );
 		}
 
 		if let Some( ref trail ) = self.trailing
@@ -191,6 +227,7 @@ impl<Msg: Clone> ListItem<Msg>
 			on_press: self.on_press.map( |m| ( *f )( m ) ),
 			id:       self.id,
 			selected: self.selected,
+			icon:     self.icon,
 		}
 	}
 }

src/widget/list_item/theme.rs

@@ -31,3 +31,7 @@ pub const HEIGHT_SUB:    f32 = 68.0;
 pub const PAD_H:         f32 = 16.0;
 pub const RADIUS:        f32 = 12.0;
 pub const FOCUS_W:       f32 = 2.0;
+/// Visible side of the optional leading icon (square).
+pub const ICON_SIZE:     f32 = 24.0;
+/// Gap between the leading icon's right edge and the label baseline.
+pub const ICON_GAP:      f32 = 12.0;