list_item: trailing icon slot and horizontal inset override

Disclosure arrows in list rows could only be text: the trailing slot draws a string, so apps fell back to the "›" glyph at 14 px, which cannot use the theme's arrow SVGs and looks thin next to 24 px leading icons. Add ListItem::trailing_icon( rgba, w, h ): a right-aligned icon drawn at the new theme::TRAILING_ICON_SIZE (21 px, 1.5x the old glyph em box), vertically centered. It coexists with trailing text, which shifts to the icon's left. Like the leading icon, symbolic assets are pre-tinted by the caller (tint_symbolic), so the widget stays colour-agnostic.
Add ListItem::pad_h( impl Into<Length> ), a per-item override of the horizontal inset between the row edge and its content (leading icon/label on the left, trailing text/icon on the right). Resolution follows the Separator pattern: an explicit Length wins, otherwise the theme default (16 px through geom_px) applies, so existing rows are unaffected. This lets an app whose enclosing view already provides the margin bring row content flush instead of stacking both insets.
Document both builders in docs/widgets.md and the changelog, and rework the list_item rustdoc example to point at trailing_icon with a theme icon for disclosure arrows instead of the text glyph.

src/widget/list_item/mod.rs

@@ -3,7 +3,7 @@
 
 use std::sync::Arc;
 
-use crate::types::{ Rect, WidgetId };
+use crate::types::{ Length, Rect, WidgetId };
 use crate::render::Canvas;
 use super::Element;
 
@@ -42,9 +42,14 @@ pub struct ListItem<Msg: Clone>
 	/// Optional secondary line drawn below the label in muted colour.
 	/// Doubles the row height when set.
 	pub( crate ) subtitle: Option<String>,
-	/// Optional right-aligned text (current setting, badge count, "›"
-	/// disclosure). Drawn in muted colour.
+	/// Optional right-aligned text (current setting, badge count).
+	/// Drawn in muted colour.
 	pub( crate ) trailing: Option<String>,
+	/// Optional right-aligned icon — RGBA bytes + native dimensions.
+	/// Drawn at `theme::TRAILING_ICON_SIZE`, to the right of the
+	/// trailing text when both are set. Symbolic icons should be
+	/// pre-tinted by the caller (see [`crate::tint_symbolic`]).
+	pub( crate ) trailing_icon: Option<( Arc<Vec<u8>>, u32, u32 )>,
 	/// Message emitted on tap. `None` keeps the item visible but inert.
 	pub( crate ) on_press: Option<Msg>,
 	/// Optional stable identifier for focus management.
@@ -59,6 +64,9 @@ pub struct ListItem<Msg: Clone>
 	/// when this is set, and offsets the label / subtitle by the
 	/// same amount. Pass `None` to keep the icon-less layout.
 	pub( crate ) icon: Option<( Arc<Vec<u8>>, u32, u32 )>,
+	/// Optional override of the horizontal content inset. `None`
+	/// falls back to `theme::PAD_H`.
+	pub( crate ) pad_h: Option<Length>,
 }
 
 impl<Msg: Clone> ListItem<Msg>
@@ -69,13 +77,15 @@ impl<Msg: Clone> ListItem<Msg>
 	{
 		Self
 		{
-			label:    label.into(),
-			subtitle: None,
-			trailing: None,
-			on_press: None,
-			id:       None,
-			selected: false,
-			icon:     None,
+			label:         label.into(),
+			subtitle:      None,
+			trailing:      None,
+			trailing_icon: None,
+			on_press:      None,
+			id:            None,
+			selected:      false,
+			icon:          None,
+			pad_h:         None,
 		}
 	}
 
@@ -114,6 +124,25 @@ impl<Msg: Clone> ListItem<Msg>
 		self
 	}
 
+	/// Attach a right-aligned icon (disclosure arrow). Pass the decoded
+	/// RGBA buffer alongside the image's native width and height; the
+	/// draw path scales it down to `theme::TRAILING_ICON_SIZE`.
+	pub fn trailing_icon( mut self, rgba: Arc<Vec<u8>>, w: u32, h: u32 ) -> Self
+	{
+		self.trailing_icon = Some( ( rgba, w, h ) );
+		self
+	}
+
+	/// Override the horizontal inset between the row edge and its
+	/// content (leading icon / label on the left, trailing text or
+	/// icon on the right). Accepts logical `f32` pixels or any
+	/// [`Length`]; without this it uses the theme default.
+	pub fn pad_h( mut self, p: impl Into<Length> ) -> Self
+	{
+		self.pad_h = Some( p.into() );
+		self
+	}
+
 	/// Set the message emitted when the row is tapped.
 	pub fn on_press( mut self, msg: Msg ) -> Self
 	{
@@ -178,7 +207,9 @@ impl<Msg: Clone> ListItem<Msg>
 		}
 
 		let label_size = canvas.font_px( theme::LABEL_SIZE );
-		let pad_h      = canvas.geom_px( theme::PAD_H );
+		let pad_h      = self.pad_h
+			.map( |l| l.resolve( canvas.viewport_layout(), Length::EM_BASE_DEFAULT ) )
+			.unwrap_or_else( || canvas.geom_px( theme::PAD_H ) );
 		let has_sub  = self.subtitle.is_some();
 		let label_y  = if has_sub
 		{
@@ -215,11 +246,27 @@ impl<Msg: Clone> ListItem<Msg>
 			canvas.draw_text( sub, text_x, sub_y, sub_size, subtitle_color );
 		}
 
+		let mut trail_right = rect.x + rect.width - pad_h;
+
+		if let Some( ( rgba, w, h ) ) = &self.trailing_icon
+		{
+			let icon_size = canvas.geom_px( theme::TRAILING_ICON_SIZE );
+			let icon_rect = Rect
+			{
+				x:      trail_right - icon_size,
+				y:      rect.y + ( rect.height - icon_size ) / 2.0,
+				width:  icon_size,
+				height: icon_size,
+			};
+			canvas.draw_image_data( rgba, *w, *h, icon_rect, 1.0 );
+			trail_right = icon_rect.x - canvas.geom_px( theme::ICON_GAP );
+		}
+
 		if let Some( ref trail ) = self.trailing
 		{
 			let trail_size = canvas.font_px( theme::TRAILING_SIZE );
 			let tw = canvas.measure_text( trail, trail_size );
-			let tx = rect.x + rect.width - pad_h - tw;
+			let tx = trail_right - tw;
 			let ty = rect.y + ( rect.height + trail_size ) / 2.0 - 2.0;
 			canvas.draw_text( trail, tx, ty, trail_size, trailing_color );
 		}
@@ -232,20 +279,24 @@ impl<Msg: Clone> ListItem<Msg>
 	{
 		ListItem
 		{
-			label:    self.label,
-			subtitle: self.subtitle,
-			trailing: self.trailing,
-			on_press: self.on_press.map( |m| ( *f )( m ) ),
-			id:       self.id,
-			selected: self.selected,
-			icon:     self.icon,
+			label:         self.label,
+			subtitle:      self.subtitle,
+			trailing:      self.trailing,
+			trailing_icon: self.trailing_icon,
+			on_press:      self.on_press.map( |m| ( *f )( m ) ),
+			id:            self.id,
+			selected:      self.selected,
+			icon:          self.icon,
+			pad_h:         self.pad_h,
 		}
 	}
 }
 
 /// Create a [`ListItem`] with the given primary label.
 ///
-/// Add detail and behaviour through the chained builders:
+/// Add detail and behaviour through the chained builders. For a
+/// disclosure arrow use [`ListItem::trailing_icon`] with a theme icon
+/// (e.g. `"general/right"`) rather than a text glyph:
 ///
 /// ```rust,no_run
 /// # use ltk::{ list_item, ListItem };
@@ -253,7 +304,7 @@ impl<Msg: Clone> ListItem<Msg>
 /// # fn _ex() -> ListItem<Msg> {
 /// list_item( "Display" )
 ///     .subtitle( "Resolution, brightness, night mode" )
-///     .trailing( "›" )
+///     .trailing( "Light" )
 ///     .on_press( Msg::OpenDisplay )
 /// # }
 /// ```

src/widget/list_item/theme.rs

@@ -33,5 +33,7 @@ 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;
+/// Visible side of the optional trailing icon (square).
+pub const TRAILING_ICON_SIZE: f32 = 21.0;
 /// Gap between the leading icon's right edge and the label baseline.
 pub const ICON_GAP:      f32 = 12.0;