Add option to repeat list highlight symbol

When this option is true, the hightlight symbol is repeated for each
line of the selected item, instead of just the first line.

src/widgets/list.rs

@@ -87,6 +87,8 @@ pub struct List<'a> {
     highlight_style: Style,
     /// Symbol in front of the selected item (Shift all items to the right)
     highlight_symbol: Option<&'a str>,
+    /// Whether to repeat the highlight symbol for each line of the selected item
+    repeat_highlight_symbol: bool,
 }
 
 impl<'a> List<'a> {
@@ -101,6 +103,7 @@ impl<'a> List<'a> {
             start_corner: Corner::TopLeft,
             highlight_style: Style::default(),
             highlight_symbol: None,
+            repeat_highlight_symbol: false,
         }
     }
 
@@ -123,6 +126,11 @@ impl<'a> List<'a> {
         self.highlight_style = style;
         self
     }
+    
+    pub fn repeat_highlight_symbol(mut self, repeat: bool) -> List<'a> {
+        self.repeat_highlight_symbol = repeat;
+        self
+    }
 
     pub fn start_corner(mut self, corner: Corner) -> List<'a> {
         self.start_corner = corner;
@@ -227,19 +235,21 @@ impl<'a> StatefulWidget for List<'a> {
             buf.set_style(area, item_style);
 
             let is_selected = state.selected.map(|s| s == i).unwrap_or(false);
-            let elem_x = if has_selection {
-                let symbol = if is_selected {
+            for (j, line) in item.content.lines.iter().enumerate() {
+                // if the item is selected, we need to display the hightlight symbol:
+                // - either for the first line of the item only,
+                // - or for each line of the item if the appropriate option is set
+                let symbol = if is_selected && (j == 0 || self.repeat_highlight_symbol){
                     highlight_symbol
                 } else {
                     &blank_symbol
                 };
-                let (x, _) = buf.set_stringn(x, y, symbol, list_area.width as usize, item_style);
-                x
-            } else {
-                x
-            };
-            let max_element_width = (list_area.width - (elem_x - x)) as usize;
-            for (j, line) in item.content.lines.iter().enumerate() {
+                let (elem_x, max_element_width) = if has_selection {
+                    let (elem_x, _) = buf.set_stringn(x, y + j as u16, symbol, list_area.width as usize, item_style);
+                    (elem_x, (list_area.width - (elem_x - x)) as u16)
+                } else {
+                    (x, list_area.width)
+                };
                 buf.set_spans(elem_x, y + j as u16, line, max_element_width as u16);
             }
             if is_selected {