feat: implement selection-first multi-target editing

src/tui.rs

@@ -242,7 +242,7 @@ fn draw(frame: &mut Frame, editor: &Editor, top: &mut usize, left: &mut usize) {
             buffer[(area.x + (column - *left) as u16, y)].set_style(style);
         }
     }
-    if let Some(selection) = editor.selection() {
+    for selection in editor.selections() {
         let first = selection.start.row.max(*top);
         let last = selection.end.row.min(top.saturating_add(height - 1));
         let style = Style::default().fg(Color::White).bg(Color::Blue);
@@ -267,6 +267,19 @@ fn draw(frame: &mut Frame, editor: &Editor, top: &mut usize, left: &mut usize) {
             }
         }
     }
+    for caret in editor.carets().into_iter().filter(|caret| *caret != cursor) {
+        if caret.row < *top || caret.row >= top.saturating_add(height) {
+            continue;
+        }
+        let column = display_column(&editor.lines()[caret.row], caret.column);
+        if column >= *left && column < left.saturating_add(width) {
+            frame.buffer_mut()[(
+                area.x + (column - *left) as u16,
+                area.y + (caret.row - *top) as u16,
+            )]
+                .set_style(Style::default().fg(Color::Black).bg(Color::Magenta));
+        }
+    }
     let path = editor
         .path()
         .map(|p| p.to_string_lossy().into_owned())
@@ -276,12 +289,17 @@ fn draw(frame: &mut Frame, editor: &Editor, top: &mut usize, left: &mut usize) {
         .map(|c| if c.is_control() { '�' } else { c })
         .collect();
     let status = format!(
-        " {}  {}{}  {}:{}",
+        " {}  {}{}  {}:{}{}",
         editor.mode(),
         path,
         if editor.dirty() { " [+]" } else { "" },
         cursor.row + 1,
-        cursor.column + 1
+        cursor.column + 1,
+        if editor.selection_count() > 1 {
+            format!("  {} selections", editor.selection_count())
+        } else {
+            String::new()
+        }
     );
     frame.render_widget(
         Paragraph::new(status).style(Style::default().fg(Color::Black).bg(Color::Cyan)),
@@ -326,6 +344,72 @@ mod tests {
         assert_eq!(visible_line(text, 5, 2), " e\u{301}");
     }
 
+    #[test]
+    fn selection_set_renders_all_ranges_and_counts_offscreen_targets() {
+        let mut editor = Editor::open(None, vec![]).unwrap();
+        editor
+            .apply(vec![crate::editor::Effect::Replace(
+                "界\n界\n界\n界\n界".into(),
+            )])
+            .unwrap();
+        editor.handle(Input::Home);
+        editor.handle(Input::Char('v'));
+        editor.handle(Input::Ctrl('a'));
+        assert_eq!(editor.selection_count(), 5);
+        assert_eq!(editor.selections().len(), 5);
+        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(48, 4)).unwrap();
+        let (mut top, mut left) = (0, 0);
+        terminal
+            .draw(|frame| draw(frame, &editor, &mut top, &mut left))
+            .unwrap();
+        let buffer = terminal.backend().buffer();
+        for selection in editor.selections() {
+            if selection.start.row >= top && selection.start.row < top + 2 {
+                let y = (selection.start.row - top) as u16;
+                assert!(matches!(buffer[(0, y)].bg, Color::Blue | Color::Magenta));
+            }
+        }
+        let status: String = (0..48).map(|x| buffer[(x, 2)].symbol()).collect();
+        assert!(status.contains("5 selections"), "{status}");
+        assert_eq!(
+            terminal.get_cursor_position().unwrap(),
+            ratatui::layout::Position::new(0, (editor.cursor().row - top) as u16)
+        );
+    }
+
+    #[test]
+    fn secondary_carets_render_on_empty_lines_and_at_line_end() {
+        let mut editor = Editor::open(None, vec![]).unwrap();
+        editor
+            .apply(vec![crate::editor::Effect::Replace("a\n\n界".into())])
+            .unwrap();
+        editor.handle(Input::Home);
+        editor.handle(Input::Ctrl('e'));
+        editor.handle(Input::Ctrl('e'));
+        assert_eq!(editor.selection_count(), 3);
+        editor.handle(Input::Char('A'));
+        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(48, 5)).unwrap();
+        let (mut top, mut left) = (0, 0);
+        terminal
+            .draw(|frame| draw(frame, &editor, &mut top, &mut left))
+            .unwrap();
+        let buffer = terminal.backend().buffer();
+        for caret in editor.carets() {
+            let x = display_column(&editor.lines()[caret.row], caret.column) as u16;
+            assert_eq!(buffer[(x, caret.row as u16)].symbol(), " ");
+            if caret != editor.cursor() {
+                assert_eq!(buffer[(x, caret.row as u16)].bg, Color::Magenta);
+            }
+        }
+        assert_eq!(
+            terminal.get_cursor_position().unwrap(),
+            ratatui::layout::Position::new(
+                display_column(&editor.lines()[editor.cursor().row], editor.cursor().column) as u16,
+                editor.cursor().row as u16
+            )
+        );
+    }
+
     #[test]
     fn visual_selection_highlights_graphemes_newlines_and_clipped_ranges_over_search() {
         let mut editor = Editor::open(None, vec![]).unwrap();