Add ability to select single/multiple line(s) by clicking the line numbers(#583)

src/tui.rs

@@ -2312,11 +2312,46 @@ impl<'a> Context<'a, '_> {
                     }
                 }
             }
+                // Clicking on the left margin (gutter) should select the whole line.
+                let margin_rect = Rect {
+                    left: inner.left,
+                    top: inner.top,
+                    right: inner.left + tb.margin_width(),
+                    bottom: inner.bottom,
+                };
 
-            self.set_input_consumed();
-            return make_cursor_visible;
-        }
+                if margin_rect.contains(self.tui.mouse_down_position) {
+                    // If the user is dragging the mouse after pressing in the margin,
+                    // update the selection to span from the initial click line to the current mouse line.
+                    if self.tui.mouse_is_drag {
+                        // Ensure there's a selection anchor at the original cursor position.
+                        if !tb.has_selection() {
+                            tb.start_selection();
+                        }
+                        let drag_pos = Point { x: 0, y: pos.y };
+                        tb.selection_update_visual(drag_pos);
+                        tc.preferred_column = tb.cursor_visual_pos().x;
+                        make_cursor_visible = true;
+                    } else {
+                        // Single click: either extend selection (Shift) or select the clicked line.
+                        let click_pos = pos;
 
+                        if self.input_mouse_modifiers.contains(kbmod::SHIFT) {
+                            tb.selection_update_visual(click_pos);
+                        } else {
+                            tb.cursor_move_to_visual(click_pos);
+                            tb.select_line();
+                        }
+
+                        tc.preferred_column = tb.cursor_visual_pos().x;
+                        make_cursor_visible = true;
+                    }
+
+                    // Consume input once and return.
+                    self.set_input_consumed();
+                    return make_cursor_visible;
+                }
+            }
         if !tc.has_focus {
             return false;
         }