Use same saved cursor logic in height resize as width

See zellij-org#2182 for original introduction that only added it in one branch,
this fixes an issue where the saved cursor was incorrectly reset when
the real cursor was

zellij-server/src/panes/grid.rs

@@ -923,7 +923,7 @@ impl Grid {
                 self.saved_cursor_position.as_ref().map(|saved_cursor| saved_cursor.y);
 
             let new_cursor_x = self.cursor.x;
-            let mut saved_cursor_x_coordinates =
+            let saved_cursor_x_coordinates =
                 self.saved_cursor_position.as_ref().map(|saved_cursor| saved_cursor.x);
 
             let current_viewport_row_count = self.viewport.len();
@@ -947,15 +947,15 @@ impl Grid {
                     let row_count_to_transfer = current_viewport_row_count - new_rows;
                     if row_count_to_transfer > new_cursor_y {
                         new_cursor_y = 0;
-                        if let Some(saved_cursor_y_coordinates) = saved_cursor_y_coordinates.as_mut() {
-                            *saved_cursor_y_coordinates = 0
-                        };
                     } else {
                         new_cursor_y -= row_count_to_transfer;
-                        if let Some(saved_cursor_y_coordinates) = saved_cursor_y_coordinates.as_mut() {
-                            *saved_cursor_y_coordinates = saved_cursor_y_coordinates
-                                .saturating_sub(row_count_to_transfer);
-                        };
+                    }
+                    if let Some(saved_cursor_y_coordinates) = saved_cursor_y_coordinates.as_mut() {
+                        if row_count_to_transfer > *saved_cursor_y_coordinates {
+                            *saved_cursor_y_coordinates = 0;
+                        } else {
+                            *saved_cursor_y_coordinates -= row_count_to_transfer;
+                        }
                     }
                     transfer_rows_from_viewport_to_lines_above(
                         &mut self.viewport,

zellij-server/src/panes/unit/grid_tests.rs

@@ -2400,6 +2400,48 @@ pub fn scroll_up_increase_width_and_scroll_down() {
     assert_snapshot!(format!("{:?}", grid));
 }
 
+#[test]
+fn saved_cursor_across_resize() {
+    let mut vte_parser = vte::Parser::new();
+    let sixel_image_store = Rc::new(RefCell::new(SixelImageStore::default()));
+    let terminal_emulator_color_codes = Rc::new(RefCell::new(HashMap::new()));
+    let debug = false;
+    let arrow_fonts = true;
+    let styled_underlines = true;
+    let mut grid = Grid::new(
+        4,
+        20,
+        Rc::new(RefCell::new(Palette::default())),
+        terminal_emulator_color_codes,
+        Rc::new(RefCell::new(LinkHandler::new())),
+        Rc::new(RefCell::new(None)),
+        sixel_image_store,
+        Style::default(),
+        debug,
+        arrow_fonts,
+        styled_underlines,
+    );
+    let mut parse = |s, grid: &mut Grid|
+        for b in Vec::from(s) { vte_parser.advance(&mut *grid, b) };
+    let content = "\n
+\rLine 1 >fill to 20_<
+\rLine 2 >fill to 20_<
+\rLine 3 >fill to 20_<
+\rL\u{1b}[sine 4 >fill to 20_<";
+    parse(content, &mut grid);
+    // Move real cursor position up three lines
+    let content = "\u{1b}[3A";
+    parse(content, &mut grid);
+    // Truncate top of terminal, resetting cursor (but not saved cursor)
+    grid.change_size(3, 20);
+    // Wrap, resetting cursor again (but not saved cursor)
+    grid.change_size(3, 10);
+    // Restore saved cursor position and write ZZZ
+    let content = "\u{1b}[uZZZ";
+    parse(content, &mut grid);
+    assert_snapshot!(format!("{:?}", grid));
+}
+
 #[test]
 pub fn move_cursor_below_scroll_region() {
     let mut vte_parser = vte::Parser::new();

zellij-server/src/panes/unit/snapshots/zellij_server__panes__grid__grid_tests__saved_cursor_across_resize.snap

@@ -0,0 +1,9 @@
+---
+source: zellij-server/src/panes/./unit/grid_tests.rs
+assertion_line: 2443
+expression: "format!(\"{:?}\", grid)"
+---
+00 (W): ll to 20_<
+01 (C): LZZZ 4 >fi
+02 (W): ll to 20_<
+