FIX: Undo/redo delete/add page

Now we can undo adding or deleting worksheets

base/src/test/user_model/test_sheets_undo_redo.rs

@@ -0,0 +1,52 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::test::util::new_empty_model;
+use crate::UserModel;
+
+#[test]
+fn basic_undo_redo() {
+    let model = new_empty_model();
+    let mut model = UserModel::from_model(model);
+    assert_eq!(model.get_selected_sheet(), 0);
+
+    model.new_sheet().unwrap();
+    assert_eq!(model.get_selected_sheet(), 1);
+    model.undo().unwrap();
+    assert_eq!(model.get_selected_sheet(), 0);
+    {
+        let props = model.get_worksheets_properties();
+        assert_eq!(props.len(), 1);
+        let view = model.get_selected_view();
+        assert_eq!(view.sheet, 0);
+    }
+
+    model.redo().unwrap();
+    assert_eq!(model.get_selected_sheet(), 1);
+    {
+        let props = model.get_worksheets_properties();
+        assert_eq!(props.len(), 2);
+        let view = model.get_selected_view();
+
+        assert_eq!(view.sheet, 1);
+    }
+}
+
+#[test]
+fn delete_undo() {
+    let model = new_empty_model();
+    let mut model = UserModel::from_model(model);
+    assert_eq!(model.get_selected_sheet(), 0);
+
+    model.new_sheet().unwrap();
+    assert_eq!(model.get_selected_sheet(), 1);
+    model.set_user_input(1, 1, 1, "42").unwrap();
+    model.set_user_input(1, 1, 2, "=A1*2").unwrap();
+    model.delete_sheet(1).unwrap();
+
+    assert_eq!(model.get_selected_sheet(), 0);
+
+    model.undo().unwrap();
+    assert_eq!(model.get_selected_sheet(), 1);
+    model.redo().unwrap();
+    assert_eq!(model.get_selected_sheet(), 0);
+}