revert additional change on grid

rio-backend/src/crosswords/grid/mod.rs

@@ -207,42 +207,34 @@ impl<T: GridSquare + Default + PartialEq + Clone> Grid<T> {
                 min(self.display_offset + positions, self.max_scroll_limit);
         }
 
-        // Only rotate the entire history if the active region starts at the top.
-        if region.start == 0 {
-            // Create scrollback for the new lines.
-            self.increase_scroll_limit(positions);
+        // Create scrollback for the new lines.
+        self.increase_scroll_limit(positions);
 
-            // Swap the lines fixed at the top to their target positions after rotation.
-            //
-            // Since we've made sure that the rotation will never rotate away the entire region, we
-            // know that the position of the fixed lines before the rotation must already be
-            // visible.
-            //
-            // We need to start from the bottom, to make sure the fixed lines aren't swapped with
-            // each other.
-            for i in (0..region.start.0).rev().map(Line::from) {
-                self.raw.swap(i, i + positions);
-            }
-
-            // Rotate the entire line buffer upward.
-            self.raw.rotate(-(positions as isize));
-
-            // Swap the fixed lines at the bottom back into position.
-            let screen_lines = self.screen_lines() as i32;
-            for i in (region.end.0..screen_lines).rev().map(Line::from) {
-                self.raw.swap(i, i - positions);
-            }
-        } else {
-            // Rotate lines without moving anything into history.
-            for i in (region.start.0..region.end.0 - positions as i32).map(Line::from) {
-                self.raw.swap(i, i + positions);
-            }
+        // Swap the lines fixed at the top to their target positions after rotation.
+        //
+        // Since we've made sure that the rotation will never rotate away the entire region, we
+        // know that the position of the fixed lines before the rotation must already be
+        // visible.
+        //
+        // We need to start from the bottom, to make sure the fixed lines aren't swapped with each
+        // other.
+        for i in (0..region.start.0).rev().map(Line::from) {
+            self.raw.swap(i, i + positions);
         }
 
+        // Rotate the entire line buffer upward.
+        self.raw.rotate(-(positions as isize));
+
         // Ensure all new lines are fully cleared.
-        for i in (region.end.0 - positions as i32..region.end.0).map(Line::from) {
+        let screen_lines = self.screen_lines();
+        for i in ((screen_lines - positions)..screen_lines).map(Line::from) {
             self.raw[i].reset(&self.cursor.template);
         }
+
+        // Swap the fixed lines at the bottom back into position.
+        for i in (region.end.0..(screen_lines as i32)).rev().map(Line::from) {
+            self.raw.swap(i, i - positions);
+        }
     }
 
     pub fn clear_viewport<D>(&mut self)