editor: Use proper rows for fold indicators in the gutter (#11741)

Follow-up to #11656

Release Notes:

- N/A

---------

Co-authored-by: Kirill <kirill@zed.dev>

crates/editor/src/display_map.rs

@@ -70,17 +70,6 @@ pub trait ToDisplayPoint {
 type TextHighlights = TreeMap<Option<TypeId>, Arc<(HighlightStyle, Vec<Range<Anchor>>)>>;
 type InlayHighlights = TreeMap<TypeId, TreeMap<InlayId, (HighlightStyle, InlayHighlight)>>;
 
-#[derive(Clone)]
-pub struct DisplayBufferRows<'a>(BlockBufferRows<'a>);
-
-impl<'a> Iterator for DisplayBufferRows<'a> {
-    type Item = Option<DisplayRow>;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.0.next().map(|row| row.map(|r| DisplayRow(r.0)))
-    }
-}
-
 /// Decides how text in a [`MultiBuffer`] should be displayed in a buffer, handling inlay hints,
 /// folding, hard tabs, soft wrapping, custom blocks (like diagnostics), and highlighting.
 ///
@@ -398,8 +387,13 @@ impl DisplaySnapshot {
         self.buffer_snapshot.len() == 0
     }
 
-    pub fn display_rows(&self, start_row: DisplayRow) -> DisplayBufferRows {
-        DisplayBufferRows(self.block_snapshot.buffer_rows(BlockRow(start_row.0)))
+    pub fn buffer_rows(
+        &self,
+        start_row: DisplayRow,
+    ) -> impl Iterator<Item = Option<MultiBufferRow>> + '_ {
+        self.block_snapshot
+            .buffer_rows(BlockRow(start_row.0))
+            .map(|row| row.map(|row| MultiBufferRow(row.0)))
     }
 
     pub fn max_buffer_row(&self) -> MultiBufferRow {

crates/editor/src/element.rs

@@ -1516,7 +1516,7 @@ impl EditorElement {
         let end = rows.end.max(relative_to);
 
         let buffer_rows = snapshot
-            .display_rows(start)
+            .buffer_rows(start)
             .take(1 + end.minus(start) as usize)
             .collect::<Vec<_>>();
 
@@ -1554,7 +1554,7 @@ impl EditorElement {
     fn layout_line_numbers(
         &self,
         rows: Range<DisplayRow>,
-        buffer_rows: impl Iterator<Item = Option<DisplayRow>>,
+        buffer_rows: impl Iterator<Item = Option<MultiBufferRow>>,
         active_rows: &BTreeMap<DisplayRow, bool>,
         newest_selection_head: Option<DisplayPoint>,
         snapshot: &EditorSnapshot,
@@ -1602,10 +1602,10 @@ impl EditorElement {
             } else {
                 (false, cx.theme().colors().editor_line_number)
             };
-            if let Some(display_row) = row {
+            if let Some(multibuffer_row) = row {
                 if include_line_numbers {
                     line_number.clear();
-                    let default_number = display_row.0 + 1;
+                    let default_number = multibuffer_row.0 + 1;
                     let number = relative_rows
                         .get(&DisplayRow(ix as u32 + rows.start.0))
                         .unwrap_or(&default_number);
@@ -1628,9 +1628,6 @@ impl EditorElement {
                     fold_statuses.push(
                         is_singleton
                             .then(|| {
-                                let multibuffer_point =
-                                    DisplayPoint::new(display_row, 0).to_point(snapshot);
-                                let multibuffer_row = MultiBufferRow(multibuffer_point.row);
                                 snapshot
                                     .fold_for_line(multibuffer_row)
                                     .map(|fold_status| (fold_status, multibuffer_row, active))
@@ -3861,8 +3858,9 @@ impl Element for EditorElement {
                 let end_row = DisplayRow(end_row);
 
                 let buffer_rows = snapshot
-                    .display_rows(start_row)
-                    .take((start_row..end_row).len());
+                    .buffer_rows(start_row)
+                    .take((start_row..end_row).len())
+                    .collect::<Vec<_>>();
 
                 let start_anchor = if start_row == Default::default() {
                     Anchor::min()
@@ -3905,7 +3903,7 @@ impl Element for EditorElement {
 
                 let (line_numbers, fold_statuses) = self.layout_line_numbers(
                     start_row..end_row,
-                    buffer_rows.clone(),
+                    buffer_rows.clone().into_iter(),
                     &active_rows,
                     newest_selection_head,
                     &snapshot,
@@ -3975,11 +3973,7 @@ impl Element for EditorElement {
                 }
 
                 let blamed_display_rows = self.layout_blame_entries(
-                    buffer_rows.map(|display_row| {
-                        display_row.map(|row| {
-                            MultiBufferRow(DisplayPoint::new(row, 0).to_point(&snapshot).row)
-                        })
-                    }),
+                    buffer_rows.into_iter(),
                     em_width,
                     scroll_position,
                     line_height,
@@ -4884,7 +4878,7 @@ mod tests {
                 element
                     .layout_line_numbers(
                         DisplayRow(0)..DisplayRow(6),
-                        (0..6).map(DisplayRow).map(Some),
+                        (0..6).map(MultiBufferRow).map(Some),
                         &Default::default(),
                         Some(DisplayPoint::new(DisplayRow(0), 0)),
                         &snapshot,