Fix perf problem with scrollbars in large multibuffers (#2505)

Remove scrollbars from multibuffers

Release Notes:

* Removes git scrollbar highlights from multibuffers (preview only)

crates/editor/src/editor.rs

@@ -518,11 +518,8 @@ pub struct EditorSnapshot {
 }
 
 impl EditorSnapshot {
-    fn has_scrollbar_info(&self) -> bool {
-        self.buffer_snapshot
-            .git_diff_hunks_in_range(0..self.max_point().row())
-            .next()
-            .is_some()
+    fn has_scrollbar_info(&self, is_singleton: bool) -> bool {
+        is_singleton && self.buffer_snapshot.has_git_diffs()
     }
 }
 

crates/editor/src/element.rs

@@ -1047,7 +1047,8 @@ impl EditorElement {
                 ..Default::default()
             });
 
-            let diff_style = cx.global::<Settings>().theme.editor.diff.clone();
+            if layout.is_singleton {
+                let diff_style = theme::current(cx).editor.diff.clone();
                 for hunk in layout
                     .position_map
                     .snapshot
@@ -1093,6 +1094,7 @@ impl EditorElement {
                         corner_radius: style.thumb.corner_radius,
                     })
                 }
+            }
 
             scene.push_quad(Quad {
                 bounds: thumb_bounds,
@@ -2063,9 +2065,10 @@ impl Element<Editor> for EditorElement {
             ));
         }
 
-        let show_scrollbars = match cx.global::<Settings>().show_scrollbars {
-            settings::ShowScrollbars::Auto => {
-                snapshot.has_scrollbar_info() || editor.scroll_manager.scrollbars_visible()
+        let show_scrollbars = match settings::get::<EditorSettings>(cx).show_scrollbars {
+            ShowScrollbars::Auto => {
+                snapshot.has_scrollbar_info(is_singleton)
+                    || editor.scroll_manager.scrollbars_visible()
             }
             settings::ShowScrollbars::System => editor.scroll_manager.scrollbars_visible(),
             settings::ShowScrollbars::Always => true,
@@ -2288,6 +2291,7 @@ impl Element<Editor> for EditorElement {
                 text_size,
                 scrollbar_row_range,
                 show_scrollbars,
+                is_singleton,
                 max_row,
                 gutter_margin,
                 active_rows,
@@ -2443,6 +2447,7 @@ pub struct LayoutState {
     selections: Vec<(ReplicaId, Vec<SelectionLayout>)>,
     scrollbar_row_range: Range<f32>,
     show_scrollbars: bool,
+    is_singleton: bool,
     max_row: u32,
     context_menu: Option<(DisplayPoint, AnyElement<Editor>)>,
     code_actions_indicator: Option<(u32, AnyElement<Editor>)>,

crates/editor/src/multi_buffer.rs

@@ -2820,6 +2820,15 @@ impl MultiBufferSnapshot {
             })
     }
 
+    pub fn has_git_diffs(&self) -> bool {
+        for excerpt in self.excerpts.iter() {
+            if !excerpt.buffer.git_diff.is_empty() {
+                return true;
+            }
+        }
+        false
+    }
+
     pub fn git_diff_hunks_in_range_rev<'a>(
         &'a self,
         row_range: Range<u32>,

crates/git/src/diff.rs

@@ -71,6 +71,10 @@ impl BufferDiff {
         }
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.tree.is_empty()
+    }
+
     pub fn hunks_in_row_range<'a>(
         &'a self,
         range: Range<u32>,