Compute scrollbar markers asynchronously (#10080)

Refs #9647
Fixes https://github.com/zed-industries/zed/issues/9792

This pull request moves the computation of scrollbar markers off the
main thread, to prevent them from grinding the editor to a halt when we
have a lot of them (e.g., when there are lots of search results on a
large file). With these changes we also avoid generating multiple quads
for adjacent markers, thus fixing an issue where we stop drawing other
primitives because we've drawn too many quads in the scrollbar.

Release Notes:

- Improved editor performance when displaying lots of search results,
diagnostics, or symbol highlights in the scrollbar
([#9792](https://github.com/zed-industries/zed/issues/9792)).

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Nathan <nathan@zed.dev>

crates/editor/src/display_map.rs

@@ -26,7 +26,7 @@ mod wrap_map;
 use crate::EditorStyle;
 use crate::{hover_links::InlayHighlight, movement::TextLayoutDetails, InlayId};
 pub use block_map::{BlockMap, BlockPoint};
-use collections::{BTreeMap, HashMap, HashSet};
+use collections::{HashMap, HashSet};
 use fold_map::FoldMap;
 use gpui::{Font, HighlightStyle, Hsla, LineLayout, Model, ModelContext, Pixels, UnderlineStyle};
 use inlay_map::InlayMap;
@@ -63,7 +63,7 @@ pub trait ToDisplayPoint {
 }
 
 type TextHighlights = TreeMap<Option<TypeId>, Arc<(HighlightStyle, Vec<Range<Anchor>>)>>;
-type InlayHighlights = BTreeMap<TypeId, HashMap<InlayId, (HighlightStyle, InlayHighlight)>>;
+type InlayHighlights = TreeMap<TypeId, TreeMap<InlayId, (HighlightStyle, InlayHighlight)>>;
 
 /// 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.
@@ -257,10 +257,15 @@ impl DisplayMap {
         style: HighlightStyle,
     ) {
         for highlight in highlights {
-            self.inlay_highlights
-                .entry(type_id)
-                .or_default()
-                .insert(highlight.inlay, (style, highlight));
+            let update = self.inlay_highlights.update(&type_id, |highlights| {
+                highlights.insert(highlight.inlay, (style, highlight.clone()))
+            });
+            if update.is_none() {
+                self.inlay_highlights.insert(
+                    type_id,
+                    TreeMap::from_ordered_entries([(highlight.inlay, (style, highlight))]),
+                );
+            }
         }
     }
 
@@ -354,6 +359,7 @@ pub struct HighlightedChunk<'a> {
     pub is_tab: bool,
 }
 
+#[derive(Clone)]
 pub struct DisplaySnapshot {
     pub buffer_snapshot: MultiBufferSnapshot,
     pub fold_snapshot: fold_map::FoldSnapshot,
@@ -872,7 +878,7 @@ impl DisplaySnapshot {
     #[cfg(any(test, feature = "test-support"))]
     pub(crate) fn inlay_highlights<Tag: ?Sized + 'static>(
         &self,
-    ) -> Option<&HashMap<InlayId, (HighlightStyle, InlayHighlight)>> {
+    ) -> Option<&TreeMap<InlayId, (HighlightStyle, InlayHighlight)>> {
         let type_id = TypeId::of::<Tag>();
         self.inlay_highlights.get(&type_id)
     }
@@ -1093,7 +1099,7 @@ pub mod tests {
                                         position,
                                         height,
                                         disposition,
-                                        render: Arc::new(|_| div().into_any()),
+                                        render: Box::new(|_| div().into_any()),
                                     }
                                 })
                                 .collect::<Vec<_>>();