Highlight matching bracket when newest selection head is on a bracket

crates/editor/src/highlight_matching_bracket.rs

@@ -0,0 +1,40 @@
+use gpui::ViewContext;
+
+use crate::Editor;
+
+enum MatchingBracketHighlight {}
+
+pub fn refresh_matching_bracket_highlights(editor: &mut Editor, cx: &mut ViewContext<Editor>) {
+    editor.clear_background_highlights::<MatchingBracketHighlight>(cx);
+
+    let newest_selection = editor.selections.newest::<usize>(cx);
+    let snapshot = editor.snapshot(cx);
+    if let Some((opening_range, closing_range)) = snapshot
+        .buffer_snapshot
+        .enclosing_bracket_ranges(newest_selection.range())
+    {
+        let head = newest_selection.head();
+        let range_to_highlight = if opening_range.contains(&head) {
+            Some(closing_range)
+        } else if closing_range.contains(&head) {
+            Some(opening_range)
+        } else {
+            None
+        };
+
+        if let Some(range_to_highlight) = range_to_highlight {
+            let anchor_range = snapshot
+                .buffer_snapshot
+                .anchor_before(range_to_highlight.start)
+                ..snapshot
+                    .buffer_snapshot
+                    .anchor_after(range_to_highlight.end);
+
+            editor.highlight_background::<MatchingBracketHighlight>(
+                vec![anchor_range],
+                |theme| theme.editor.document_highlight_read_background,
+                cx,
+            )
+        }
+    }
+}