Feat: background head-preload for sample libraries

crates/ratatui/src/editor.rs

@@ -1,3 +1,5 @@
+use std::cell::Cell;
+
 use crate::theme;
 use ratatui::{
     layout::Rect,
@@ -59,6 +61,7 @@ pub struct Editor {
     text: TextArea<'static>,
     completion: CompletionState,
     search: SearchState,
+    scroll_offset: Cell<u16>,
 }
 
 impl Editor {
@@ -107,6 +110,7 @@ impl Editor {
             text: TextArea::default(),
             completion: CompletionState::new(),
             search: SearchState::new(),
+            scroll_offset: Cell::new(0),
         }
     }
 
@@ -115,6 +119,7 @@ impl Editor {
         self.completion.active = false;
         self.search.query.clear();
         self.search.active = false;
+        self.scroll_offset.set(0);
     }
 
     pub fn set_candidates(&mut self, candidates: Vec<CompletionCandidate>) {
@@ -376,10 +381,21 @@ impl Editor {
             })
             .collect();
 
-        frame.render_widget(Paragraph::new(lines), area);
+        let viewport_height = area.height as usize;
+        let offset = self.scroll_offset.get() as usize;
+        let offset = if cursor_row < offset {
+            cursor_row
+        } else if cursor_row >= offset + viewport_height {
+            cursor_row - viewport_height + 1
+        } else {
+            offset
+        };
+        self.scroll_offset.set(offset as u16);
+
+        frame.render_widget(Paragraph::new(lines).scroll((offset as u16, 0)), area);
 
         if self.completion.active && !self.completion.matches.is_empty() {
-            self.render_completion(frame, area, cursor_row);
+            self.render_completion(frame, area, cursor_row - offset);
         }
     }