fix: make scroll aware of tabs and wide characters (helix-editor#4519)

Author: mtoohey31

helix-term/src/commands.rs

@@ -1360,7 +1360,7 @@ pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
     let range = doc.selection(view.id).primary();
     let text = doc.text().slice(..);
 
-    let cursor = coords_at_pos(text, range.cursor(text));
+    let cursor = visual_coords_at_pos(text, range.cursor(text), doc.tab_width());
     let doc_last_line = doc.text().len_lines().saturating_sub(1);
 
     let last_line = view.last_line(doc);
@@ -1392,7 +1392,7 @@ pub fn scroll(cx: &mut Context, offset: usize, direction: Direction) {
 
     // If cursor needs moving, replace primary selection
     if line != cursor.row {
-        let head = pos_at_coords(text, Position::new(line, cursor.col), true); // this func will properly truncate to line end
+        let head = pos_at_visual_coords(text, Position::new(line, cursor.col), doc.tab_width()); // this func will properly truncate to line end
 
         let anchor = if cx.editor.mode == Mode::Select {
             range.anchor