diff --git a/src/lsp.rs b/src/lsp.rs
index db26709..963501a 100644
--- a/src/lsp.rs
+++ b/src/lsp.rs
@@ -141,7 +141,7 @@ impl Backend {
     async fn get_completions(&self, uri: Url, position: Position) -> Option<CompletionList> {
         // get new input
         let rope = self.documents.get(uri.as_str())?;
-        let encoding = self.encoding.read().await.clone();
+        let encoding = *self.encoding.read().await;
         let line_begin = {
             let line_pos = Position::new(position.line, 0);
             utils::position_to_offset(&rope, line_pos, encoding)?
@@ -184,7 +184,8 @@ impl Backend {
                 .and_then(utils::option_string)
                 .and_then(|rime_raw_input| new_input.borrow_pinyin().rfind(&rime_raw_input))
                 .unwrap_or(0);
-        let range = Range::new(utils::offset_to_position(&rope, real_offset)?, position);
+        let start_position = utils::offset_to_position(&rope, real_offset, encoding)?;
+        let range = Range::new(start_position, position);
         let filter_prefix = (self.config.read().await.long_filter_text).then_some(
             utils::surrounding_word(&Cow::from(rope.slice(line_begin..real_offset))),
         );
@@ -356,7 +357,7 @@ impl LanguageServer for Backend {
     }
 
     async fn did_change(&self, params: DidChangeTextDocumentParams) {
-        let encoding = self.encoding.read().await.clone();
+        let encoding = *self.encoding.read().await;
         let url = params.text_document.uri;
         if let Some(mut rope) = self.documents.get_mut(url.as_str()) {
             for change in params.content_changes {
diff --git a/src/utils.rs b/src/utils.rs
index b058170..d9c8c4a 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -4,9 +4,10 @@ use tower_lsp::lsp_types::{Position, PositionEncodingKind};
 
 use crate::consts::AUTO_TRIGGER_RE;
 
-#[derive(Clone, Copy)]
+#[derive(Default, Debug, Clone, Copy)]
 pub enum Encoding {
     UTF8,
+    #[default]
     UTF16,
     UTF32,
 }
@@ -21,22 +22,16 @@ impl Encoding {
     }
 }
 
-impl Default for Encoding {
-    fn default() -> Self {
-        Encoding::UTF16
-    }
-}
-
 pub fn select_encoding(options: Option<Vec<PositionEncodingKind>>) -> Encoding {
     match options {
-        // prefer utf-32 because of no conversion cost
+        // we prefer utf-32 here because there are no conversion costs
         Some(v) if v.contains(&PositionEncodingKind::new("utf-32")) => Encoding::UTF32,
         Some(v) if v.contains(&PositionEncodingKind::new("utf-8")) => Encoding::UTF8,
         _ => Encoding::default(),
     }
 }
 
-/// UTF-16 Position -> char index
+/// UTF-8/16/32 Position -> char index
 pub fn position_to_offset(rope: &Rope, position: Position, encoding: Encoding) -> Option<usize> {
     let (line, col) = (position.line as usize, position.character as usize);
     // position is at the end of rope
@@ -55,7 +50,7 @@ pub fn position_to_offset(rope: &Rope, position: Position, encoding: Encoding) -
     })
 }
 
-/// char index -> UTF-16 Position
+/// char index -> UTF-8/16/32 Position
 pub fn offset_to_position(rope: &Rope, offset: usize, encoding: Encoding) -> Option<Position> {
     let line = rope.try_char_to_line(offset).ok()?;
     let col_offset = offset - rope.try_line_to_char(line).ok()?;