diff --git a/src/edit.rs b/src/edit.rs
index fa02a4249..8e96c0962 100644
--- a/src/edit.rs
+++ b/src/edit.rs
@@ -588,7 +588,7 @@ impl<'out, 'prompt, H: Helper> State<'out, 'prompt, H> {
         }
     }
 
-    /// Moves the cursor to the same column in the line above
+    /// Moves the cursor to the same column in the line below
     pub fn edit_move_line_down(&mut self, n: RepeatCount) -> Result<bool> {
         if self.line.move_to_line_down(n) {
             self.move_cursor()?;
diff --git a/src/layout.rs b/src/layout.rs
index 5aa8834fa..4ebdbd92e 100644
--- a/src/layout.rs
+++ b/src/layout.rs
@@ -1,5 +1,7 @@
 use std::cmp::Ordering;
 
+use crate::line_buffer::{ChangeListener, DeleteListener, Direction};
+
 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
 pub struct Position {
     pub col: usize, // The leftmost column is number 0.
@@ -21,13 +23,81 @@ impl Ord for Position {
     }
 }
 
+/// (byte offset in input buffer <=> Screen cell)
+pub type Cell = (usize, Position);
+
+/// All positions are relative to start of the prompt == origin (col: 0, row: 0)
 #[derive(Debug, Default)]
 pub struct Layout {
-    /// Prompt Unicode/visible width and height
+    /// Prompt Unicode/visible width and last row (relative)
     pub prompt_size: Position,
     pub default_prompt: bool,
     /// Cursor position (relative to the start of the prompt)
+    /// - cursor.row >= prompt_size.row
+    /// - if cursor.row >= prompt_size.row then cursor.col >=
+    ///   prompt_size.col/width
+    // FIXME
     pub cursor: Position,
-    /// Number of rows used so far (from start of prompt to end of input)
+    /// Number of rows used so far (from start of prompt to end
+    /// of input or hint)
+    /// - cursor <= end
+    // FIXME
     pub end: Position,
+    /// Input breaked into sorted cells
+    // TODO ignore zero-width grapheme (even '\n') ?
+    pub cells: Vec<Cell>,
+}
+
+impl Layout {
+    /// Find the nearest byte / grapheme offset in input buffer
+    /// matching `pos`
+    fn find_byte_by(&self, pos: Position) -> &Cell {
+        match self.cells.binary_search_by_key(&pos, |cell| cell.1) {
+            Ok(i) => &self.cells[i],
+            Err(i) => {
+                if i < self.cells.len() {
+                    &self.cells[i]
+                } else {
+                    todo!()
+                }
+            }
+        }
+    }
+
+    /// Find the nearest cell in screen matching `offset`
+    fn find_position_by(&self, offset: usize) -> &Cell {
+        match self.cells.binary_search_by_key(&offset, |cell| cell.0) {
+            Ok(i) => &self.cells[i],
+            Err(i) => {
+                if i < self.cells.len() {
+                    &self.cells[i]
+                } else {
+                    todo!()
+                }
+            }
+        }
+    }
+}
+
+// TODO Update (cursor, end, cells) accordingly
+// But we need to remember (old cursor/end row)
+impl DeleteListener for Layout {
+    fn delete(&mut self, idx: usize, string: &str, dir: Direction) {
+        todo!()
+    }
+}
+// TODO Update (cursor, end, cells) accordingly
+// But we need to remember (old cursor/end row)
+impl ChangeListener for Layout {
+    fn insert_char(&mut self, idx: usize, c: char) {
+        todo!()
+    }
+
+    fn insert_str(&mut self, idx: usize, string: &str) {
+        todo!()
+    }
+
+    fn replace(&mut self, idx: usize, old: &str, new: &str) {
+        todo!()
+    }
 }
diff --git a/src/line_buffer.rs b/src/line_buffer.rs
index ac9c68821..31ca6f6b2 100644
--- a/src/line_buffer.rs
+++ b/src/line_buffer.rs
@@ -582,6 +582,7 @@ impl LineBuffer {
     }
 
     /// Moves the cursor to the same column in the line above
+    // FIXME
     pub fn move_to_line_up(&mut self, n: RepeatCount) -> bool {
         match self.buf[..self.pos].rfind('\n') {
             Some(off) => {
@@ -610,6 +611,7 @@ impl LineBuffer {
     /// N lines up starting from the current one
     ///
     /// Fails if the cursor is on the first line
+    // FIXME
     fn n_lines_up(&self, n: RepeatCount) -> Option<(usize, usize)> {
         let mut start = if let Some(off) = self.buf[..self.pos].rfind('\n') {
             off + 1
@@ -633,6 +635,7 @@ impl LineBuffer {
     /// N lines down starting from the current one
     ///
     /// Fails if the cursor is on the last line
+    // FIXME
     fn n_lines_down(&self, n: RepeatCount) -> Option<(usize, usize)> {
         let mut end = if let Some(off) = self.buf[self.pos..].find('\n') {
             self.pos + off + 1
@@ -651,7 +654,8 @@ impl LineBuffer {
         Some((start, end))
     }
 
-    /// Moves the cursor to the same column in the line above
+    /// Moves the cursor to the same column in the line below
+    // FIXME
     pub fn move_to_line_down(&mut self, n: RepeatCount) -> bool {
         match self.buf[self.pos..].find('\n') {
             Some(off) => {
diff --git a/src/tty/mod.rs b/src/tty/mod.rs
index f2abf0df5..9317647d4 100644
--- a/src/tty/mod.rs
+++ b/src/tty/mod.rs
@@ -60,6 +60,7 @@ pub trait Renderer {
     /// Compute layout for rendering prompt + line + some info (either hint,
     /// validation msg, ...). on the screen. Depending on screen width, line
     /// wrapping may be applied.
+    // FIXME
     fn compute_layout(
         &self,
         prompt_size: Position,
@@ -67,6 +68,7 @@ pub trait Renderer {
         line: &LineBuffer,
         info: Option<&str>,
     ) -> Layout {
+        let mut cells = Vec::with_capacity(line.len());
         // calculate the desired position of the cursor
         let pos = line.pos();
         let cursor = self.calculate_position(&line[..pos], prompt_size);
@@ -85,6 +87,7 @@ pub trait Renderer {
             default_prompt,
             cursor,
             end,
+            cells,
         };
         debug_assert!(new_layout.prompt_size <= new_layout.cursor);
         debug_assert!(new_layout.cursor <= new_layout.end);
@@ -93,6 +96,7 @@ pub trait Renderer {
 
     /// Calculate the number of columns and rows used to display `s` on a
     /// `cols` width terminal starting at `orig`.
+    // FIXME
     fn calculate_position(&self, s: &str, orig: Position) -> Position;
 
     fn write_and_flush(&mut self, buf: &str) -> Result<()>;
diff --git a/src/tty/unix.rs b/src/tty/unix.rs
index edaea5470..daec80199 100644
--- a/src/tty/unix.rs
+++ b/src/tty/unix.rs
@@ -67,6 +67,7 @@ fn get_win_size(fd: RawFd) -> (usize, usize) {
                 } else {
                     size.ws_row as usize
                 };
+                debug!(target: "rustyline", "winsize: cols: {}, rows: {}", cols, rows);
                 (cols, rows)
             }
             _ => (80, 24),