diff --git a/cove-tui/src/chat/tree/blocks.rs b/cove-tui/src/chat/tree/blocks.rs
index 6b5a221..a479947 100644
--- a/cove-tui/src/chat/tree/blocks.rs
+++ b/cove-tui/src/chat/tree/blocks.rs
@@ -6,6 +6,8 @@ use chrono::{DateTime, Utc};
 
 use crate::chat::Cursor;
 
+use super::util;
+
 pub struct Block<I> {
     pub id: I,
     pub line: i32,
@@ -118,9 +120,9 @@ impl<I: PartialEq> Blocks<I> {
         cursor.expect("no cursor in layout")
     }
 
-    pub fn calculate_offsets_with_cursor(&mut self, cursor: &Cursor<I>, height: i32) {
+    pub fn calculate_offsets_with_cursor(&mut self, cursor: &Cursor<I>, height: u16) {
         let cursor_index = self.mark_cursor(&cursor.id);
-        let cursor_line = ((height - 1) as f32 * cursor.proportion).floor() as i32;
+        let cursor_line = util::proportion_to_line(height, cursor.proportion);
 
         // Propagate lines from cursor to both ends
         self.blocks[cursor_index].line = cursor_line;
diff --git a/cove-tui/src/chat/tree/layout.rs b/cove-tui/src/chat/tree/layout.rs
index 55b4a84..7cc1cf7 100644
--- a/cove-tui/src/chat/tree/layout.rs
+++ b/cove-tui/src/chat/tree/layout.rs
@@ -99,7 +99,6 @@ impl<M: Msg> TreeView<M> {
         frame: &mut Frame,
         size: Size,
     ) -> Blocks<M::Id> {
-        let height: i32 = size.height.into();
         if let Some(cursor) = cursor {
             // TODO Ensure focus lies on cursor path, otherwise unfocus
             // TODO Unfold all messages on path to cursor
@@ -109,7 +108,7 @@ impl<M: Msg> TreeView<M> {
             let cursor_tree_id = cursor_path.first();
             let cursor_tree = store.tree(room, cursor_tree_id).await;
             let mut layout = layout_tree(frame, size, cursor_tree);
-            layout.calculate_offsets_with_cursor(cursor, height);
+            layout.calculate_offsets_with_cursor(cursor, size.height);
 
             // Expand upwards and downwards
             // TODO Don't do this if there is a focus
@@ -125,7 +124,7 @@ impl<M: Msg> TreeView<M> {
             // TODO Ensure there is no focus
 
             // Start at the bottom of the screen
-            let mut layout = Blocks::new_below(height - 1);
+            let mut layout = Blocks::new_below(size.height as i32 - 1);
 
             // Expand upwards until the edge of the screen
             if let Some(last_tree) = store.last_tree(room).await {
diff --git a/cove-tui/src/chat/tree/util.rs b/cove-tui/src/chat/tree/util.rs
index f1e7482..61fd56f 100644
--- a/cove-tui/src/chat/tree/util.rs
+++ b/cove-tui/src/chat/tree/util.rs
@@ -1,7 +1,7 @@
 //! Constants and helper functions.
 
 use crossterm::style::{ContentStyle, Stylize};
-use toss::frame::Frame;
+use toss::frame::{Frame, Size};
 
 pub const TIME_FORMAT: &str = "%H:%M ";
 pub const TIME_EMPTY: &str = "      ";
@@ -42,3 +42,15 @@ pub fn after_indent(indent: usize) -> i32 {
 pub fn after_nick(frame: &mut Frame, indent: usize, nick: &str) -> i32 {
     after_indent(indent) + 1 + frame.width(nick) as i32 + 2
 }
+
+pub fn proportion_to_line(height: u16, proportion: f32) -> i32 {
+    ((height - 1) as f32 * proportion).ceil() as i32
+}
+
+pub fn line_to_proportion(height: u16, line: i32) -> f32 {
+    if height > 1 {
+        line as f32 / (height - 1) as f32
+    } else {
+        0.0
+    }
+}