Trim lines to column num

src/main.rs

@@ -16,6 +16,8 @@
  * along with this program. If not, see https://www.gnu.org/licenses/.
  */
 
+use std::io::{stdout, Stdout, Write};
+
 use std::io::{ stdin, stdout, Read, Stdout, Write };
 
 use crossterm::{
@@ -41,16 +43,19 @@ impl Buffer {
     pub fn draw(&self, out: &mut (impl ExecutableCommand + Write)) -> Result<u32> {
         let (cols, rows) = terminal::size()?;
         let lr_width = self.text.len_lines().ilog10() + 1;
+        let gutter_width = lr_width + 1;
 
         out.execute(cursor::MoveTo(0, 0))?;
 
         for (row, line) in (0..rows).zip(self.text.lines()) {
             write!(out, "{:width$} ", row, width = lr_width as usize)?;
-            write!(out, "{}", line.as_str().unwrap_or("").trim_end())?;
+            let width = line.len_chars().saturating_sub(1); // lop off whitespace
+            let rhs = width.min(cols as usize - gutter_width as usize);
+            write!(out, "{}", line.slice(0..rhs))?;
             out.execute(cursor::MoveToNextLine(1))?;
         }
 
-        Ok(lr_width + 1)
+        Ok(gutter_width)
     }
 
     pub fn clamped_cursor(&self, cursor: Cursor) -> Cursor {