Fixed a couple of bugs that crashed at tiny terminal sizes.

src/buffer/mod.rs

@@ -320,7 +320,7 @@ impl Buffer {
             let l_start = self.text.line_to_char(pos.0);
             let l_end = self.text.line_to_char(pos.0 + 1);
             return (l_start + pos.1)
-                .min(l_start.max(l_end - 1))
+                .min(l_start.max(l_end - 1.min(l_end)))
                 .min(self.text.len_chars());
         } else {
             return self.text.len_chars();

src/formatter.rs

@@ -7,7 +7,7 @@ use buffer::Buffer;
 // This is necessary to prevent pathological formatting cases which
 // could slow down the editor arbitrarily for arbitrarily long
 // lines.
-pub const LINE_BLOCK_LENGTH: usize = 4096;
+pub const LINE_BLOCK_LENGTH: usize = 1 << 12;
 
 #[derive(Copy, Clone, PartialEq)]
 pub enum RoundingBehavior {

src/term_ui/screen.rs

@@ -89,20 +89,26 @@ impl Screen {
     }
 
     pub(crate) fn draw(&self, x: usize, y: usize, text: &str, style: Style) {
+        if y < self.h {
             let mut buf = self.buf.borrow_mut();
             let mut x = x;
             for g in UnicodeSegmentation::graphemes(text, true) {
                 let width = UnicodeWidthStr::width(g);
                 if width > 0 {
+                    if x < self.w {
                         buf[y * self.w + x] = Some((style, g.into()));
+                    }
                     x += 1;
                     for _ in 0..(width - 1) {
+                        if x < self.w {
                             buf[y * self.w + x] = None;
+                        }
                         x += 1;
                     }
                 }
             }
         }
+    }
 
     pub(crate) fn hide_cursor(&self) {
         write!(self.out.borrow_mut(), "{}", termion::cursor::Hide).unwrap();