2 files changed, 53 insertions(+), 11 deletions(-)

M src/app.rs
M src/main.rs

@@ 97,10 97,43 @@ impl InputBuffer {
         // adjust viewspan to match current terminal width (less the prompt)
         if self.span_len() > width_with_prompt {
             // shrink the view span
-            self.end -= self.span_len() - width_with_prompt;
+            let delta = self.span_len() - width_with_prompt;
+
+            let trailing_width = self.buffer.len() - self.pos;
+            
+            if self.pos + trailing_width > width_with_prompt {
+                let start_to_pos = self.pos - self.start;
+                self.start = self.pos;
+
+                if start_to_pos < delta {
+                    self.end -= delta - start_to_pos;
+                }
+            } else {
+                self.end -= delta;
+            }
         } else if self.span_len() < width_with_prompt {
             // grow the view span
-            self.end += width_with_prompt - self.span_len();
+            let mut delta = width_with_prompt - self.span_len();
+
+            // consume delta to display tail of the buffer outside the viewport.
+            if self.buffer.len() > self.end {
+                let overhang = cmp::min(delta, self.buffer.len() - self.end);
+                self.end += overhang;
+                delta -= overhang;
+            }
+
+            // repeat the same for the head of the buffer outside the viewport.
+            if self.start > 0 {
+                let overhang = cmp::min(delta, self.start);
+                self.start -= overhang;
+                delta -= overhang;
+            }
+
+            // if we still have new columns place them on the end.
+            //
+            // this should only be the case if the input span is larger than
+            // the current buffer.
+            self.end += delta;
         }
 
         // draw status info on line 2


@@ 123,10 156,12 @@ impl InputBuffer {
             .queue(Clear(ClearType::CurrentLine))?
             .queue(Print(prompt.to_string()))?;
 
-        // draw the current viewport
+        // render the current viewport & update the cursor
+        let beg = self.start;
+        let end = cmp::min(self.buffer.len(), self.end);
         let relative_cursor_pos = (self.pos - self.start) + prompt.len() + 1;
         stdout
-            .queue(Print(&self.buffer[self.start..]))?
+            .queue(Print(&self.buffer[beg..end]))?
             .queue(cursor::MoveToColumn(relative_cursor_pos as u16))?;
 
         Ok(stdout.flush()?)

@@ 16,8 16,19 @@ mod app;
 
 
 fn main() -> anyhow::Result<()> {
-
 	crossterm::terminal::enable_raw_mode()?;
+
+	let res = std::panic::catch_unwind(|| {
+		ui_thread()
+	});
+
+	crossterm::terminal::disable_raw_mode()?;
+	println!("panic: {:?}", res);
+	
+	Ok(())
+}
+
+fn ui_thread() -> anyhow::Result<()> {
 	
 	let mut shell = app::Shell::new()?;
 	let poll_hz = Duration::from_millis(1000 / 120);


@@ 47,10 58,6 @@ fn main() -> anyhow::Result<()> {
 		.execute(LeaveAlternateScreen)?
 		.execute(cursor::Show)?;
 	crossterm::terminal::disable_raw_mode()?;
-	Ok(())
-}
-
-
-
-
 
+	Ok(())
+}<
\ No newline at end of file