Fix space remaining (again) (#3377)

This commit was tested in a separate project

packages/cli/src/serve/output.rs

@@ -778,36 +778,32 @@ impl Output {
         // The viewport might be clipped, but the math still needs to work out.
         let actual_vh_height = self.viewport_current_height().min(term_size.height);
 
-        // We don't need to add any pushback if the frame is in the middle of the viewport
-        // We'll then add some pushback to ensure the log scrolls up above the viewport.
-        let max_scrollback = lines_printed.min(actual_vh_height.saturating_sub(1));
-
         // Move the terminal's cursor down to the number of lines printed
         let remaining_space = term_size
             .height
             .saturating_sub(frame_rect.y + frame_rect.height);
 
         // Calculate how many lines we need to push back
-        // - to_push equals lines_printed when the frame is at the bottom
-        // - to_push is zero when the remaining space is greater/equal than the scrollback (the frame will get pushed naturally)
-        let mut padding = max_scrollback.saturating_sub(remaining_space);
-
-        // The only reliable way we can force the terminal downards is through "insert_before"
+        // - padding equals lines_printed when the frame is at the bottom
+        // - padding is zero when the remaining space is greater/equal than the scrollback (the frame will get pushed naturally)
+        // Determine what extra padding is remaining after we've shifted the terminal down
+        // this will be the distance between the final line and the top of the frame, only if the
+        // final line has extended into the frame
+        let final_line = frame_rect.y + lines_printed;
+        let max_frame_top = term_size.height - actual_vh_height;
+        let padding = final_line
+            .saturating_sub(max_frame_top)
+            .clamp(0, actual_vh_height - 1);
+
+        // The only reliable way we can force the terminal downards is through "insert_before".
+        //
         // If we need to push the terminal down, we'll use this method with the number of lines
         // Ratatui will handle this rest.
-        // FIXME(jon): eventuallay insert_before will get scroll regions, breaking this, but making the logic here simpler
-        if padding == 0 {
-            terminal.insert_before(remaining_space.min(lines_printed), |_| {})?;
-
-            // Determine what extra padding is remaining after we've shifted the terminal down
-            // this will be the distance between the final line and the top of the frame, only if the
-            // final line has extended into the frame
-            let frame_top = term_size.height - actual_vh_height;
-            let end_y = (frame_rect.y + lines_printed).min(term_size.height);
-            if end_y > frame_top {
-                padding = end_y.saturating_sub(frame_top);
-            }
-        }
+        //
+        // This also calls `.clear()` so we don't need to call clear at the end of this function.
+        //
+        // FIXME(jon): eventually insert_before will get scroll regions, breaking this, but making the logic here simpler
+        terminal.insert_before(remaining_space.min(lines_printed), |_| {})?;
 
         // Wipe the viewport clean so it doesn't tear
         crossterm::queue!(
@@ -838,11 +834,6 @@ impl Output {
             )?;
         }
 
-        // Force a clear
-        // Might've been triggered by insert_before already, but supposedly double-queuing is fine
-        // since this isn't a "real" synchronous clear
-        terminal.clear()?;
-
         Ok(())
     }