fix(tui): Guard against degenerate scroll region when viewport fills screen#358
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…screen When the viewport occupies the entire terminal (area.top() == 0), insert_history_lines would emit \x1b[1;0r (DECSTBM with Pb=0), which terminals interpret as "full screen" rather than "empty region". This caused history content to scroll through and overwrite viewport rows, producing frozen/stale rows that ratatui's diff renderer could not detect. Add an early return when area.top() == 0 since there is no room above the viewport for history lines. 🤖 Generated with [Nori](https://usenori.ai) Co-Authored-By: Nori <contact@tilework.tech>
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Summary
🤖 Generated with Nori
insert_history_linesemitting a degenerate DECSTBM scroll region (\x1b[1;0r) when the viewport fills the entire terminal screen (area.top() == 0)Root Cause
SetScrollRegion(1..0)emits\x1b[1;0r. In DECSTBM,Pb=0means "bottom of screen", so the scroll region covers the entire terminal instead of being empty. Subsequent\r\n+ content writes scroll and overwrite viewport rows. Ratatui's diff-based renderer doesn't know the screen was corrupted, producing frozen/stale rows.Test Plan
full_screen_viewport_does_not_corrupt_display— confirms viewport content is unchanged wheninsert_history_linesis called with a full-screen viewporthistory_lines_inserted_above_viewport_with_room— confirms normal history insertion still works correctlytui-pty-e2e)Share Nori with your team: https://www.npmjs.com/package/nori-ai