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DECSTBM constrains scrolling
When a scroll region is set via DECSTBM, scrolling (line feeds, index, SU/SD) should be constrained to the defined region. Lines outside the scroll region must remain fixed. This is the fundamental mechanism that enables fixed headers, footers, and split-screen layouts in TUI applications. Without proper scroll region isolation, tmux panes, vim status bars, and editor chrome would be disrupted by scrolling content.
How this is testedautomated
Write "FIXED_TOP" on row 0, set DECSTBM 3;10, move inside region, write enough lines to trigger scrolling, verify row 0 still contains "FIXED_TOP".
Write "FIXED_TOP" on row 0, set DECSTBM 3;10, move inside region, write enough lines to trigger scrolling, verify row 0 still contains "FIXED_TOP".
The same probe runs against headless backends (via Termless) and real terminal apps (via a daemon launched in each terminal). This lets us distinguish parser correctness from rendering correctness.
Analysis2026-04-06
Supported by all 12 tested terminals — universal adoption. Part of the Core TUI baseline.
Supported by 14 of 14 backends (100%)
Terminal Applications
| Terminal | Version | Support | Notes |
|---|---|---|---|
| iTerm2 | 3.6.9 | ✓ yes | |
| Ghostty | 1.3.1 | ✓ yes | |
| VS Code | ✓ yes | ||
| Warp | ✓ yes | ||
| Cursor | ✓ yes | ||
| Terminal.app | ✓ yes |