Expanding a tall <diff showLineNumbers> pinned to the scrollbox bottom froze
the TUI with ERR_INVALID_ARG_VALUE looping out of CliRenderer.loop every
frame. Root cause: @opentui/core 0.4.0 marshals OptimizedBuffer
fillRect/drawText/setCell* coordinates as u32 in the FFI table while
LineNumberRenderable.renderSelf passes raw screen coordinates — NEGATIVE when
the diff is partially scrolled above the viewport. Bun's FFI silently wraps
negatives (native side bounds-checks them into a no-op); Node's experimental
node:ffi rejects them. bufferDrawBox already uses i32, which is why ordinary
boxes/text scroll fine and only the diff line-background path crashed.
Fix at the seam we own: boundary/ffiSafe.ts patches OptimizedBuffer to clip
fillRect to the non-negative quadrant and skip negative-origin
drawText/setCell*/drawChar before the FFI call (Bun parity). Installed from
boundary/renderer.ts (live) and test/lib/render.ts (headless). TODO(upstream):
widen those FFI params to i32 so this shim can be deleted.
Ports the engine off the second JS runtime onto Node 26.3 (node:ffi) so the
repo ships a single JavaScript runtime: child_process for the gateway, vitest
for tests, an esbuild + Solid build step. Mouse selection copies the rendered
text you highlight, and the clipboard path is crash-proofed (a broken copy
pipe no longer quits the UI). Renames the engine dir ui-tui-opentui-v2/ ->
ui-opentui/ and updates the launcher/installer/Docker references.
