fix(render): force per-frame clear in alt-screen to kill log-update drift#640
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…rift ink@7.0.2's log-update tracks previousLineCount as logical newlines, not visual rows. When any rendered line wraps because its visual width exceeds terminal columns — which happens on CJK / ambiguous-width content under East Asian terminals — the clear region on the next frame undershoots the actual on-screen footprint and the bottom of the previous frame survives. The reported symptom on Windows Terminal at 120×30 with zh-CN content is a duplicated status bar (two horizontal separators stacked) and stale residue creeping up from below. shouldClearTerminalForFrame already handles the overflow case, but it gates on Yoga's outputHeight — which can itself undercount visual rows for the same width-misjudgment reason, so the fallback misses exactly the cases that trigger the bug. Fix: in alt-screen mode, take the clearTerminal path unconditionally. Alt-screen has no scrollback, so per-frame clear costs nothing visible; incrementalRendering is already off (chat.tsx:571) so we're paying the full-frame stdout cost regardless. Patched via patch-package so the fix survives reinstalls until the same shape lands upstream. Closes #639
This was referenced May 11, 2026
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…rift (esengine#640) ink@7.0.2's log-update tracks previousLineCount as logical newlines, not visual rows. When any rendered line wraps because its visual width exceeds terminal columns — which happens on CJK / ambiguous-width content under East Asian terminals — the clear region on the next frame undershoots the actual on-screen footprint and the bottom of the previous frame survives. The reported symptom on Windows Terminal at 120×30 with zh-CN content is a duplicated status bar (two horizontal separators stacked) and stale residue creeping up from below. shouldClearTerminalForFrame already handles the overflow case, but it gates on Yoga's outputHeight — which can itself undercount visual rows for the same width-misjudgment reason, so the fallback misses exactly the cases that trigger the bug. Fix: in alt-screen mode, take the clearTerminal path unconditionally. Alt-screen has no scrollback, so per-frame clear costs nothing visible; incrementalRendering is already off (chat.tsx:571) so we're paying the full-frame stdout cost regardless. Patched via patch-package so the fix survives reinstalls until the same shape lands upstream. Closes esengine#639
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Summary
ink@7.0.2'srenderInteractiveFrameso that, in alt-screen mode, every frame is preceded byclearTerminalinstead oferaseLines(previousLineCount). Alt-screen has no scrollback, so the per-frame clear is invisible;incrementalRenderingis already disabled (src/cli/commands/chat.tsx:571) so we were already paying the full-frame stdout cost.patch-package+"postinstall": "patch-package"so the diff survives reinstalls.ink@7.0.2is the current latest on npm — no upstream release to bump to.Why the existing fallback didn't catch it
shouldClearTerminalForFrameinnode_modules/ink/build/ink.js:83-102already clears whenoutputHeight > viewportRows. ButoutputHeightcomes from Yoga, which measures viastring-width's default ambiguous-width = 1. On East Asian terminals that render those characters as width 2, Yoga undercounts and the fallback never fires — exactly the case that triggers the user-visible drift.The underlying log-update bookkeeping (
node_modules/ink/build/log-update.js:52) trackspreviousLineCount = lines.length(logical newlines), so when actual visual rows > logical rows,eraseLines(N)undershoots and the top of the previous frame survives. That's what the reporter's screenshot shows: a duplicated status bar with two horizontal separators stacked at the bottom of the viewport.Closes #639
Test plan
npm run verify— 2560 passed, 2 skippednpx patch-package ink;patches/ink+7.0.2.patchis the only diff againstnode_modules/ink/build/ink.jsUpstream
Worth filing the same change against
vadimdemedes/inkonce we have the reporter's confirmation — but we ship the local patch in the meantime so users don't wait on upstream review.