fix: always clear new row cells during scroll to prevent stale data#134
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darrinm wants to merge 2 commits intocoder:mainfrom
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fix: always clear new row cells during scroll to prevent stale data#134darrinm wants to merge 2 commits intocoder:mainfrom
darrinm wants to merge 2 commits intocoder:mainfrom
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cursorDownScroll() only cleared new row cells when the cursor had a non-default background color. With default cursor style (after ESC[0m reset), new rows created during scrolling retained stale cell data from previously used page memory, causing periodic viewport corruption where content from old rows appeared horizontally merged into current rows. Make row clearing unconditional so stale cells never become visible, regardless of cursor style. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
cursorDownScroll()(Screen.zig patch)bg_color != .none)ESC[0mreset), new rows created during scrolling retained stale cell data from previously used page memoryThis caused periodic viewport corruption where content from old rows appeared horizontally merged into current rows. The bug was transient (self-correcting on the next write), periodic (~every 11 writes at cols=160), and affected all column widths at different frequencies.
Root cause
pages.grow()extends existing pages by appending rows, but the cell memory may contain data from previously erased rows.cursorDownScroll()was supposed to clear these cells, but the clearing was conditional onself.cursor.style.bg_color != .none. Programs that reset attributes withESC[0m(which setsbg_color = .none) left stale cells visible on empty lines.Test plan
bun test lib/viewport-row-merge.test.ts— 0 corrupt reps across all scrollback sizesbun test lib/viewport-corruption.test.ts— viewport corruption regression tests passbun test— full suite passes🤖 Generated with Claude Code