refactor: move watermark and N-up off the UI thread#35
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Both tools loop over every page of the source PDF (watermark merges the overlay onto each, N-up calls show_pdf_page per source page), which freezes the UI on documents with more than a few dozen pages. Migrate both to BasePage._run_background, following the same pattern already used by compress / OCR / convert-images: - All input validation (file exists, watermark file non-empty, password unlock, cell-geometry sanity) stays on the main thread so errors surface as proper QMessageBoxes before any work starts. - The do_work closure is a tight loop with no Qt calls, only emits worker.progress.emit(pct, label) and checks worker.is_cancelled(). - on_done runs on the main thread (via the @slot dispatcher in worker.run_task) and shows the toast / pipeline_success. Add 4 new i18n keys × 8 languages for the progress messages (progress.watermark.applying / .page, progress.nup.placing / .page). Verified end-to-end on Ubuntu 26.04 + Py3.14.4: a smoke test that runs each tool through _run_background asserts on_done fires on the main thread and the output PDF is produced (5,749 bytes for the 8-page watermark sample, 5,266 bytes for the 4-up sheet). Page-numbers and import-pdf tools still run on the UI thread — deferred because page-numbers prompts the user mid-flow about existing numbers (needs main-thread split before/after the prompt) and import-pdf has 8 conversion paths that warrant individual review. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Migrate the watermark and N-up tools from synchronous UI-thread work to
BasePage._run_background, following the same pattern compress / OCR / convert-images already use. Both tools loop over every page of the source PDF, so on large documents the UI freezes during the entire run.Why now
Changes
do_workclosure that loops over pages emitting per-page progress.do_workclosure that builds output sheets callingshow_pdf_pagefor each cell, emitting per-source-page progress.progress.watermark.applying / .pageandprogress.nup.placing / .page.Deferred (separate PRs)
Test plan
_run_background, asserts_on_donefires on the main thread, asserts the output PDF is produced. Both pass.🤖 Generated with Claude Code