refactor(convert): move 6 PDF-export converters off the UI thread#36
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The PDF→DOCX / TXT / PPTX / XLSX / HTML / EPUB conversions still ran synchronously on the main thread, polling QApplication.processEvents() between pages. UI froze and the cancel button was effectively useless on multi-page documents (PPTX in particular renders each page at 2x DPI, several seconds per page). Migrate all 6 to BasePage._run_background, mirroring the pattern from the already-migrated _convert_images: - Pre-flight on the main thread: dependency check (ImportError → proper localized message via QMessageBox), open the doc once for page-count, capture self._pdf_password into a local before the closure. - do_work re-opens the fitz doc, re-authenticates if needed, runs the per-page extraction loop, emits worker.progress.emit(i, label) per page, and checks worker.is_cancelled() at each iteration so the Cancel button on the progress dialog actually aborts. - on_done runs on the main thread via the @slot dispatcher and shows the success toast / message box. Add 3 new i18n keys × 8 languages for the previously-missing dependency-error messages (tool.convert.dep_pptx / dep_xlsx / dep_epub) — before this PR those formats fell through to the generic str(e) error. Verified end-to-end on Ubuntu 26.04 + Py3.14.4 with a smoke test that runs all 6 converters on a 4-page sample and asserts on_done fires on the main thread + the output file is produced. Remaining background-task TODOs: import_pdf.py (8 paths) and page_numbers.py (mid-flow QMessageBox prompt). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Migrate the remaining 6 PDF-export converters (
_convert_docx/_convert_txt/_convert_pptx/_convert_xlsx/_convert_html/_convert_epub) from synchronous UI-thread loops withQApplication.processEvents()toBasePage._run_background, following the same pattern compress / OCR / convert-images / watermark / N-up already use.Why
PPTX and DOCX in particular render each page at high DPI (PPTX uses 2× pixmap matrix and embeds the image per slide); on multi-page documents the UI freezes for tens of seconds and the Cancel button is effectively dead because
processEventsonly runs between iterations. After this change the dialog is responsive andworker.is_cancelled()is honoured at every page boundary.Changes
ImportError→ localizedQMessageBox, open doc once forpage_count, captureself._pdf_password.do_workre-opens fitz, authenticates if needed, runs the per-page loop emittingworker.progress.emit(i, "i+1/total…")and checkingworker.is_cancelled().on_doneon main thread shows the success message.tool.convert.dep_pptx / dep_xlsx / dep_epub). Before this PR those three converters fell through to the genericstr(e)error on missing optional deps.Test plan
on_donefires on the main thread and the output file is produced. All 6 pass (txt 174B / docx 36KB / pptx 60KB / xlsx 6KB / html 563B / epub 3KB).Remaining work
After this lands, the only tools still doing heavy work synchronously are
import_pdf.py(8 conversion paths, each needs per-converter migration because they shell into different third-party libs) andpage_numbers.py(has a mid-flowQMessageBox.questionabout replacing existing numbers, needs main-thread split before/after the prompt). Tracked in [feedback_background_tasks.md](memory note).🤖 Generated with Claude Code