Встраивайте workflow PDFium VCL Component в приложения Delphi и C++Builder или workflow PDFium LCL Component в Lazarus/FPC, используя компоненты с исходным кодом для просмотра, рендеринга, форм, печати, preflight-отчетов и проверки по стандартам.
Эта статья предназначена для developers building read-aloud, study, review, or assisted-reading features in Delphi PDF viewers. Она рассматривает word tracking and speech cursoring как промышленную инженерию документов, а не как одиночный вызов компонента.
Практический риск состоит в том, что speech highlighting becomes distracting or wrong when word boxes, ligatures, rotation, hidden text, and timing do not match the spoken stream. Поэтому процессу нужны письменный контракт, наблюдаемая диагностика и реалистичные регрессионные файлы.
Архитектурные решения
Synchronize speech with extracted text, not pixels alone. text extraction source, word segmentation policy, and language assumptions / highlight style, scroll behavior, pause and resume rules, and user controls
- text extraction source, word segmentation policy, and language assumptions
- highlight style, scroll behavior, pause and resume rules, and user controls
- fallback behavior for image-only pages, hidden text, ligatures, and rotated content
- whether speech timing is driven by the engine, the viewer, or a shared coordinator
Порядок реализации
Track words through a stable text map. The order below keeps the workflow reviewable for Delphi and C++Builder teams.
- extract page text and word bounds before speech playback begins
- build a word map that links text offsets, page numbers, and viewer coordinates
- call the tracking layer as the speech engine advances through words or offsets
- scroll the viewport only when the current word leaves the comfortable reading zone
- record skipped words, missing boxes, and timing drift for diagnostics
Доказательства проверки
Synchronization evidence for assisted reading. Keep these fields with the output or support record.
- page number, word text, text offset, bounding box, and speech timestamp
- tracking method used, including TrackReadingWordAt when the viewer supports it
- fallback reason for words without reliable geometry
- latency between speech event and visible cursor update
Word boxes are viewer data
Word-synchronized reading needs a mapping between extracted text, page coordinates, and speech timing. A robust implementation knows when text is unavailable, when a word box is ambiguous, and how to keep the viewport aligned with the current spoken word.
Review questions before release
Before this reaches production, the team should be able to answer these questions without reading source code.
- Who owns text extraction source, word segmentation policy, and language assumptions?
- What evidence proves page number, word text, text offset, bounding box, and speech timestamp?
- What happens when ligatures can represent multiple characters inside one visual glyph?
- Which regression file covers record skipped words, missing boxes, and timing drift for diagnostics?
Engineering review notes for word tracking and speech cursoring
Use these review notes to make sure the feature has moved beyond a demo and can be defended during release, support, and customer escalation.
- Decision: text extraction source, word segmentation policy, and language assumptions. Implementation pressure point: build a word map that links text offsets, page numbers, and viewer coordinates. Acceptance evidence: fallback reason for words without reliable geometry. Regression trigger: rapid speech rates can require coalescing highlight updates to avoid flicker
- Decision: highlight style, scroll behavior, pause and resume rules, and user controls. Implementation pressure point: call the tracking layer as the speech engine advances through words or offsets. Acceptance evidence: latency between speech event and visible cursor update. Regression trigger: ligatures can represent multiple characters inside one visual glyph
- Decision: fallback behavior for image-only pages, hidden text, ligatures, and rotated content. Implementation pressure point: scroll the viewport only when the current word leaves the comfortable reading zone. Acceptance evidence: page number, word text, text offset, bounding box, and speech timestamp. Regression trigger: rotated or vertical text needs coordinate handling separate from normal pages
Пограничные случаи
- ligatures can represent multiple characters inside one visual glyph
- rotated or vertical text needs coordinate handling separate from normal pages
- OCR text layers may not align perfectly with scanned images
- rapid speech rates can require coalescing highlight updates to avoid flicker
Delphi / C++Builder notes
PDFium Component should sit behind a small service boundary that receives files, streams, profiles, and credentials, then returns output paths, warnings, metrics, and validation status. Important terms include TrackReadingWordAt, speech cursor, word bounds, text extraction, highlight, reading assistance.
Пример кода Delphi
Следующий эскиз Delphi показывает практическую границу сервиса для этой темы. Оставляйте проверки политики, журналирование и валидацию вне узкого блока вызова продукта, чтобы сценарий было проще тестировать.
procedure TSpeechForm.SpeakWordAtCursor(PageNo, CharIndex: Integer);
var
UnitInfo: TReadingUnit;
begin
UnitInfo := LocateWordUnit(PdfView, PageNo, CharIndex);
HighlightBounds(UnitInfo.PageNo, UnitInfo.Bounds);
SpeechQueue.Speak(UnitInfo.Text);
StoreCursorPosition(UnitInfo.PageNo, UnitInfo.EndChar);
end;Производственный чек-лист
- Run the workflow on an empty file, a normal customer file, and a worst-case file
- Open the generated PDF with the target viewer, validator, printer, or downstream application
- Log product version, profile version, input hash, output path, elapsed time, and warning count
- Keep passwords, certificates, temporary files, and customer data under explicit retention rules
- Add regression documents when a customer file exposes a new edge case