Constrained Streaming Layout

HotPDF can stage each completed page in file-backed storage, apply paragraph page-break constraints, expose bounded layout diagnostics, mark semantic paragraphs and pagination artefacts, and resolve paragraph base direction before emitting mixed-direction text

Immediate page flushing

Set ImmediateFlushLayout before BeginDoc for reports whose page count is not known in advance

When a page closes, its final compressed or uncompressed content stream moves from memory to an owned temporary-file stream whilst the PDF object remains available for normal cross-reference and resource finalisation

ImmediateFlushedPageCount and ImmediateFlushedBytes report the amount of staged content, and temporary files are deleted when their owning streams are released

Paragraph pagination

ParagraphIndex := PDF.CreateParagraph(0, jtLeft, 36, 36, 36, 36);
PDF.ConfigureParagraphPagination(ParagraphIndex, True, 2, 2);
PDF.ConfigureParagraphDirection(ParagraphIndex, pdAuto);
PDF.BeginParagraph(ParagraphIndex);
PDF.CurrentParagraph.ShowUnicodeText(BodyText);
PDF.EndParagraph;

KeepWithNext moves a paragraph when it would consume the final line that should remain for following content
MinOrphanLines prevents too few opening lines from being left at the bottom of a page
MinWidowLines advances a break when too few closing lines would remain on the next page
Automatic continuation preserves the source page width, height, font, margins, and paragraph settings
When ParaAutoAddPage is false, overflow stops on the current page and produces an ldkOverflow diagnostic

Layout diagnostics

THPDFLayoutDiagnostic records the THPDFLayoutDiagnosticKind, source and related page indexes, affected rectangle, line count, and an English reason for each retained decision

THPDFLayoutDiagnosticArray is returned by GetLayoutDiagnostics, whilst GetLayoutDiagnostic supports indexed access without allocating a copy

LayoutDiagnosticLimit bounds retained records and LayoutDiagnosticDroppedCount reports decisions discarded after that limit

ldkAutomaticPageBreak reports an ordinary continuation
ldkKeepWithNext, ldkOrphanControl, and ldkWidowControl identify the constraint that moved a break
ldkOverflow identifies content stopped by disabled automatic pagination
ldkImmediateFlush identifies a closed page moved to file-backed storage

Paragraph direction

THPDFParagraphDirection provides pdAuto, pdLeftToRight, and pdRightToLeft

DetectParagraphDirection applies first-strong-character resolution across BMP and supplementary-plane RTL scripts, so neutral prefixes and secondary directional runs do not choose the wrong base direction

Use ConfigureParagraphDirection for a persistent paragraph setting or the THPDFPara.Direction property for the active paragraph

PDF/UA paragraph semantics

Root := PDF.AddStructureElement('Document', nil);
Paragraph := PDF.BeginTaggedParagraph(Root, 'en-US', 'Accessible text');
PDF.CurrentPage.TextOut(36, 72, 0, WideString('Accessible text'));
PDF.EndTaggedParagraph;

PDF.BeginPaginationArtifact(pasHeader);
PDF.CurrentPage.TextOut(36, 20, 0, WideString('Running header'));
PDF.EndPaginationArtifact;

BeginTaggedParagraph emits a standard /P marked-content sequence with an allocated MCID, page parent-tree wiring, and optional /Lang and /ActualText values