Font Fallback and Vertical Text

HotPDF can select fallback faces by Unicode script, report code points that remain unresolved, and write CJK text through a real vertical CID writing mode

Document-level fallback chains

THotPDF.SetFontFallbackChain stores an ordered face list for one THPDFFontScript category

THPDFPage.TextOutWithFallback resolves each Unicode scalar against the selected face, its script chain, and the common chain, then emits adjacent scalars with the same face as one text run

• Fallback chains are document settings and remain available across pages
• Duplicate and empty face names are removed whilst the caller's order is preserved
• Installed-face probing rejects silent GDI substitution before accepting coverage
• Supplementary-plane scalars are decoded from UTF-16 surrogate pairs before classification
• Each fallback run uses the existing embedded Type0 font, subsetting, ToUnicode, and shared cross-page font path
• Fallback layout checks installed font families with the requested bold and italic face, preserves all font style, charset, size, and writing-direction settings across runs, and restores the caller's font afterwards

Actionable diagnostics

AnalyzeUnresolvedGlyphs performs a read-only coverage audit, whilst TextOutWithFallback records unresolved scalars encountered during output

Each THPDFUnresolvedGlyphInfo includes the scalar code point, primary face, classified script, and a semicolon-separated fallback suggestion list

GetUnresolvedGlyphs returns the current document report and ClearUnresolvedGlyphs starts a new reporting interval

The explicit-style overloads of THotPDF.ResolveFontForCodePoint and THotPDF.AnalyzeUnresolvedGlyphs accept TFontStyles so preflight can inspect the same face used for output; their original overloads continue to inspect regular faces

Text boxes, SVG embedded text, and loaded text appearances retain styled font families through fallback layout, rather than treating PDF internal font names as system families or switching every run to a regular face

Vertical CJK writing

THPDFPage.TextOutVertical selects the current face's vertical variant and emits one Identity-V text run rather than positioning every character manually

• The CID descendant font contains /DW2 defaults and glyph-specific /W2 entries
• When present, OpenType vhea and vmtx supply vertical advances and VORG supplies vertical originsVORG supplies the authoritative CFF origin defaults and exceptions
• Fonts without vertical tables use configurable 1000-unit advance and 880-unit origin defaults
• With sfVerticalAlternates, the complete length-preserving GSUB run uses vrt2 when advertised and otherwise falls back to vert, preserving the active script and language selection
• When a font omits a punctuation substitution but maps Unicode vertical presentation forms, commas, stops, brackets, dashes, ellipses, and related punctuation use those glyphs while ToUnicode preserves the source text
• Existing vert, vrt2, and vertical GPOS features remain available through ShapingFeatures
• GetVerticalTextAdvance returns the user-space advance needed to position the next vertical run

Example

PDF.SetFontFallbackChain(hfsCJK,
  ['Microsoft YaHei UI', 'Yu Gothic UI', 'Malgun Gothic']);
PDF.SetFontFallbackChain(hfsEmoji, ['Segoe UI Emoji']);

PDF.CurrentPage.SetFont('Arial', [], 12);
PDF.CurrentPage.TextOutWithFallback(72, 72, 0, Text);

PDF.CurrentPage.SetFont('Yu Gothic UI', [], 14);
PDF.CurrentPage.TextOutVertical(420, 72, VerticalText);

Missing := PDF.GetUnresolvedGlyphs;

Related APIs

• THotPDF font fallback and glyph diagnostic methods
• THPDFPage fallback and vertical text methods
• THPDFPage.SetFont