feat(forms): support CID fonts in form field appearances

[Mythie]

CID-keyed fonts (Type0 with Identity-H/V encoding) can now be used
for form field appearance generation. This enables correct rendering
of CJK and Unicode text in existing PDF form fonts.

Key changes:

• CIDFont: add Unicode→charcode mapping, glyph renderability checks,
  and ToUnicode reverse lookup for accurate encoding
• FontProgram: add hasRenderableGlyph() and getGlyphIdForUnicode()
  across all font program types (TrueType, CFF, CFF-CID, Type1)
• ExistingFont: full CID font encoding support with canUseForAppearance
  validation and 2-byte character code generation
• Deduplicate ~500 lines of shared helpers from button/text/choice
  appearance generators into appearance-utils.ts
• Consolidate duplicate Standard 14 alias tables into single source

[vercel]

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Project	Deployment	Actions	Updated (UTC)
core	Ready	Preview, Comment	Mar 11, 2026 2:22am

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Benchmark Results

Comparison

Load PDF

Benchmark	Mean	p99	RME	Samples
libpdf	2.40ms	3.15ms	±1.2%	209
pdf-lib	38.75ms	43.52ms	±4.5%	13

Create blank PDF

Benchmark	Mean	p99	RME	Samples
libpdf	44μs	87μs	±1.7%	11363
pdf-lib	348μs	1.43ms	±2.7%	1439

Add 10 pages

Benchmark	Mean	p99	RME	Samples
libpdf	81μs	152μs	±1.1%	6155
pdf-lib	436μs	1.73ms	±2.8%	1148

Draw 50 rectangles

Benchmark	Mean	p99	RME	Samples
libpdf	292μs	755μs	±1.3%	1712
pdf-lib	1.59ms	6.71ms	±7.2%	315

Load and save PDF

Benchmark	Mean	p99	RME	Samples
libpdf	2.52ms	4.50ms	±2.2%	199
pdf-lib	92.33ms	103.69ms	±6.0%	10

Load, modify, and save PDF

Benchmark	Mean	p99	RME	Samples
libpdf	40.71ms	50.08ms	±6.0%	13
pdf-lib	83.86ms	89.29ms	±2.5%	10

Extract single page from 100-page PDF

Benchmark	Mean	p99	RME	Samples
libpdf	3.48ms	4.00ms	±1.2%	144
pdf-lib	8.98ms	10.86ms	±1.5%	56

Split 100-page PDF into single-page PDFs

Benchmark	Mean	p99	RME	Samples
libpdf	29.71ms	35.65ms	±2.8%	17
pdf-lib	83.15ms	90.87ms	±4.9%	7

Split 2000-page PDF into single-page PDFs (0.9MB)

Benchmark	Mean	p99	RME	Samples
libpdf	552.84ms	552.84ms	±0.0%	1
pdf-lib	1.50s	1.50s	±0.0%	1

Copy 10 pages between documents

Benchmark	Mean	p99	RME	Samples
libpdf	4.33ms	5.04ms	±1.0%	116
pdf-lib	11.63ms	12.67ms	±1.0%	43

Merge 2 x 100-page PDFs

Benchmark	Mean	p99	RME	Samples
libpdf	13.53ms	14.23ms	±0.8%	37
pdf-lib	54.12ms	55.78ms	±1.8%	10

Copying

Copy pages between documents

Benchmark	Mean	p99	RME	Samples
copy 1 page	937μs	2.18ms	±2.9%	534
copy 10 pages from 100-page PDF	4.17ms	6.26ms	±1.9%	120
copy all 100 pages	6.89ms	7.91ms	±0.9%	73

Duplicate pages within same document

Benchmark	Mean	p99	RME	Samples
duplicate page 0	794μs	1.45ms	±1.1%	630
duplicate all pages (double the document)	799μs	1.47ms	±1.2%	627

Merge PDFs

Benchmark	Mean	p99	RME	Samples
merge 2 small PDFs	1.36ms	2.32ms	±1.8%	368
merge 10 small PDFs	7.10ms	10.10ms	±1.8%	71
merge 2 x 100-page PDFs	12.62ms	13.19ms	±0.7%	40

Drawing

benchmarks/drawing.bench.ts

Benchmark	Mean	p99	RME	Samples
draw 100 rectangles	544μs	1.33ms	±2.4%	920
draw 100 circles	1.22ms	2.81ms	±2.8%	412
draw 100 lines	474μs	1.15ms	±1.4%	1055
draw 100 text lines (standard font)	1.53ms	2.29ms	±1.3%	327
create 10 pages with mixed content	1.27ms	2.11ms	±1.6%	394

Forms

benchmarks/forms.bench.ts

Benchmark	Mean	p99	RME	Samples
get form fields	3.02ms	6.28ms	±3.9%	166
fill text fields	10.90ms	15.93ms	±5.0%	46
read field values	2.74ms	4.99ms	±2.0%	183
flatten form	7.78ms	10.70ms	±2.6%	65

Loading

benchmarks/loading.bench.ts

Benchmark	Mean	p99	RME	Samples
load small PDF (888B)	54μs	122μs	±0.7%	9324
load medium PDF (19KB)	85μs	113μs	±0.5%	5887
load form PDF (116KB)	1.44ms	2.60ms	±1.7%	348
load heavy PDF (9.9MB)	2.25ms	2.92ms	±1.1%	223

Saving

benchmarks/saving.bench.ts

Benchmark	Mean	p99	RME	Samples
save unmodified (19KB)	93μs	192μs	±0.7%	5390
save with modifications (19KB)	665μs	1.25ms	±1.5%	752
incremental save (19KB)	133μs	296μs	±0.9%	3769
save heavy PDF (9.9MB)	2.20ms	2.61ms	±0.6%	227
incremental save heavy PDF (9.9MB)	9.01ms	15.08ms	±6.6%	56

Splitting

Extract single page

Benchmark	Mean	p99	RME	Samples
extractPages (1 page from small PDF)	931μs	2.34ms	±3.2%	538
extractPages (1 page from 100-page PDF)	3.34ms	5.78ms	±1.6%	150
extractPages (1 page from 2000-page PDF)	52.89ms	54.04ms	±0.7%	10

Split into single-page PDFs

Benchmark	Mean	p99	RME	Samples
split 100-page PDF (0.1MB)	28.03ms	32.14ms	±3.4%	18
split 2000-page PDF (0.9MB)	529.98ms	529.98ms	±0.0%	1

Batch page extraction

Benchmark	Mean	p99	RME	Samples
extract first 10 pages from 2000-page PDF	55.66ms	60.52ms	±2.8%	9
extract first 100 pages from 2000-page PDF	58.13ms	60.04ms	±1.5%	9
extract every 10th page from 2000-page PDF (200 pages)	63.06ms	74.14ms	±6.0%	8

Environment

• Runner: Linux (X64)
• Runtime: Bun 1.3.10

Results are machine-dependent.