PDFKit crashes when providing fonts as Buffer in table

[ykw9263]

Bug Report

Description of the problem

When providing font in table cells with a src of Buffer or UintArray, Not a supported font format or standard PDF font. will be thrown.

Upon some digging, I found that in normalizeCell() the font object is deep-merged with other fonts in table styles

pdfkit/lib/table/normalize.js

Line 96 in 2fdafa2

const font = deepMerge({}, colStyle.font, rowStyle.font, cell.font);

This line took an unusually long time to execute, and after this the font src became something like

console.log(font.src)
// { '1': number, '2': number, '3': number, ... }

Code sample

import PDFDocument from "pdfkit";
import fs from "fs";
const doc = new PDFDocument();

doc.table().row([
  {
    text: 'Hello World',
    font: { src: fs.readFileSync(SOME_CUSTOM_FONT), family: FONT_FAMILY },
  }
])

Possible fix

Replace the font deep merge with manual property assignment.
Considering the structure of the font object a shallow merge may also be enough.

// changing to this worked properly in my case
const font = {...colStyle.font, ...rowStyle.font, ...cell.font}

Your environment

• pdfkit version: 0.19.1
• Node version: 24.15.0
• Browser version (if applicable): N/A
• Operating System: Windows 11

[ykw9263]

A workaround is to register the font with registerFont and use the alias in table cell font, like below

import PDFDocument from "pdfkit";
import fs from "fs";
const doc = new PDFDocument();

doc.registerFont(ALIAS, SOME_CUSTOM_FONT, FONT_FAMILY);

doc.table().row([
  {
    text: 'Hello World',
    font: { src: ALIAS },
  }
])

[blikblum]

const font = {...colStyle.font, ...rowStyle.font, ...cell.font}

Please, open a PR with this change

@hollandjake any thoughts?

[ykw9263]

Thanks, I will fork and open one.

btw seems that putting font buffer in columnStyles and rowStyles have the same issue even with the suggested fix.
The DefinitelyTyped type definitions didn't include fonts options in columnStyles or rowStyles though.

[blikblum]

btw seems that putting font buffer in columnStyles and rowStyles have the same issue even with the suggested fix.
The DefinitelyTyped type definitions didn't include fonts options in columnStyles or rowStyles though.

@hollandjake is this by design?

[hollandjake]

@blikblum definitely sounds unintentional

[blikblum]

I examined the font loading and concluded that allowing passing font buffer to font.src options in table row options is a foot gun.

Doing:

const fontBuffer = fs.readFileSync(SOME_CUSTOM_FONT)
doc.table().row([{
    text: 'Row 1',
    font: { src: fontBuffer },
  }]).row([{
    text: 'Row 2',
    font: { src: fontBuffer },
  }]).row([{
    text: 'Row 3',
    font: { src: fontBuffer },
  }])

Would load 3 different font instances

So i'm leaning toward only allowing font aliases on table styles. To be fair, the font option in table is not documented at all so is just a matter of documentation

[ykw9263]

I haven't look deeper into the font loading mechanism yet. Does these lines deduplicates font buffers before loading?

pdfkit/lib/mixins/fonts.js

Lines 87 to 95 in 0036303

	// check for existing font familes with the same name already in the PDF
	// useful if the font was passed as a buffer
	if (
	(font = this._fontFamilies[this._font.name]) &&
	isEqualFont(this._font, font)
	) {
	this._font = font;
	return this;
	}

My original use case was to make something like table builder that supports providing fonts with Uint8arrays as the font may be fetched from online sources. Registering an alias for the font would require hashing the buffer or extracting the font name from the buffer if I want the alias not to duplicate.

[ykw9263]

btw seems that putting font buffer in columnStyles and rowStyles have the same issue even with the suggested fix.
The DefinitelyTyped type definitions didn't include fonts options in columnStyles or rowStyles though.

@hollandjake is this by design?

By the PDFKit documentation on Tables Column options and Row options extends Cell options, which includes options for font. So I guess it was a miss

[blikblum]

I haven't look deeper into the font loading mechanism yet. Does these lines deduplicates font buffers before loading?

One line above the font instance is created. This code, AFAIK, does not save any resource

[ykw9263]

Oh so at best it will just skip the font registeration on duplicated font buffers. At least GC seems working so the concern is the expensive font creation and comparison. The problem worsens when using column / row options as the font buffer will be applied on every affected cell

So i'm leaning toward only allowing font aliases on table styles. To be fair, the font option in table is not documented at all so is just a matter of documentation

The unsupported font error somehow makes sense now :p

[blikblum]

Using family prop togetther with src: buffer will avoid the font creation every time