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Add a helper class for building TrueType font tables

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This helps reduce the amount of boilerplate code needed in multiple spots throughout the font code, and more importantly it'll help when building TrueType tables whose final size is non-trivial to compute upfront.
This commit is contained in:
Jonas Jenwald 2026-04-14 15:32:25 +02:00
parent 7f7ac949ff
commit f9ecebe63c
1 changed files with 209 additions and 151 deletions
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360
src/core/fonts.js
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@ -313,43 +313,110 @@ function string16(value) {
return String.fromCharCode((value >> 8) & 0xff, value & 0xff); return String.fromCharCode((value >> 8) & 0xff, value & 0xff);
} }
function setArray(data, pos, arr) { class TrueTypeTableBuilder {
data.set(arr, pos); #buf;
return pos + arr.length;
}
function setInt16(view, pos, val) { #bufLength = 1024;
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
assert(
typeof val === "number" && Math.abs(val) < 2 ** 16,
`setInt16: Unexpected input "${val}".`
);
}
view.setInt16(pos, val);
return pos + 2;
}
function setSafeInt16(view, pos, val) { #hasExactLength = false;
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
assert(
typeof val === "number" && !Number.isNaN(val),
`safeString16: Unexpected input "${val}".`
);
}
// clamp value to the 16-bit int range
view.setInt16(pos, MathClamp(val, -0x8000, 0x7fff));
return pos + 2;
}
function setInt32(view, pos, val) { #pos = 0;
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
assert( #view;
typeof val === "number" && Math.abs(val) < 2 ** 32,
`setInt32: Unexpected input "${val}".` constructor({ exactLength, minLength }) {
); this.#hasExactLength = !!exactLength;
this.#initBuf(exactLength || minLength);
}
#initBuf(minLength) {
if (this.#hasExactLength) {
this.#bufLength = minLength;
} else {
// Compute the first power of two that is as big as the `minLength`.
while (this.#bufLength < minLength) {
this.#bufLength *= 2;
}
}
const newBuf = new Uint8Array(this.#bufLength);
if (this.#buf) {
newBuf.set(this.#buf, 0);
}
this.#buf = newBuf;
this.#view = new DataView(newBuf.buffer);
}
get data() {
return this.#buf.subarray(0, this.#pos);
}
get length() {
return this.#pos;
}
skip(n) {
this.#pos += n;
}
setArray(arr) {
const newPos = this.#pos + arr.length;
if (!this.#hasExactLength && newPos > this.#bufLength) {
this.#initBuf(newPos);
}
this.#buf.set(arr, this.#pos);
this.#pos = newPos;
}
setInt16(val) {
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
assert(
typeof val === "number" && Math.abs(val) < 2 ** 16,
`setInt16: Unexpected input "${val}".`
);
}
const newPos = this.#pos + 2;
if (!this.#hasExactLength && newPos > this.#bufLength) {
this.#initBuf(newPos);
}
this.#view.setInt16(this.#pos, val);
this.#pos = newPos;
}
setSafeInt16(val) {
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
assert(
typeof val === "number" && !Number.isNaN(val),
`safeString16: Unexpected input "${val}".`
);
}
const newPos = this.#pos + 2;
if (!this.#hasExactLength && newPos > this.#bufLength) {
this.#initBuf(newPos);
}
// clamp value to the 16-bit int range
this.#view.setInt16(this.#pos, MathClamp(val, -0x8000, 0x7fff));
this.#pos = newPos;
}
setInt32(val) {
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
assert(
typeof val === "number" && Math.abs(val) < 2 ** 32,
`setInt32: Unexpected input "${val}".`
);
}
const newPos = this.#pos + 4;
if (!this.#hasExactLength && newPos > this.#bufLength) {
this.#initBuf(newPos);
}
this.#view.setInt32(this.#pos, val);
this.#pos = newPos;
} }
view.setInt32(pos, val);
return pos + 4;
} }
function isTrueTypeFile(file) { function isTrueTypeFile(file) {
@ -856,27 +923,24 @@ function createOS2Table(properties, charstrings, override) {
const winAscent = override.yMax || typoAscent; const winAscent = override.yMax || typoAscent;
const winDescent = -override.yMin || -typoDescent; const winDescent = -override.yMin || -typoDescent;
const data = new Uint8Array(96), const os2 = new TrueTypeTableBuilder({ exactLength: 96 });
view = new DataView(data.buffer); os2.setArray([0x00, 0x03]); // version
let pos = 0; os2.setArray([0x02, 0x24]); // xAvgCharWidth
os2.setArray([0x01, 0xf4]); // usWeightClass
pos = setArray(data, pos, [0x00, 0x03]); // version os2.setArray([0x00, 0x05]); // usWidthClass
pos = setArray(data, pos, [0x02, 0x24]); // xAvgCharWidth os2.skip(2); // fstype (0 to improve browser compatibility), skip redundant "\x00\x00"
pos = setArray(data, pos, [0x01, 0xf4]); // usWeightClass os2.setArray([0x02, 0x8a]); // ySubscriptXSize
pos = setArray(data, pos, [0x00, 0x05]); // usWidthClass os2.setArray([0x02, 0xbb]); // ySubscriptYSize
pos += 2; // fstype (0 to improve browser compatibility), skip redundant "\x00\x00" os2.skip(2); // ySubscriptXOffset, skip redundant "\x00\x00"
pos = setArray(data, pos, [0x02, 0x8a]); // ySubscriptXSize os2.setArray([0x00, 0x8c]); // ySubscriptYOffset
pos = setArray(data, pos, [0x02, 0xbb]); // ySubscriptYSize os2.setArray([0x02, 0x8a]); // ySuperScriptXSize
pos += 2; // ySubscriptXOffset, skip redundant "\x00\x00" os2.setArray([0x02, 0xbb]); // ySuperScriptYSize
pos = setArray(data, pos, [0x00, 0x8c]); // ySubscriptYOffset os2.skip(2); // ySuperScriptXOffset, skip redundant "\x00\x00"
pos = setArray(data, pos, [0x02, 0x8a]); // ySuperScriptXSize os2.setArray([0x01, 0xdf]); // ySuperScriptYOffset
pos = setArray(data, pos, [0x02, 0xbb]); // ySuperScriptYSize os2.setArray([0x00, 0x31]); // yStrikeOutSize
pos += 2; // ySuperScriptXOffset, skip redundant "\x00\x00" os2.setArray([0x01, 0x02]); // yStrikeOutPosition
pos = setArray(data, pos, [0x01, 0xdf]); // ySuperScriptYOffset os2.skip(2); // sFamilyClass, skip redundant "\x00\x00"
pos = setArray(data, pos, [0x00, 0x31]); // yStrikeOutSize os2.setArray([
pos = setArray(data, pos, [0x01, 0x02]); // yStrikeOutPosition
pos += 2; // sFamilyClass, skip redundant "\x00\x00"
pos = setArray(data, pos, [
0x00, 0x00,
0x00, 0x00,
0x06, 0x06,
@ -888,46 +952,47 @@ function createOS2Table(properties, charstrings, override) {
0x00, 0x00,
0x00, 0x00,
]); // Panose ]); // Panose
pos = setInt32(view, pos, ulUnicodeRange1); // ulUnicodeRange1 (Bits 0-31) os2.setInt32(ulUnicodeRange1); // ulUnicodeRange1 (Bits 0-31)
pos = setInt32(view, pos, ulUnicodeRange2); // ulUnicodeRange2 (Bits 32-63) os2.setInt32(ulUnicodeRange2); // ulUnicodeRange2 (Bits 32-63)
pos = setInt32(view, pos, ulUnicodeRange3); // ulUnicodeRange3 (Bits 64-95) os2.setInt32(ulUnicodeRange3); // ulUnicodeRange3 (Bits 64-95)
pos = setInt32(view, pos, ulUnicodeRange4); // ulUnicodeRange4 (Bits 96-127) os2.setInt32(ulUnicodeRange4); // ulUnicodeRange4 (Bits 96-127)
pos = setArray(data, pos, [0x2a, 0x32, 0x31, 0x2a]); // achVendID os2.setArray([0x2a, 0x32, 0x31, 0x2a]); // achVendID
pos = setInt16(view, pos, properties.italicAngle ? 1 : 0); // fsSelection os2.setInt16(properties.italicAngle ? 1 : 0); // fsSelection
pos = setInt16(view, pos, firstCharIndex || properties.firstChar); // usFirstCharIndex os2.setInt16(firstCharIndex || properties.firstChar); // usFirstCharIndex
pos = setInt16(view, pos, lastCharIndex || properties.lastChar); // usLastCharIndex os2.setInt16(lastCharIndex || properties.lastChar); // usLastCharIndex
pos = setInt16(view, pos, typoAscent); // sTypoAscender os2.setInt16(typoAscent); // sTypoAscender
pos = setInt16(view, pos, typoDescent); // sTypoDescender os2.setInt16(typoDescent); // sTypoDescender
pos = setArray(data, pos, [0x00, 0x64]); // sTypoLineGap (7%-10% of the unitsPerEM value) os2.setArray([0x00, 0x64]); // sTypoLineGap (7%-10% of the unitsPerEM value)
pos = setInt16(view, pos, winAscent); // usWinAscent os2.setInt16(winAscent); // usWinAscent
pos = setInt16(view, pos, winDescent); // usWinDescent os2.setInt16(winDescent); // usWinDescent
pos += 4; // ulCodePageRange1 (Bits 0-31), skip redundant "\x00\x00\x00\x00" os2.skip(
pos += 4; // ulCodePageRange2 (Bits 32-63), skip redundant "\x00\x00\x00\x00" 4 + // ulCodePageRange1 (Bits 0-31), skip redundant "\x00\x00\x00\x00"
pos = setInt16(view, pos, properties.xHeight); // sxHeight 4 // ulCodePageRange2 (Bits 32-63), skip redundant "\x00\x00\x00\x00"
pos = setInt16(view, pos, properties.capHeight); // sCapHeight );
pos += 2; // usDefaultChar, skip redundant "\x00\x00" os2.setInt16(properties.xHeight); // sxHeight
pos = setInt16(view, pos, firstCharIndex || properties.firstChar); // usBreakChar os2.setInt16(properties.capHeight); // sCapHeight
setArray(data, pos, [0x00, 0x03]); // usMaxContext os2.skip(2); // usDefaultChar, skip redundant "\x00\x00"
os2.setInt16(firstCharIndex || properties.firstChar); // usBreakChar
return data; os2.setArray([0x00, 0x03]); // usMaxContext
return os2.data;
} }
function createPostTable(properties) { function createPostTable(properties) {
const data = new Uint8Array(32), const post = new TrueTypeTableBuilder({ exactLength: 32 });
view = new DataView(data.buffer); post.setArray([0x00, 0x03, 0x00, 0x00]); // Version number
let pos = 0; post.setInt32(Math.floor(properties.italicAngle * 2 ** 16)); // italicAngle
post.skip(
pos = setArray(data, pos, [0x00, 0x03, 0x00, 0x00]); // Version number 2 + // underlinePosition, skip redundant "\x00\x00"
pos = setInt32(view, pos, Math.floor(properties.italicAngle * 2 ** 16)); // italicAngle 2 // underlineThickness, skip redundant "\x00\x00"
pos += 2; // underlinePosition, skip redundant "\x00\x00" );
pos += 2; // underlineThickness, skip redundant "\x00\x00" post.setInt32(properties.fixedPitch ? 1 : 0); // isFixedPitch
setInt32(view, pos, properties.fixedPitch ? 1 : 0); // isFixedPitch post.skip(
// minMemType42, skip redundant "\x00\x00\x00\x00" 4 + // minMemType42, skip redundant "\x00\x00\x00\x00"
// maxMemType42, skip redundant "\x00\x00\x00\x00" 4 + // maxMemType42, skip redundant "\x00\x00\x00\x00"
// minMemType1, skip redundant "\x00\x00\x00\x00" 4 + // minMemType1, skip redundant "\x00\x00\x00\x00"
// maxMemType1, skip redundant "\x00\x00\x00\x00" 4 // maxMemType1, skip redundant "\x00\x00\x00\x00"
);
return data; return post.data;
} }
function createPostscriptName(name) { function createPostscriptName(name) {
@ -3299,29 +3364,28 @@ class Font {
"head", "head",
(function fontTableHead() { (function fontTableHead() {
const dateArr = [0x00, 0x00, 0x00, 0x00, 0x9e, 0x0b, 0x7e, 0x27]; const dateArr = [0x00, 0x00, 0x00, 0x00, 0x9e, 0x0b, 0x7e, 0x27];
const data = new Uint8Array(54),
view = new DataView(data.buffer);
let pos = 0;
pos = setArray(data, pos, [0x00, 0x01, 0x00, 0x00]); // Version number const head = new TrueTypeTableBuilder({ exactLength: 54 });
pos = setArray(data, pos, [0x00, 0x00, 0x10, 0x00]); // fontRevision head.setArray([0x00, 0x01, 0x00, 0x00]); // Version number
pos += 4; // checksumAdjustement, skip redundant "\x00\x00\x00\x00" head.setArray([0x00, 0x00, 0x10, 0x00]); // fontRevision
pos = setArray(data, pos, [0x5f, 0x0f, 0x3c, 0xf5]); // magicNumber head.skip(4); // checksumAdjustement, skip redundant "\x00\x00\x00\x00"
pos += 2; // Flags, skip redundant "\x00\x00" head.setArray([0x5f, 0x0f, 0x3c, 0xf5]); // magicNumber
pos = setSafeInt16(view, pos, unitsPerEm); // unitsPerEM head.skip(2); // Flags, skip redundant "\x00\x00"
pos = setArray(data, pos, dateArr); // creation date head.setSafeInt16(unitsPerEm); // unitsPerEM
pos = setArray(data, pos, dateArr); // modifification date head.setArray(dateArr); // creation date
pos += 2; // xMin, skip redundant "\x00\x00" head.setArray(dateArr); // modifification date
pos = setSafeInt16(view, pos, properties.descent); // yMin head.skip(2); // xMin, skip redundant "\x00\x00"
pos = setArray(data, pos, [0x0f, 0xff]); // xMax head.setSafeInt16(properties.descent); // yMin
pos = setSafeInt16(view, pos, properties.ascent); // yMax head.setArray([0x0f, 0xff]); // xMax
pos = setInt16(view, pos, properties.italicAngle ? 2 : 0); // macStyle head.setSafeInt16(properties.ascent); // yMax
setArray(data, pos, [0x00, 0x11]); // lowestRecPPEM head.setInt16(properties.italicAngle ? 2 : 0); // macStyle
// fontDirectionHint, skip redundant "\x00\x00" head.setArray([0x00, 0x11]); // lowestRecPPEM
// indexToLocFormat, skip redundant "\x00\x00" head.skip(
// glyphDataFormat, skip redundant "\x00\x00" 2 + // fontDirectionHint, skip redundant "\x00\x00"
2 + // indexToLocFormat, skip redundant "\x00\x00"
return data; 2 // glyphDataFormat, skip redundant "\x00\x00"
);
return head.data;
})() })()
); );
@ -3329,33 +3393,31 @@ class Font {
builder.addTable( builder.addTable(
"hhea", "hhea",
(function fontTableHhea() { (function fontTableHhea() {
const data = new Uint8Array(36), const hhea = new TrueTypeTableBuilder({ exactLength: 36 });
view = new DataView(data.buffer); hhea.setArray([0x00, 0x01, 0x00, 0x00]); // Version number
let pos = 0; hhea.setSafeInt16(properties.ascent); // Typographic Ascent
hhea.setSafeInt16(properties.descent); // Typographic Descent
pos = setArray(data, pos, [0x00, 0x01, 0x00, 0x00]); // Version number hhea.skip(2); // Line Gap, skip redundant "\x00\x00"
pos = setSafeInt16(view, pos, properties.ascent); // Typographic Ascent hhea.setArray([0xff, 0xff]); // advanceWidthMax
pos = setSafeInt16(view, pos, properties.descent); // Typographic Descent hhea.skip(
pos += 2; // Line Gap, skip redundant "\x00\x00" 2 + // minLeftSidebearing, skip redundant "\x00\x00"
pos = setArray(data, pos, [0xff, 0xff]); // advanceWidthMax 2 + // minRightSidebearing, skip redundant "\x00\x00"
pos += 2; // minLeftSidebearing, skip redundant "\x00\x00" 2 // xMaxExtent, skip redundant "\x00\x00"
pos += 2; // minRightSidebearing, skip redundant "\x00\x00" );
pos += 2; // xMaxExtent, skip redundant "\x00\x00" hhea.setSafeInt16(properties.capHeight); // caretSlopeRise
pos = setSafeInt16(view, pos, properties.capHeight); // caretSlopeRise hhea.setSafeInt16(
pos = setSafeInt16(
view,
pos,
Math.tan(properties.italicAngle) * properties.xHeight Math.tan(properties.italicAngle) * properties.xHeight
); // caretSlopeRun ); // caretSlopeRun
pos += 2; // caretOffset, skip redundant "\x00\x00" hhea.skip(
pos += 2; // -reserved-, skip redundant "\x00\x00" 2 + // caretOffset, skip redundant "\x00\x00"
pos += 2; // -reserved-, skip redundant "\x00\x00" 2 + // -reserved-, skip redundant "\x00\x00"
pos += 2; // -reserved-, skip redundant "\x00\x00" 2 + // -reserved-, skip redundant "\x00\x00"
pos += 2; // -reserved-, skip redundant "\x00\x00" 2 + // -reserved-, skip redundant "\x00\x00"
pos += 2; // metricDataFormat, skip redundant "\x00\x00" 2 + // -reserved-, skip redundant "\x00\x00"
setInt16(view, pos, numGlyphs); // Number of HMetrics 2 // metricDataFormat, skip redundant "\x00\x00"
);
return data; hhea.setInt16(numGlyphs); // Number of HMetrics
return hhea.data;
})() })()
); );
@ -3366,10 +3428,9 @@ class Font {
const charstrings = font.charstrings; const charstrings = font.charstrings;
const cffWidths = font.cff?.widths ?? null; const cffWidths = font.cff?.widths ?? null;
const data = new Uint8Array(numGlyphs * 4), const hmtx = new TrueTypeTableBuilder({ exactLength: numGlyphs * 4 });
view = new DataView(data.buffer);
// Fake .notdef (width=0 and lsb=0) first, skip redundant assignment. // Fake .notdef (width=0 and lsb=0) first, skip redundant assignment.
let pos = 4; hmtx.skip(4);
for (let i = 1, ii = numGlyphs; i < ii; i++) { for (let i = 1, ii = numGlyphs; i < ii; i++) {
let width = 0; let width = 0;
@ -3378,10 +3439,10 @@ class Font {
} else if (cffWidths) { } else if (cffWidths) {
width = Math.ceil(cffWidths[i] || 0); width = Math.ceil(cffWidths[i] || 0);
} }
pos = setInt16(view, pos, width); hmtx.setInt16(width);
pos += 2; // Use lsb=0, skip redundant assignment. hmtx.skip(2); // Use lsb=0, skip redundant assignment.
} }
return data; return hmtx.data;
})() })()
); );
@ -3389,13 +3450,10 @@ class Font {
builder.addTable( builder.addTable(
"maxp", "maxp",
(function fontTableMaxp() { (function fontTableMaxp() {
const data = new Uint8Array(6), const maxp = new TrueTypeTableBuilder({ exactLength: 6 });
view = new DataView(data.buffer); maxp.setArray([0x00, 0x00, 0x50, 0x00]); // Version number
maxp.setInt16(numGlyphs); // Num of glyphs
setArray(data, 0, [0x00, 0x00, 0x50, 0x00]); // Version number return maxp.data;
setInt16(view, 4, numGlyphs); // Num of glyphs
return data;
})() })()
); );