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Use a TypedArray when building the "hmtx" font table

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In this case it's trivial to compute the size of the data upfront, hence we can use a TypedArray which should be more efficient than a string.
This commit is contained in:
Jonas Jenwald 2026-04-09 18:58:58 +02:00
parent 9efd9fa2c7
commit 8f56ee2ae9
1 changed files with 12 additions and 6 deletions
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18
src/core/fonts.js
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@ -3311,19 +3311,25 @@ class Font {
"hmtx",
(function fontFieldsHmtx() {
const charstrings = font.charstrings;
const cffWidths = font.cff ? font.cff.widths : null;
let hmtx = "\x00\x00\x00\x00"; // Fake .notdef
const cffWidths = font.cff?.widths ?? null;
const data = new Uint8Array(numGlyphs * 4);
// Fake .notdef (width=0 and lsb=0) first, skip redundant assignment.
let pos = 4;
for (let i = 1, ii = numGlyphs; i < ii; i++) {
let width = 0;
if (charstrings) {
const charstring = charstrings[i - 1];
width = "width" in charstring ? charstring.width : 0;
width = charstrings[i - 1].width || 0;
} else if (cffWidths) {
width = Math.ceil(cffWidths[i] || 0);
}
hmtx += string16(width) + string16(0);
data[pos++] = (width >> 8) & 0xff;
data[pos++] = width & 0xff;
// Use lsb=0, skip redundant assignment.
pos += 2;
}
return hmtx;
return data;
})()
);