Writing slow (30+ seconds) for certain fonts (CJK, Noto Chinese)

[Balearica]

For most fonts, Opentype.js can write a font file using font.download() or font.toArrayBuffer() in a fraction of a second. However, certain fonts that include many characters are subject to extreme runtimes.

This occurs with both Simplified Chinese variants of the Noto family. Using NotoSansSC-Regular.ttf (available here), running font.toArrayBuffer() from the console after loading in the example site took 36 seconds. Similarly, trying to write NotoSerifSC-Regular.otf (available here) running font.toArrayBuffer() took 33 seconds.

Not all CJK fonts are this slow--I tested a couple others from Google Fonts that took 4-5 seconds. However, as I've never experienced anything like this with fonts that only support Latin characters, I'm guessing it's related to the number of glyphs in these fonts.

I will investigate more myself and try and fix in a PR.

Your Environment

• Version used: 3fce140
  • Latest commit as of the time of this writing
• Font used: Noto Sans Simplified Chinese, Noto Serif Simplified Chinese
• Browser Name and version: Chrome
• Operating System and version (desktop or mobile): Windows 10

[Balearica]

This ended up being due to excessive re-allocation of memory by using d = d.concat(...) rather than push. This is fixed in the PR linked above.

[Connum]

Closed via #683