post table is created with defaults when calling toArrayBuffer

[cthorner]

Expected Behavior

calling toArrayBuffer should create a font that has the same post table as the font it was created from

since the post table is created from scratch with defaults with post.make() things like underlineThickness and underlinePosition
are always set to 0 instead of using the values from the original post table

Here is the offending code:

opentype.js/src/tables/sfnt.js

Line 289 in 2a6c2f6

const postTable = post.make();

I would expect something like this:

opentype.js/src/tables/sfnt.js

Line 309 in 2a6c2f6

tables.push(gsub.make(font.tables.gsub));

opentype.js/src/tables/sfnt.js

Line 312 in 2a6c2f6

tables.push(cpal.make(font.tables.cpal));

opentype.js/src/tables/sfnt.js

Line 315 in 2a6c2f6

tables.push(colr.make(font.tables.colr));

Current Behavior

font.toArrayBuffer() creates font with post table defaults

Possible Solution

parse values from the font's post table to create the new set of tables

Steps to Reproduce (for bugs)

load a font with a value for tables.post.underlineThickness != 0
call:
font.toArrayBuffer()
use the font with underline, see that it is not underlined

Context

have working underlining in an SVG

Your Environment

• Version used: 1.3.4
• Font used: any font
• Browser Name and version: N/A
• Operating System and version (desktop or mobile): N/A
• Link to your project: N/A