How do I use multiple fonts ie a composite font in HexaPDF - ruby

Question

Our users are giving us Emoji and a lot of other weird characters and the built-in Helvetica can't handle it. Neither can Google's Noto fonts by themselves - I need to figure out how to declare the Noto Font Family in HexaPDF and I can't figure out how to do that with the given documentation. OpenSans was an improvement, but I still want more glyph coverage than that.
Update:
I used this method to set the font:
def self.pdf_summary_font
##pdf_summary_font ||= File.open(Rails.root.join('public',
'OpenSansEmoji.ttf'), 'r')
end
canvas = page.canvas(type: :overlay)
canvas.font(self.class.pdf_summary_font, size: 10)
However, no Noto font ever worked with this - I would get errors like "Missing glyph - 'A'"
The best I could do was to use OpenSansEmoji, and replace missing glyphs with the following block:
begin
style = HexaPDF::Layout::Style.new(font: canvas.font, fill_color: color, stroke_color: color, align: :left, valign: :center)
fragment = HexaPDF::Layout::TextFragment.create(str, style)
layouter = HexaPDF::Layout::TextLayouter.new(style)
layouter.fit([fragment], w, h).draw(canvas, x1, y2)
rescue HexaPDF::Error => e
if e.message.include?('Glyph for')
glyph = e.message.match(/\{(.*?)\}/).captures.first
str = str.grapheme_clusters.map do |char|
if char.dump.include?(glyph)
"\u{FFFD}"
else
char
end
end.join
retry
end

Answer 1

Have a look at https://hexapdf.gettalong.org/documentation/reference/api/HexaPDF/index.html and the configuration option "font_map". This allows you to declare any TrueType file and use it.
You could also use the path to the font file directly with the Canvas#font method.
If you need to cover a wide array of characters you need to use a single font that covers all of them, one of the fonts included in this ZIP file should probably work (Google says 582 languages, 237 regions included).