ZendPDF, rendering custom fonts

Question

I'm trying to render some "special characters" (⇒⇀↛←⇐⇐↼↚↔⇔⇌⇄⥄) on a new page. When I use the custom TTF "Noto Sans Regular" most of the characters don't render, if I simply swap the font to "Symbola" everything renders exactly as you'd expect.

Is this a known issue in ZendPDF (2.0.2) or am I doing something wrong?

Answer 1

It turns out that the NotoSans font only contained a subset of the characters... lesson learned!