Fonts prohibiting installable embedding

[Marcel Fabian Krüger]

Hi,

On Mon, Oct 04, 2021 at 07:24:53PM -0700, Felix Lechner wrote:
> > I am confused why there needs to be both Opentype.pm and Truetype.pm
> > files.
> 
> That's only temporary. As far as I understand, TrueType and OpenType
> are two different but related standards that were written sixteen
> years apart. OpenType shares many similarities but also offers
> additional features.

If I understand Opentype.pm and Truetype.pm correctly, then basically
a font is handled by Truetype.pm if `file` reports it as "TrueType Font
data" and Opentype.pm is it's reported as "OpenType Font file", right?

This is based on the file header which in turn is based on the outline
format in the font, not on the followed standard. Well, the old
TrueType standard only allowed TrueType outlines, but the OpenType
standard allows both TrueType outlines (which then get reported as
"TrueType Font data" is if new OpenType features are used) and CFF
outlines (which get reported as "OpenType Font data").
Also there are color fonts which contain neither kind of outlines and
therefore it is unspecified which header is used for them, but in most
cases they end up being reported as "TrueType Font data" too, even
though they certainly don't follow the TrueType standard.

Therefore the distinction as it's done by these files is rather
artificial.
Related to that: The Truetype.pm file checks that the file extension
is `.ttf`, but the OpenType specification explicitly allows TrueType
based OpenType fonts (which get reported as "TrueType font data") to
use the `.otf` file extension.

Best,
Marcel