Idiomatic Rust

[matprec]

Wouldn't it be more idiomatic to return Result instead of asserting hr == 0 all over the place?

Not exposing the abillity to fail and instead panicing makes the api unidiomatic in my opinion, since e.g. FontDescriptor can be manipulated by the user, which in turn can cause hr != 0.

[vvuk]

Probably -- the way the code evolved the hr == 0 assertions just lived on through. I'm open to making this API change later on. Note that things that can safely fail such as get_font_from_descriptor and stuff like FontCollection::get_font_family_by_name return Option. They only panic in case of bad/usage failure (I think). For example, calling FontCollection::get_font_family with an index that's out of range causes an assertion failure/panic.