The single_glyph example might crash

[baskerville]

Steps to reproduce:

cargo run --example single_glyph DejaVuSans-Oblique.ttf A

[lucklove]

In my tests(debug mode), It not work with these characters: ['A' , 'J', 'X', 'Z', 'p', 'x', 'y', 'z', ...], the crash message is:

cargo run --example single_glyph DejaVuSans-Oblique.ttf A
    Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
     Running `target/debug/examples/single_glyph DejaVuSans-Oblique.ttf A`
thread 'main' panicked at 'attempt to add with overflow', examples/single_glyph.rs:14
note: Run with `RUST_BACKTRACE=1` for a backtrace.

It seems there is an usize overflow.

[baskerville]

Yes, glyph.bitmap_left() can be negative.