Fallback to embedded font when system font is unsupported

[hecrj]

Fixes #69.

This PR embeds Lato in iced_wgpu and uses it when the default system fonts cannot be handled by rusttype. This is a dirty fix and should increase binary size a bit. It's meant to be a workaround while we move the text pipeline in iced_wgpu to something that offers more support (see #33).

Additionally, the PR also removes the loading of a monospace font, reducing memory footprint. We can use the default font instead for the debug/overlay view.

[safijari]

I just ran into this issue trying to run the examples, found this PR, switched to this branch and recompiled. Still getting a panic.

[hecrj]

@safijari Thanks for testing it!

Could you share a backtrace?

[safijari]

When I run RUST_BACKTRACE=1 cargo run --example tour on 80a8a57 I get:

    Finished dev [unoptimized + debuginfo] target(s) in 0.06s
     Running `target/debug/examples/tour`
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/macros/mod.rs:15:40
stack backtrace:
   0: backtrace::backtrace::libunwind::trace
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/libunwind.rs:88
   1: backtrace::backtrace::trace_unsynchronized
             at /cargo/registry/src/github.com-1ecc6299db9ec823/backtrace-0.3.40/src/backtrace/mod.rs:66
   2: std::sys_common::backtrace::_print_fmt
             at src/libstd/sys_common/backtrace.rs:84
   3: <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt
             at src/libstd/sys_common/backtrace.rs:61
   4: core::fmt::write
             at src/libcore/fmt/mod.rs:1030
   5: std::io::Write::write_fmt
             at src/libstd/io/mod.rs:1412
   6: std::sys_common::backtrace::_print
             at src/libstd/sys_common/backtrace.rs:65
   7: std::sys_common::backtrace::print
             at src/libstd/sys_common/backtrace.rs:50
   8: std::panicking::default_hook::{{closure}}
             at src/libstd/panicking.rs:188
   9: std::panicking::default_hook
             at src/libstd/panicking.rs:205
  10: std::panicking::rust_panic_with_hook
             at src/libstd/panicking.rs:464
  11: std::panicking::continue_panic_fmt
             at src/libstd/panicking.rs:373
  12: rust_begin_unwind
             at src/libstd/panicking.rs:302
  13: core::panicking::panic_fmt
             at src/libcore/panicking.rs:82
  14: core::panicking::panic
             at src/libcore/panicking.rs:50
  15: core::option::Option<T>::unwrap
             at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libcore/macros/mod.rs:15
  16: wgpu_request_adapter
             at /home/jari/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-native-0.4.0/src/instance.rs:474
  17: wgpu::Adapter::request
             at /home/jari/.cargo/registry/src/github.com-1ecc6299db9ec823/wgpu-0.4.0/src/lib.rs:545
  18: iced_wgpu::renderer::Renderer::new
             at wgpu/src/renderer.rs:51
  19: <iced_wgpu::renderer::Renderer as iced_native::renderer::windowed::Windowed>::new
             at wgpu/src/renderer.rs:417
  20: iced_winit::application::Application::run
             at ./winit/src/application.rs:115
  21: iced::application::Application::run
             at ./src/application.rs:140
  22: iced::sandbox::Sandbox::run
             at ./src/sandbox.rs:128
  23: tour::main
             at examples/tour.rs:10
  24: std::rt::lang_start::{{closure}}
             at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/rt.rs:61
  25: std::rt::lang_start_internal::{{closure}}
             at src/libstd/rt.rs:48
  26: std::panicking::try::do_call
             at src/libstd/panicking.rs:287
  27: __rust_maybe_catch_panic
             at src/libpanic_unwind/lib.rs:81
  28: std::panicking::try
             at src/libstd/panicking.rs:265
  29: std::panic::catch_unwind
             at src/libstd/panic.rs:395
  30: std::rt::lang_start_internal
             at src/libstd/rt.rs:47
  31: std::rt::lang_start
             at /rustc/412f43ac5b4ae8c3599e71c6972112e9be4758fa/src/libstd/rt.rs:61
  32: main
  33: __libc_start_main
  34: _start
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.```

[hecrj]

Hey @safijari, thanks for reporting back.

Your issue is not related to font loading. It seems wgpu is not able to find a suitable graphics adapter. A related issue is #72.

My advice is to check that your Vulkan drivers are installed correctly. I am also working on a renderer alternative that should be able to fallback to software mode in this cases.