add `get_default_font` and fix related bugs (#810) #1640

Job	Run time
cargo fmt	14s
Cross-compile (ubuntu-latest, x86_64-unknown-linux-gnu)	1m 35s
Cross-compile (macos-latest, x86_64-apple-darwin)	46s
Cross-compile (windows-latest, x86_64-pc-windows-msvc)	1m 28s
Cross-compile (ubuntu-latest, wasm32-unknown-unknown)	1m 41s
Cross-compile (ubuntu-latest, x86_64-pc-windows-gnu)	1m 27s
	7m 11s

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