add `get_default_font` and fix related bugs #1503

Job	Run time
cargo fmt	9s
Cross-compile (ubuntu-latest, x86_64-unknown-linux-gnu)	1m 15s
Cross-compile (ubuntu-latest, x86_64-pc-windows-gnu)	1m 13s
Cross-compile (ubuntu-latest, wasm32-unknown-unknown)	58s
Cross-compile (macos-latest, x86_64-apple-darwin)	56s
Cross-compile (windows-latest, x86_64-pc-windows-msvc)	2m 15s
	6m 46s

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