get_context

browser_video_capture

Macro get_context 

Source 
macro_rules! get_context {
    ("2d" $name:literal, $canvas:expr, $options:expr) => { ... };
    ("webgl" $name:literal, $canvas:expr, $options:expr) => { ... };
    ("webgl2" $name:literal, $canvas:expr, $options:expr) => { ... };
}