Derive Macro VisualContext 

#[derive(VisualContext)]
{
    // Attributes available to this derive:
    #[window]
    #[app]
}

#[derive(VisualContext)] is used to create a visual context out of anything that holds a &mut Window and implements AppContext Note that a #[app] and a #[window] attribute are required to identify the variables holding the &mut App, and &mut Window respectively.

Failure to add both attributes causes a compile error:

#[derive(VisualContext)]
struct MyContext<'a, 'b> {
    #[app]
    app: &'a mut gpui::App,
    window: &'b mut gpui::Window
}

#[derive(VisualContext)]
struct MyContext<'a, 'b> {
    app: &'a mut gpui::App,
    #[window]
    window: &'b mut gpui::Window
}